Getting Quick Cash for Your Structured Settlement

Just because you received a structured settlement for your lawsuit, it doesn't mean you have to wait for years to get the money. There are many settlement purchasing companies that will give you instant cash for your structured settlement. These companies can pay cash for the entire structured settlement or purchase your remaining periodic settlement payments. You can spend this lump-sum payment on anything-a house, college tuition, business investments or debts.
What Is a Structured Settlement?
A structured settlement, which typically results from a personal injury lawsuit, is an agreement where you consent to accept payments over time in exchange for the release of liability for your claim. A structured settlement can provide payments in almost any manner you choose. For example, the settlement may be paid in annual installments over a number of years or in periodic payouts every few years.
These payments are generally awarded through the purchase of one or more annuities from a life insurance company. Structured settlements can also be used with lottery winnings, contest prize money and other situations with substantial cash awards.
Structured Settlements Not Always the Best Fit
In theory, structured settlements are designed to provide long-term financial security to injury victims through tax-free payments. And for most people, the agreed-upon structured payment plan initially makes sense. However, a financial emergency, a business opportunity, an unforeseen medical expense, or a house purchase can put a strain on the injured party's finances.
And the structured nature of the settlement may become too restrictive to cover major financial purchases. Also, a structured settlement may not be the best option for investing. There are many other investment vehicles that can generate greater long-term return than the annuities used in structured settlements. Therefore, some people may be better off getting cash for their structured settlement and then building their own investment portfolio.
How Getting Cash for a Structured Settlement Works
If you receive an award from your injury case, an attorney or financial advisor will likely recommend setting up periodic installment payments instead of giving you a lump sum of cash up front for your structured settlement. Then, an independent third party will purchase an annuity that will provide you with tax-free periodic payments.
Companies that offer cash for structured settlements have a variety of programs that can allow you to access any portion of your annuity. For example, you may want to sell as little as four year's worth of payments or receive a lump-sum payment while still enjoying some portion of your monthly payment. Or you can sell your settlement for a large payment that is five or six years in the future. You can also customize an arrangement to get cash for a structured settlement based on your unique needs.
Here's an example of how obtaining cash for a structured settlement works: Let's say you were in an accident five years ago. The accident caused you to be hospitalized for several months and undergo nearly a year's worth of physical therapy. So you hired an attorney and sued the responsible individual-or, rather, the person's insurance company. Ultimately, your attorney advises you that you'll be awarded a substantial sum of money.
After several months or years of negotiation, you receive a sizable settlement. However, the cash you get upfront is only enough to cover the medical expenses. The rest of your compensation is scheduled to be paid out in regular installments through an annuity over the next 15 to 30 years. Rather than being restricted to monthly or annual payments, you contact a settlement purchaser to secure immediate cash for your structured settlement. You're then able to use the cash to enhance your current cash flow-rather than waiting on periodic future payments.
Legal Issues of Receiving Cash for a Structured Settlement
If you're contemplating getting cash for your structured settlement, it's important to contact a financial advisor. Most states have regulations that limit the sale of structured settlements, so you'll need court approval to receive cash for your structured settlement. Federal restrictions also may affect the sale of structured settlements to a third-party individual. And some insurance companies won't transfer annuities to third parties.
Also, before you attempt to obtain cash for a structured settlement, be sure to do your homework. Check out multiple companies to see which one can offer you the most cash for your structured settlement. You also want to examine their integrity, reputation and track record. This will help ensure you have the most positive experience obtaining cash for your structured settlement.

How to Design Fabric Structures

A fabric structures is membrane/ or fabric under prestress ( tension ) stage. A structural elements and supporting system required to maintain the tension form. Two shapes are evident in tension fabric structures.
A. Anticlastic structures with two double in opposite curvature. These type of structuresShape carried many free tension fabric forms. Example of pure tensile fabric structures.
B. Synclastic structures with two double curvatures in the same direction. Example of Air supported structures.
Anticlastic curves take a wide variety of free forms but are commonly made up from some basic shapes. The fabric structures form are cone, arched vault and the hypar.
The Cone
- Single cone, multiples cones, fixed edge at the parameter of cone, catenary edges/ or cables edge at the parameter of the cone, variations in overall peak heights, or inverted cone (cone upside down).
The Arched Vault
- Parallel arches or crossed arches.
The Hyper -
- Two opposing high points and two opposing low points.
Fabric structures give natural diffuse light but with reduced heat load. The high reflectivity of the white membrane fabric is very efficient. An very good alternative to polycarbonate or glass as a roof glazingsystem.
Light penetrates into tensile fabric membrane with natural light and at night the artificial light provide an ambience of great appeal to many people.
In day time the light transmission is typically 5% - 20%, it is just sufficient to eliminate or greatly reduce the need for artificial lighting in day time. With little or no artificial lighting a heat load is reduced. Absorption of solar energy in the fabric structures is typically 4% to 17%.
With colored fabrics, in particularly dark colored fabric membranes, the absorption of heat is very high and the re?radiated effect can be strong and therefore unpleasant. For this reason white should be chosen for enclosed or shade structures in tensile fabric structures application.
Fabric structures offer both the roof and the cladding in one element, the tensile membrane structures provides all of this in one structural element. Therefore the structural element is important for structural appearance: -
(a) Seam and Curve in the tensile fabric structures reflect tension forces hence create eye catching character.
(b) Structure, lighting, fire sprinkle and other expose elements in the space compliment each other.
Some of the practical advantages of Tension Fabric Structures are:
(c) low maintenance compare to glass;
(d) factory manufacture of the membrane minimizing site interruptions;
(e) Membrane factory welded into single weatherproof skin eliminating expansion joints;
(f) large span with more coverage;
(g) Designed for rapid construction.
REINFORCED FABRIC MEMBRANE TYPES
Two fabric membrane types are commonly used in tension fabric structures:
I PVDF/PVC Coated Polyester
(Polyvinyl DeneFlouride)
II PTFE Coated Fiberglass
(PolyTetraFluoroEthylene)
I TENSILE FABRIC STRUCTURES - PVC COATED POLYESTER
This material has been widely used for fabric structures for over twenty years. The material is easily handled and welded using fabric structures high frequency welders. International convention has defined four grades of fabric based on mechanical properties, weights and strengths increase up to grade IV. The project engineers usually make fabric selection after shape analysis. The grading and types depend on fabric manufacturers.
There are several types of PVC fabrics classified according to surface coatings see below.
The PVC coated polyester fabrics offer significant cost advantages over PTFE coated Fiberglass fabrics.
The life span of a PVC coated polyester architectural fabric should exceed fifteen years.
(a) Acrylic Typically used where the fabric is colored. This type of fabric does not have as good properties for self cleaning or for life expectancy as compared with PVDF or PTFE fabrics. Acrylic coated can be welded conventionally without any surface treatment. Warranty 3-5 years and for smaller structure.
(b) PVDF (Polyvinyl DeneFlouride) coating This coating has excellent theoretical properties for long term clean ability and protects the PVC and polyester. All architectural fabric should be specified with antiwick base fabrics. Wicking is the problem where water creeps internally along the thread lines of the fabric leading to unsightly staining of the fabric and possible de lamination. Warranty for 7-12 years depend type and made of fabric.
II TENSILE FABRIC STRUCTURES - PTFE (PolyTetraFluoroEthylene ) COATED FIBREGLASS
PTFE is chemically inert and offers excellent self cleaning properties, fire resistance and life span life spans typically exceed twenty five years.
PTFE coated Fiberglass is very expensive but is competitive with glass. The main problem with PTFE is that it requires very careful handling during the construction phase. The installation of PTFE coated Fiberglass fabric requires much more care and more complex detailing than the PVC coated polyester fabrics.
The fabric for tension fabric structures is not weldable with conventional high frequency equipment but uses a special iron. Particular properties of PTFE allow it to be welded and unwelded using the same machinery. This allows damaged panels to be repaired on site.

Financial Security through Structured Settlements

Structured settlements have become a natural part of personal injury and worker's compensation claims in the United States, according to the National Structured Settlements Trade Association (NSSTA). In 2001, life insurance members of NSSTA wrote more than $6.05 billion of issued annuities as settlement for physical injury claims. This represents a 19 percent increase over 2000.
A structured settlement is the dispersement of money for a legal claim where all or part of the arrangement calls for future periodic payments. The money is paid in regular installments--annually, semi-annually or quarterly--either for a fixed period or for the lifetime of the claimant. Depending on the needs of the individual involved, the structure may also include some immediate payment to cover special damages. The payment is usually made through the purchase of an annuity from a Life Insurance Company.
A structured settlement structure can provide long-term financial security to injury victims and their families through a stream of tax-free payments tailored to their needs. Historically, they were first utilized in Canada and the United States during the 1970s as an alternative to lump-sum payments for injured parties. A structured settlement can also be used in situations involving lottery winnings and other substantial funds.
How a Structured Settlement Works
When a plaintiff settles a case for a large sum of money, the defendant, the plaintiff's attorney, or a financial planner may propose paying the settlement in installments over time rather than in a single lump sum.
A structured settlement is actually a tradeoff. The individuals who were injured and/or their parents or guardians work with their lawyer and an outside broker to determine future medical and living needs. This includes all upcoming operations, therapy, medical devices and other health care needs. Then, an annuity is purchased and held by an independent third party that makes payments to the person who has been injured. Unlike stock dividends or bank interest, these structured settlement payments are completely tax-free. What's more, the individual's annuity grows tax-free.
Pros and Cons
As with anything, there's a positive and negative side to structure settlements. One significant advantage is tax avoidance. When appropriately set up, a structured settlement may significantly reduce the plaintiff's tax obligations (as a result of the settlement). Another benefit is that a structured settlement can help ensure a plaintiff has the funds to pay for future care or needs. In other words, a structured settlement can help protect a plaintiff from himself.
Let's face it: Some people have a hard time managing money, or saying no to friends and family wanting to "share the wealth." Receiving money in installment can make it last longer.
A downside to structure settlements is the built-in structure (no pun intended). Some people may feel restricted by periodic payments. For example, they may want to buy a new home or other expensive item, yet lack the funds to do so. They can't borrow against future payments under their settlement, so they're stuck until their next installment payment arrives.
And from an investment perspective, a structured settlement may not make the most sense for everyone. Many standard investments can provide a greater long-term return than the annuities used in structured settlements. So some people may be better off accepting a lump sum settlement and then investing it for themselves.
Here are some other important points to keep in mind about structured settlements: An injured person with long-term special needs may benefit from having periodic lump sums to purchase medical equipment. Minors may benefit from a structured settlement that provides for certain costs when they're young--such as educational expenses--instead of during adulthood.
Special Considerations
- Injured parties should be wary of potential exploitation or hazards related to structured settlements. They should carefully consider:
- High Commissions - Annuities can be highly profitable for insurance companies, and they often carry very large commissions. It is important to ensure that the commissions charged in setting up a structured settlement don't eat up too much of its principal.
- Inflated Value - Sometimes, the defense will overstate the value of a negotiated structured settlement. As a result, the plaintiff winds up with much less than was agreed upon. Plaintiffs should compare the fees and commissions charged for similar settlement packages by a variety of insurance companies to make sure that they're getting full value.
- Conflict of Interest - There have been situations where the plaintiff's attorney has referred the client to a particular financial planner to set up a structured settlement, without disclosing he would receive a referral fee. In other cases, the plaintiff's lawyer has set up a structured settlement on behalf of a client without revealing the annuities are being purchased from his own insurance business. Plaintiffs should know what financial interest their lawyer may have in relation to any financial services being provided or recommended.
- Using Multiple Insurance Companies - It's advisable to purchase annuities for a structured settlement from several different companies. This offers protection in the event a company that issued annuities for a settlement package goes into bankruptcy and defaults.
Benefits of Selling A Settlement
A structured settlement is specifically designed to meet the needs of the plaintiff at the time it's created. But what happens if the installment arrangement no longer works for the individual? If you need cash for a large purchase or other expenses, consider selling your structured settlement. Many companies can purchase all or part of your remaining periodic settlement payments for one lump sum. This can boost your cash flow by providing funds you can use immediately to buy a home, pay college tuition, invest in a business or pay off debt.
If you're considering cashing out your structured settlement, contact your attorney first. Depending on the state you live in, you may have to go to court to get approval for the buyout. About two thirds of states have laws that limit the sale of structured settlements, according to the NSSTA. Tax-free structured settlements are also subject to federal restrictions on their sale to a third party, and some insurance companies won't assign or transfer annuities to third parties.
When selling your structure settlement, check with multiple companies to make sure that you get the highest payoff. Also, be sure the company buying your settlement is reputable and well-established. And keep in mind that if the deal sounds too good to be true, it probably is.

Effective Organization Structure Acts As Life Blood of Business

An organization structure is the way inwhich the tasks and subtasks required to implement a strategy are arranged. The diagrammatical representation of structure could be an organization chart but a chart shows only the 'skeleton'. The 'flesh and blood' that brings to life an organization is the several mechanisms that support the structure. All these cannot be depicted on a chart. But a strategist has to grapple with the complexities of creating the structure, making it work, redesigning when required, and implementing changes that will keep the structure relevant to the needs of the strategies that have to be implemented. Successful strategy formulation does not guarantee successful strategy implementation. Varies among different types & sizes of organizations Organization Structure Organizational structure & the controls that are a part of it affect firm's performance. When the firm's strategy is not matched with the most appropriate structure & controls, performance declines. Specifies the firm's formal reporting relationships, procedures, controls & authority, and decision-making process. Influences how managers work & the decisions resulting from that work. Specifies the work to be done & how to do it given the firm's strategy or strategies. Provides the stability a firm needs to successfully implement its strategies & maintain it's competitive advantages.
Structural Stability: Provides the capacity the firm requires to consistently and Predictably manage its daily work routines. Structural Flexibility: Provides the opportunity to explore competitive possibilities & allocate resources to activities that will shape the competitive advantages of the firm that it will need to be successful in the future.
Structure & Strategy
o Structure dictates how objectives & policies will be established.
o Structure dictates how resources will be allocated.
Matching Structure w/ Strategy Changes in strategy = Changes in structure Basic Forms of Structure
Mainly categorized in five types:
1. Entrepreneurial Structure
2. Functional Structure
3. Divisional Structure
4. Strategic Business Unit Structure (SBU)
5. Matrix Structure
1. Entrepreneurial Structure
The most elementary form of structure and is appropriate for an organization that is owned and managed by one person. A small-scale industrial unit, a small proprietary concern, or a mini-service outlet may exhibit the characteristics of organizations, which are based on an entrepreneurial structure.
Advantages of Entrepreneurial Structure
o Quick decision-making, as power is centralized.
o Timely response to environmental changes
Disadvantages of Entrepreneurial Structure
o Excessive reliance on the owner-manager and so proves to be demanding for the owner-manager
o May divert the attention of owner-manager to day-to-day operational matters and ignore strategic decision
o Increasingly inadequate for future requirements if volume of business expands
2. Functional Structure
As the volume of business expands, the entrepreneurial structure outlives its useful­ness. The need arises for specialized skills and delegation of authority to managers who can look after different functional areas. The functional structure seeks to distribute decision-making and operational authority along functional lines. Most widely used as simple and least expensive.
Advantages of functional structure
o Efficient distribution of work through specialization.
o Delegation of day-to-day operational functions
o Providing time for the top management to focus on strategic decisions
Disadvantages of functional structure
o Creates difficulty in coordination among different functional areas
o Creates specialists, which results in narrow specialization, often at the cost of the overall benefit of the organization
o Leads to functional, and line and staff conflicts
o Minimizes career development opportunities
o Poor delegation of authority, inadequate planning for products and markets
3. Divisional Structure
The structural needs of expansion and growth are satisfied by the functional structure but only up to a limit. There comes a time in the life of organizations when growth and increasing complexity in term of geographic expansion, market segmentation and diversification make the functional structure in adequate. Second most common type of structure can be organized by:
- Geographic area
- Product or service
- Customer
- Process
o Advantages
- Clear accountability
- Higher employee morale
- Creates career development opportunities for managers
- Allows local control of situations
- Leads to a competitive climate within an organization
- Allows new businesses and products to be added easily
o Disadvantages
- Can be costly to set up
- Each division requires functional specialists
- Duplication of staff services, facilities, and personnel
- Managers must be well qualified
- Requires an elaborate, headquarters-driven control system
- Competition between divisions may become so intense that it is dysfunctional
4. The Strategic Business Unit (SBU)
Any part of a business organization, which is treated separately for strategic management purposes. When organizations face difficulty in managing divisional operations due to an increasing diversity, size, and number of divisions, it becomes difficult for the top management to exercise strategic control. Here, the concept of an SBU is helpful in creating an SBU-organizational structure. In multidivisional organizations, an SBU structure can greatly facilitate strategy-implementation efforts.
Advantages of Strategic Business Unit (SBU)
º Establishes coordination between divisions having common strategic interests.
º Facilitates strategic management and control of large, diverse organizations.
º Fixes accountability at the level of distinct business units.
Disadvantages of Strategic Business Unit (SBU)
º There are too many different SBUs to handle effectively in a large, diverse organisation.
º Difficulty in assigning responsibility and defining autonomy for SBU heads.
º Addition of another layer of management between corporate and divisional management.
5. The Matrix Structure
Most complex of all designs - requires both vertical and horizontal flows of authority and communication. In large organization, there is often a need to work on major products or project each of which is strategically significant.
Advantages of The Matrix Structure
- Project objectives are clear
- Many channels of communication
- Workers can see visible results of their work
- Shutting down a project can be accomplished relatively easily
- Facilitates the use of specialized personnel, equipment, and facilities
Disadvantages of The Matrix Structure
- Can result in higher overhead
- Dual lines of budget authority
- Dual sources of reward and punishment
- Shared authority
- Dual reporting channels
- Need for an extensive and effective communication system
º All the structure has their own advantages and disadvantages.
º It is task of strategists to choose the type of structure that would suite their strategies best.
º We usually conceive of organization structure as a chart consisting of boxes in which the names of position or designations of personnel (and sometimes the name of the person occupying the position) are written in a hierarchical order along with the depiction of the relationship that exists between various positions. To a strategist, an organization structure is not only a chart but much more.

J. Chem. Phys.

First principles nuclear magnetic resonance signatures of graphene oxide

Ning Lu, Ying Huang , Hai-bei Li Zhenyu Li, and Jinlong Yang

Nuclear magnetic resonance (NMR) has been widely used in graphene oxide (GO) structure studies. However, the detailed relationship between its spectroscopic features and the GO structural configuration remains elusive. Based on first principles ¹³C chemical shift calculations using the gauge including projector augmented waves method, we provide a reliable spectrum-structure connection. The ¹³C chemical shift in GO is found to be very sensitive to the atomic environment, even for the same type of oxidation groups. Factors determining the chemical shifts of epoxy and hydroxy groups have been discussed. GO structures previously reported in the literature have been checked from the NMR point of view. The energetically favorable hydroxy chain structure is not expected to be widely existed in real GO samples according to our NMR simulations. The epoxy pair species we proposed previously is also supported by chemical shift calculations.

Determination of the antisymmetric part of the chemical shift anisotropy tensor via spin relaxation in nuclear magnetic resonance

Raphael Paquin, Philippe Pelupessy, Luminita Duma, Christel Gervais, and Geoffrey Bodenhausen

Relaxation processes induced by the antisymmetric part of the chemical shift anisotropy tensor (henceforth called anti-CSA) are usually neglected in NMR relaxation studies. It is shown here that anti-CSA components contribute to longitudinal relaxation rates of the indole ¹⁵N nucleus in tryptophan in solution at different magnetic fields and temperatures. To determine the parameters of several models for rotational diffusion and internal dynamics, we measured the longitudinal relaxation rates R₁ = 1/T₁ of ¹⁵N, the ¹⁵N–¹H dipole-dipole (DD) cross-relaxation rates (Overhauser effects), and the cross-correlated CSA/DD relaxation rates involving the second-rank symmetric part of the CSA tensor of ¹⁵N at four magnetic fields B₀ = 9.4, 14.1, 18.8, and 22.3 T (400, 600, 800, and 950 MHz for protons) over a temperature range of 270<T<310>. A good agreement between experimental and theoretical rates can only be obtained if the CSA tensor is assumed to comprise first-rank antisymmetric (anti-CSA) components. The magnitude of the hitherto neglected antisymmetric components is of the order of 10% of the CSA.

Noninvasive bipolar double-pulsed-field-gradient NMR reveals signatures for pore size and shape in polydisperse, randomly oriented, inhomogeneous porous media

Noam Shemesh, Evren Ozarslan, Tal Adiri, Peter J. Basser, and Yoram Cohen

Noninvasive characterization of pore size and shape in opaque porous media is a formidable challenge. NMR diffusion-diffraction patterns were found to be exceptionally useful for obtaining such morphological features, but only when pores are monodisperse and coherently placed. When locally anisotropic pores are randomly oriented, conventional diffusion NMR methods fail. Here, we present a simple, direct, and general approach to obtain both compartment size and shape even in such settings and even when pores are characterized by internal field gradients. Using controlled porous media, we show that the bipolar-double-pulsed-field-gradient (bp-d-PFG) methodology yields diffusion-diffraction patterns from which pore size can be directly obtained. Moreover, we show that pore shape, which cannot be obtained by conventional methods, can be directly inferred from the modulation of the signal in angular bp-d-PFG experiments. This new methodology significantly broadens the types of porous media that can be studied using noninvasive diffusion-diffraction NMR.

Analyzing molecular static linear response properties with perturbed localized orbitals

Jochen Autschbach and Harry F. King

Perturbed localized molecular orbitals (LMOs), correct to first order in an applied static perturbation and consistent with a chosen localization functional, are calculated using analytic derivative techniques. The formalism is outlined for a general static perturbation and variational localization functionals. Iterative and (formally) single-step approaches are compared. The implementation employs an iterative sequence of 2×2 orbital rotations. The procedure is verified by calculations of molecular electric-field perturbations. Boys LMO contributions to the electronic static polarizability and the electric-field perturbation of the 〈r²〉 expectation value are calculated and analyzed for ethene, ethyne, and fluoroethene (H₂CCHF). For ethene, a comparison is made with results from a Pipek–Mezey localization. The calculations show that a chemically intuitive decomposition of the calculated properties is possible with the help of the LMO contributions and that the polarizability contributions in similar molecules are approximately transferable.

Trading sensitivity for information: CarrPurcellMeiboomGill acquisition in solid-state NMR

Krishna K. Dey, Jason T. Ash, Nicole M. Trease, and Philip J. Grandinetti

The Carr–Purcell–Meiboom–Gill (CPMG) experiment has gained popularity in solid-state NMR as a method for enhancing sensitivity for anisotropically broadened spectra of both spin 1/2 and half integer quadrupolar nuclei. Most commonly, the train of CPMG echoes is Fourier transformed directly, which causes the NMR powder pattern to break up into a series of sidebands, sometimes called “spikelets.” Larger sensitivity enhancements are observed as the delay between the π pulses is shortened. As the duration between the π pulses is shortened, however, the echoes become truncated and information about the nuclear spin interactions is lost. We explored the relationship between enhanced sensitivity and loss of information as a function of the product Ω 2τ, where Ω is the span of the anisotropic lineshape and 2τ is the π pulse spacing. For a lineshape dominated by the nuclear shielding anisotropy, we found that the minimum uncertainty in the tensor values is obtained using Ω 2τ values in the range Ω 2τ ≈ 12−1+6 and Ω 2τ ≈ 9−3+3 for η_s = 0 and η_s = 1, respectively. For an anisotropic second-order quadrupolar central transition lineshape under magic-angle spinning (MAS), the optimum range of Ω 2τ ≈ 9−2+3 was found. Additionally, we show how the Two-dimensional One Pulse (TOP) like processing approach can be used to eliminate the cumbersome sideband pattern lineshape and recover a more familiar lineshape that is easily analyzed with conventional lineshape simulation algorithms

Optimized basis sets for the calculation of indirect nuclear spin-spin coupling constants involving the atoms B, Al, Si, P, and Cl

Patricio F. Provasi and Stephan P. A. Sauer

The aug-cc-pVTZ-J series of basis sets for indirect nuclear spin-spin coupling constants has been extended to the atoms B, Al, Si, P, and Cl. The basis sets were obtained according to the scheme previously described by Provasi et al. [J. Chem. Phys. 115, 1324 (2001)] . First, the completely uncontracted correlation consistent aug-cc-pVTZ basis sets were extended with four tight s and three tight d functions. Second, the s and p basis functions were contracted with the molecular orbital coefficients of self-consistent-field calculations performed with the uncontracted basis sets on the simplest hydrides of each atom. As a first illustration, we have calculated the one-bond indirect spin-spin coupling constants in BH4−, BF, AlH, AlF, SiH₄, SiF₄, PH₃, PF₃, H₂S, SF₆, HCl, and ClF at the level of density functional theory using the Becke three parameter Lee–Yang–Parr and the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes.

Recoupling of native homonuclear dipolar couplings in magic-angle-spinning solid-state NMR by the double-oscillating field technique

Lasse Arnt Straaso and Niels Chr. Nielsen

A new solid-state NMR method, the double-oscillating field technique (DUO), that under magic-angle-spinning conditions produces an effective Hamiltonian proportional to the native high-field homonuclear dipole-dipole coupling operator is presented. The method exploits one part of the radio frequency (rf) field to recouple the dipolar coupling interaction with a relatively high scaling factor and to eliminate offset effects over a reasonable bandwidth while in the recoupling frame, the other part gives rise to a sufficiently large longitudinal component of the residual rf field that averages nonsecular terms and in addition ensures stability toward rf inhomogeneity and rf miscalibration. The capability of the DUO experiment to mediate transfer of polarization is described theoretically and compared numerically and experimentally with finite pulse rf driven recoupling and experimentally with dipolar-assisted rotational resonance. Two-dimensional recoupling experiments were performed on antiparallel amyloid fibrils of the decapeptide SNNFGAILSS with the FGAIL fragment uniformly labeled with ¹³C and ¹⁵N.

J. Am. Chem. Soc., 2010, 132 (28), pp 9561–9563

Rapid Acquisition of Multidimensional Solid-State NMR Spectra of Proteins Facilitated by Covalently Bound Paramagnetic Tags
Philippe S. Nadaud, Jonathan J. Helmus, Ishita Sengupta and Christopher P. Jaroniec

We describe a condensed data collection approach that facilitates rapid acquisition of multidimensional magic-angle spinning solid-state nuclear magnetic resonance (SSNMR) spectra of proteins by combining rapid sample spinning, optimized low-power radio frequency pulse schemes and covalently attached paramagnetic tags to enhance protein 1H spin−lattice relaxation. Using EDTA-Cu2+-modified K28C and N8C mutants of the B1 immunoglobulin binding domain of protein G as models, we demonstrate that high resolution and sensitivity 2D and 3D SSNMR chemical shift correlation spectra can be recorded in as little as several minutes and several hours, respectively, for samples containing 0.1−0.2 μmol of 13C,15N- or 2H,13C,15N-labeled protein. This mode of data acquisition is naturally suited toward the structural SSNMR studies of paramagnetic proteins, for which the typical 1H longitudinal relaxation time constants are inherently a factor of at least 3−4 lower relative to their diamagnetic counterparts. To illustrate this, we demonstrate the rapid site-specific determination of backbone amide 15N longitudinal paramagnetic relaxation enhancements using a pseudo-3D SSNMR experiment based on 15N−13C correlation spectroscopy, and we show that such measurements yield valuable long-range 15N−Cu2+ distance restraints which report on the three-dimensional protein fold.



J. Am. Chem. Soc., 2010, 132 (29), pp 9952–9953
Validation of a Lanthanide Tag for the Analysis of Protein Dynamics by Paramagnetic NMR Spectroscopy
Mathias A. S. Hass, Peter H. J. Keizers, Anneloes Blok, Yoshitaka Hiruma and Marcellus Ubbink


Paramagnetic lanthanide tags potentially can enhance the effects of microsecond to millisecond dynamics in proteins on NMR signals and provide structural information on lowly populated states encoded in the pseudocontact shifts. We have investigated the microsecond to millisecond mobility of a two-point attached lanthanide tag, CLaNP-5, using paramagnetic 1H CPMG relaxation dispersion methods. CLaNP-5 loaded with Lu3+, Yb3+, or Tm3+ was attached to three sites on the surface of two proteins, pseudoazurin and cytochrome c. The paramagnetic center causes large relaxation dispersion effects for two attachment sites, suggesting that local dynamics of the protein at the attachment site causes mobility of the paramagnetic center. At one site the relaxation dispersions are small and limited to the immediate environment of the tag. It is concluded that paramagnetic relaxation dispersion could represent a sensitive method to probe protein dynamics. However, the selection of a rigid attachment site is of critical importance.


J. Am. Chem. Soc., 2010, 132 (29), pp 9956–9957
Solid-State 13C NMR Assignment of Carbon Resonances on Metallic and Semiconducting Single-Walled Carbon Nanotubes
Chaiwat Engtrakul*†, Mark F. Davis†, Kevin Mistry†, Brian A. Larsen†, Anne C. Dillon†, Michael J. Heben‡ and Jeffrey L. Blackburn*†


Solid-state 13C NMR spectroscopy was used to investigate the chemical shift of nanotube carbons on m- and s-SWNTs (metallic and semiconducting single-walled nanotubes) for samples with widely varying s-SWNT content, including samples highly enriched with nearly 100% m- and s-SWNTs. High-resolution 13C NMR was found to be a sensitive probe for m- and s-SWNTs in mixed SWNT samples with diameters of 1.3 nm. The two highly enriched m- and s-SWNT samples clearly exhibited features for m- and s-SNWT 13C nuclei (123 and 122 ppm, respectively) and were successfully fit with a single Gaussian, while five mixed samples required two Gaussians for a satisfactory fit.


J. Am. Chem. Soc., 2010, 132 (29), pp 9979–9981
Probing Slow Protein Dynamics by Adiabatic R1ρ and R2ρ NMR Experiments

Silvia Mangia, Nathaniel J. Traaseth, Gianluigi Veglia, Michael Garwood‡ and Shalom Michaeli

Slow μs/ms dynamics involved in protein folding, binding, catalysis, and allostery are currently detected using NMR dispersion experiments such as CPMG (Carr−Purcell−Meiboom−Gill) or spin-lock R1ρ. In these methods, protein dynamics are obtained by analyzing relaxation dispersion curves obtained from either changing the time spacing between 180° pulses or by changing the effective spin-locking field strength. In this Communication, we introduce a new method to induce a dispersion of relaxation rates. Our approach relies on altering the shape of the adiabatic full passage pulse and is conceptually different from existing approaches. By changing the nature of the adiabatic radiofrequency irradiation, we are able to obtain rotating frame R1ρ and R2ρ dispersion curves that are sensitive to slow μs/ms protein dynamics (demonstrated with ubiquitin). The strengths of this method are to (a) extend the dynamic range of the relaxation dispersion analysis, (b) avoid the need for multiple magnetic field strengths to extract dynamic parameters, (c) measure accurate relaxation rates that are independent of frequency offset, and (d) reduce the stress to NMR hardware (e.g., cryoprobes).

J Phys Chem A

Triple-Decker Sandwiches and Related Compounds of the First-Row Transition Metals Containing Cyclopentadienyl and Benzene Rings

Haibo Liu, Qian-shu Li, Yaoming Xie, R. Bruce King and Henry F. Schaefer

J. Phys. Chem. A, Article ASAP
DOI: 10.1021/jp104689r
Publication Date (Web): July 21, 2010

The triple-decker sandwich compound trans-Cp2V2(η6:η6-μ-C6H6) has been synthesized, as well as “slipped” sandwich compounds of the type trans-Cp2Co2(η4:η4-μ-arene) and the cis-Cp2Fe2(η4:η4-μ-C6R6) derivatives with an Fe−Fe bond (Cp = η5-cyclopentadienyl). Theoretical studies show that the symmetrical triple-decker sandwich structures trans-Cp2M2(η6:η6-μ-C6H6) are the global minima for M = Ti, V, and Mn but lie 10 kcal/mol above the global minimum for M = Cr. The nonbonding M···M distances and spin states in these triple decker sandwich compounds can be related to the occupancies of the frontier bonding molecular orbitals. The global minimum for the chromium derivative is a singlet spin state cis-Cp2Cr2(η4:η4-μ-C6H6) structure with a very short CrCr distance of 2.06 Å, suggesting a formal quadruple bond. A triplet state cis-Cp2Cr2(η4:η4-μ-C6H6) structure with a predicted Cr≡Cr distance of 2.26 Å lies only 3 kcal/mol above this global minimum. For the later transition metals the global minima are predicted to be cis-Cp2M2(η6:η6-μ-C6H6) structures with a metal−metal bond, rather than triple decker sandwiches. These include singlet cis-Cp2Fe2(η4:η4-μ-C6H6) with a predicted Fe═Fe double bond distance of 2.43 Å, singlet cis-Cp2Co2(η3:η3-μ-C6H6) with a predicted Co—Co single bond distance of 2.59 Å, and triplet cis-Cp2Ni2(η3:η3-μ-C6H6) with a predicted Ni—Ni distance of 2.71 Å.

J. Phys. Chem. C, vol.114, Issue 29

Molecular Modeling, Multinuclear NMR, and Diffraction Studies in the Templated Synthesis and Characterization of the Aluminophosphate Molecular Sieve STA-2

Maria Castro†, Valerie R. Seymour†, Diego Carnevale†, John M. Griffin†, Sharon E. Ashbrook*†, Paul A. Wright*†, David C. Apperley‡, Julia E. Parker§, Stephen P. Thompson§, Antoine Fecant and Nicolas Bats

J. Phys. Chem. C, 2010, 114 (29), pp 12698–12710
DOI: 10.1021/jp104120y
Copyright © 2010 American Chemical Society

Abstract: Molecular modeling has been used to assist in the design of a new structure directing agent (SDA) for the synthesis of the AlPO4 form of STA-2, bis-diazabicyclooctane-butane (BDAB). This is incorporated as a divalent cation within the large cages of STA-2, as determined via a combination of solid-state 13C and 15N MAS NMR, supported by 14N and 1H-15N HMQC solution NMR and density functional calculations. As-prepared AlPO4 STA-2 containing cationic SDA molecules achieves neutrality by the inclusion of hydroxide ions bridging between 5-fold coordinated framework Al atoms. Synchrotron X-ray powder diffraction data of the dehydrated as-prepared form indicates triclinic symmetry (Al12P12O48(OH)2·BDAB, P1, a = 12.3821(2) Å, b = 12.3795(2) Å, c = 12.3797(3) Å, α = 63.3585(8)°, β = 63.4830(7)°, γ = 63.4218(7)°) with the distortion from rhombohedral R symmetry resulting from the partial order of hydroxide ions in bridging Al−OH−Al sites within cancrinite cages. Upon calcination in oxygen, the organic SDA is removed, leaving AlPO4 STA-2 with a pore volume of 0.22 cm3 g−1 (R, Al36P36O144, a = 12.9270(2) Å, c = 30.7976(4) Å). Dehydrated calcined AlPO4 STA-2 has two crystallographically distinct P and Al sites: 31P MAS NMR resolves the two distinct P sites, and although 27Al MAS NMR only partially resolves the two Al sites, they are separated by MQMAS. Furthermore, 2D 27Al → 31P MQ-J-HETCOR correlation spectroscopy confirms that each framework Al is linked to the two different P sites via Al−O−P connections in a 3:1 ratio (and vice versa for P linked to different Al). The 27Al and 31P resonances are assigned to the crystallographic Al and P sites by calculation of the NMR parameters using the CASTEP DFT program for an energy-minimized AlPO4(SAT) framework.



Propane Aromatization on Zn-Modified Zeolite BEA Studied by Solid-State NMR in Situ

Anton A. Gabrienko†, Sergei S. Arzumanov†, Dieter Freude‡ and Alexander G. Stepanov*†
J. Phys. Chem. C, 2010, 114 (29), pp 12681–12688
DOI: 10.1021/jp103580f
Copyright © 2010 American Chemical Society

Abstract:The conversion of propane (propane-1-13C and propane-2-13C) on Zn/H-BEA zeolite at 520−620 K has been studied by 1H and 13C (CP) MAS NMR. Propene adsorption complex with zinc sites (π-complex) and σ-allylzinc species as intermediates have been identified in the course of propane conversion to aromatics. The mechanism leading to the formation of methane and ethane, which are constituents of an undesirable route in propane conversion, has been examined by kinetic modeling of the expected reaction network based on in situ 1H MAS NMR kinetic measurements of the reaction performance. The pathways for propane aromatization and hydrogenolysis have been proposed. Hydrogenolysis of propane has been concluded to occur with the involvement of both Brønsted acid sites and Zn sites.



13C Chemical Shift of Adsorbed Acetone for Measuring the Acid Strength of Solid Acids: A Theoretical Calculation Study

Hanjun Fang†‡, Anmin Zheng*†, Yueying Chu†‡ and Feng Deng*†
J. Phys. Chem. C, 2010, 114 (29), pp 12711–12718
DOI: 10.1021/jp1044749
Copyright © 2010 American Chemical Society

Abstract: Adsorption of basic probe molecules is one of the widely used methods to characterize the acid strength of solid acids. In this contribution, the adsorptions of acetone on various Brønsted and Lewis acid sites (from weak acid to superacid) are theoretically studied, in order to elucidate the quantitative relationships between 13C chemical shifts of acetone and intrinsic acid strength of solid acids. The Brønsted acid sites are represented by a series of 8T zeolite models with varying terminal Si−H bond lengths, and the different extents of acidic proton transfer from these acid sites to acetone are revealed explicitly. We found that three adsorption conformations (hydrogen-bonded, proton-shared, and ion-pair) exist for acetone, and concurrently, a correlation of three-broken lines is obtained for the 13C chemical shift of acetone versus the deprotonation energy (DPE). The correlation can be used as a scale for quantitatively measuring the Brønsted acid strength of solid acids. A threshold of 245 ppm is determined for superacidity, in good agreement with the experimental value (244 ppm). The Lewis acid sites are modeled by tricoordinate framework aluminum species and various extra-framework aluminum cations or neutral species such as Al3+, AlO+, AlOH2+, Al(OH)2+, Al(OH)3, and AlOOH. We found that acetone is coordinately adsorbed on the aluminum atoms of Lewis acid sites and that the 13C chemical shift of acetone is almost linear to the lowest unoccupied molecular orbital (LUMO) energy of the acid sites.

J. Phys. Chem C. v. 114, issue 28

45Sc Spectroscopy of Solids: Interpretation of Quadrupole Interaction Parameters and Chemical Shifts



Mara D. Alba*†, Pablo Chain†, Pierre Florian‡ and Dominique Massiot‡



J. Phys. Chem. C, 2010, 114 (28), pp 12125–12132

Publication Date (Web): June 28, 2010



Abstract: The aims of the present study is to describe for the first time the 45Sc MAS NMR spectra of X2-Sc2SiO5 and C-Sc2Si2O7, to combine the spectroscopic information with the structures published from diffraction data, and to propose a rational interpretation of the chemical shifts and quadrupolar parameters. For that purposed, we have correlated the experimental quadrupole coupling parameters of 45Sc determined for a number of scandium compounds to those found by a simple electrostatic calculation and we have found that the isotropic chemical shift of the 45Sc is linearly correlated to the shift parameter, calculated by bond-valence theory. We also show that a simple point charge calculation can approximate the electric field gradient to a sufficiently good approximation that it provides a valuable mean to assign the NMR spectra.





Nuclear Magnetic Resonance Study of Reorientational Motion in α-Mg(BH4)2

Alexander V. Skripov*†, Alexei V. Soloninin†, Olga A. Babanova†, Hans Hagemann‡ and Yaroslav Filinchuk§

J. Phys. Chem. C, 2010, 114 (28), pp 12370–12374

Copyright © 2010 American Chemical Society



Abstract: To study the reorientational motion of BH4 groups in the low-temperature (α) phase of Mg(BH4)2, we have performed nuclear magnetic resonance (NMR) measurements of the 1H and 11B spin−lattice relaxation rates in this compound over wide ranges of temperature (82−443 K) and resonance frequency (14−90 MHz for 1H and 14−28 MHz for 11B). It is found that the thermally activated reorientational motion in α-Mg(BH4)2 is characterized by a coexistence of at least three jump processes with strongly differing activation energies. Taking into account the anisotropy of the local environment of BH4 groups in α-Mg(BH4)2, these jump processes can be attributed to different types of reorientation. The nearly linear coordination of BH4 groups by two Mg atoms suggests that the fastest jump process corresponds to the rotation around the 2-fold axis connecting B and two Mg atoms, whereas the slowest process is associated with the rotation around two other 2-fold axes perpendicular to the Mg−B−Mg line.

Journal of Magnetic Resonance ASAP

A bit of shameless self-promotion:

Journal of Magnetic Resonance
Article in Press
doi:10.1016/j.jmr.2010.05.018

The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra
Aaron J. Rossinia, Hiyam Hamaeda and Robert W. Schurko, a,

Abstract:The acquisition of nuclear quadrupole resonance (NQR) spectra with wideband uniform rate and smooth truncation (WURST) pulses is investigated. 75As and 35Cl NQR spectra acquired with the WURST echo sequence are compared to those acquired with standard Hahn-echo sequences and echo sequences which employ composite refocusing pulses. The utility of WURST pulses for locating NQR resonances of unknown frequency is investigated by monitoring the integrated intensity and signal to noise of 35Cl and 75As NQR spectra acquired with transmitter offsets of several hundreds kilohertz from the resonance frequencies. The WURST echo sequence is demonstrated to possess superior excitation bandwidths in comparison to the pulse sequences which employ conventional monochromatic rectangular pulses. The superior excitation bandwidths of the WURST pulses allows for differences in the characteristic impedance of the receiving and excitation circuits of the spectrometer to be detected. Impedance mismatches have previously been reported by Marion and Desvaux [D.J.Y. Marion, H. Desvaux, J. Magn. Reson. (2008) 193(1) 153–157] and Muller et al. [M. Nausner, J. Schlagnitweit, V. Smrecki, X. Yang, A. Jerschow, N. Muller, J. Magn. Reson. (2009) 198(1) 73–79]. In this regard, WURST pulse sequences may afford an efficient new method for experimentally detecting impedance mismatches between receiving and excitation circuits, allowing for the optimization of solids and solution NMR and NQR spectrometer systems. The use of the Carr–Purcell Meiboom–Gill (CPMG) pulse sequence for signal enhancement of NQR spectra acquired with WURST pulses and conventional pulses is also investigated. Finally, the utility of WURST pulses for the acquisition of wideline NQR spectra is demonstrated by acquiring part of the 63/65Cu NQR spectrum of CuCN.

Magn. Reson. Chem. - July 2010

New perspectives in the PAW/GIPAW approach: JP-O-Si coupling constants, antisymmetric parts of shift tensors and NQR predictions

from Magnetic Resonance in Chemistry by Christian Bonhomme, Christel Gervais, Cristina Coelho, Frédérique Pourpoint, Thierry Azaïs, Laure Bonhomme-Coury, Florence Babonneau, Guy Jacob, Maude Ferrari, Daniel Canet, Jonathan R. Yates, Chris J. Pickard, Siân A. Joyce, Francesco Mauri, Dominique Massiot

In 2001, Pickard and Mauri implemented the gauge including projected augmented wave (GIPAW) protocol for first-principles calculations of NMR parameters using periodic boundary conditions (chemical shift anisotropy and electric field gradient tensors). In this paper, three potentially interesting perspectives in connection with PAW/GIPAW in solid-state NMR and pure nuclear quadrupole resonance (NQR) are presented: (i) the calculation of J coupling tensors in inorganic solids; (ii) the calculation of the antisymmetric part of chemical shift tensors and (iii) the prediction of 14N and 35Cl pure NQR resonances including dynamics. We believe that these topics should open new insights in the combination of GIPAW, NMR/NQR crystallography, temperature effects and dynamics. Points (i), (ii) and (iii) will be illustrated by selected examples: (i) chemical shift tensors and heteronuclear 2JP[bond]O[bond]Si coupling constants in the case of silicophosphates and calcium phosphates [Si5O(PO4)6, SiP2O7 polymorphs and [alpha]-Ca(PO3)2]; (ii) antisymmetric chemical shift tensors in cyclopropene derivatives, C3X4 (X = H, Cl, F) and (iii) 14N and 35Cl NQR predictions in the case of RDX (C3H6N6O6), [beta]-HMX (C4H8N8O8), [alpha]-NTO (C2H2N4O3) and AlOPCl6. RDX, [beta]-HMX and [alpha]-NTO are explosive compounds.

Received: 31 March 2010; Revised: 17 May 2010; Accepted: 20 May 2010
Digital Object Identifier (DOI)
10.1002/mrc.2635


Computation and NMR crystallography of terbutaline sulfate
from Magnetic Resonance in Chemistry by Robin K. Harris, Paul Hodgkinson, Vadim Zorin, Jean-Nicolas Dumez, Bénédicte Elena-Herrmann, Lyndon Emsley, Elodie Salager, Robin S. Stein

This article addresses, by means of computation and advanced experiments, one of the key challenges of NMR crystallography, namely the assignment of individual resonances to specific sites in a crystal structure. Moreover, it shows how NMR can be used for crystal structure validation. The case examined is form B of terbutaline sulfate. CPMAS 13C and fast MAS 1H spectra have been recorded and the peaks assigned as far as possible. Comparison of 13C chemical shifts computed using the CASTEP program (incorporating the Gauge Including Projector Augmented Wave principle) with those obtained experimentally enable the accuracy of the two distinct single-crystal evaluations of the structure to be compared and an error in one of these is located. The computations have substantially aided in the assignments of both 13C and 1H resonances, as has a series of two-dimensional (2D) spectra (HETCOR, DQ-CRAMPS and proton-proton spin diffusion). The 2D spectra have enabled many of the proton chemical shifts to be pinpointed. The relationships of the NMR shifts to the specific nuclear sites in the crystal structure have therefore been established for most 13C peaks and for some 1H signals. Emphasis is placed on the effects of hydrogen bonding on the proton chemical shifts.

Received: 26 March 2010; Revised: 20 May 2010; Accepted: 24 May 2010
Digital Object Identifier (DOI)
10.1002/mrc.2636


Prediction of NMR J-coupling in solids with the planewave pseudopotential approach
from Magnetic Resonance in Chemistry by Jonathan R. Yates
We review the calculation of NMR J-coupling in solid materials using the planewave pseudopotential formalism of Density Functional Theory. The methodology is briefly summarised and an account of recent applications is given. We discuss various aspects of the calculations which should be taken into account when comparing results with solid-state NMR experiments including anisotropy and orientation of the J tensors, the reduced coupling constant, and the relation between J and crystal structure. Copyright © 2010 John Wiley & Sons, Ltd.

Received: 20 April 2010; Revised: 2 June 2010; Accepted: 4 June 2010
Digital Object Identifier (DOI)
10.1002/mrc.2646


Comparing quantum-chemical calculation methods for structural investigation of zeolite crystal structures by solid-state NMR spectroscopy
from Magnetic Resonance in Chemistry by Darren H. Brouwer, Igor L. Moudrakovski, Richard J. Darton, Russell E. Morris

Combining quantum-chemical calculations and ultrahigh-field NMR measurements of 29Si chemical shielding (CS) tensors has provided a powerful approach for probing the fine details of zeolite crystal structures. In previous work, the quantum-chemical calculations have been performed on 'molecular fragments' extracted from the zeolite crystal structure using Hartree-Fock methods (as implemented in Gaussian). Using recently acquired ultrahigh-field 29Si NMR data for the pure silica zeolite ITQ-4, we report the results of calculations using recently developed quantum-chemical calculation methods for periodic crystalline solids (as implemented in CAmbridge Serial Total Energy Package (CASTEP) and compare these calculations to those calculated with Gaussian. Furthermore, in the context of NMR crystallography of zeolites, we report the completion of the NMR crystallography of the zeolite ITQ-4, which was previously solved from NMR data. We compare three options for the 'refinement' of zeolite crystal structures from 'NMR-solved' structures: (i) a simple target-distance based geometry optimization, (ii) refinement of atomic coordinates in which the differences between experimental and calculated 29Si CS tensors are minimized, and (iii) refinement of atomic coordinates to minimize the total energy of the lattice using CASTEP quantum-chemical calculations. All three refinement approaches give structures that are in remarkably good agreement with the single-crystal X-ray diffraction structure of ITQ-4.

Received: 31 March 2010; Revised: 27 May 2010; Accepted: 2 June 2010
Digital Object Identifier (DOI)
10.1002/mrc.2642

Prog. in NMR Spectrosc. - July 2010 - Floquet theory

Progress in Nuclear Magnetic Resonance Spectroscopy
doi:10.1016/j.pnmrs.2010.06.002
Floquet Theory in Solid-State Nuclear Magnetic Resonance
Michal Leskes, P.K. Madhu, Shimon Vega

Received 12 April 2010; accepted 11 June 2010. Available online 30 June 2010.

Keywords: Solid-state NMR; Floquet Theory; van Vleck transformation; Average Hamiltonian Theory

Journal Update

J. Am. Chem. Soc., 2010, 132 (16), pp 5538–5539

Breaking the T1 Constraint for Quantitative Measurement in Magic Angle Spinning Solid-State NMR Spectroscopy
Guangjin Hou, Shangwu Ding, Limin Zhang and Feng Deng

Quantitative solid-state NMR experimental schemes that break the conventional T1 constraint are described. The combination of broad-band homonuclear recoupling techniques and the conventional single pulse or cross-polarization (CP) schemes (referred as QUSP or QUCP) render the long T1 of low-? spins no longer a constraint for obtaining quantitative NMR spectra. During the mixing time when dipolar recoupling occurs, the nonuniformly CP enhanced or recovered spin magnetization is redistributed under the reintroduced homonuclear dipole-dipole interactions so that uniformly enhanced or recovered magnetization is achieved when the system reaches the quasi-equilibrium state. It is shown that quantitative NMR spectra can be obtained for the recycle delays substantially shorter than the conventionally required 5T1. In addition, the high efficiency gain can be achieved in QUSP and QUCP experiments with a relatively short recycle delay.


J. Am. Chem. Soc., 2010, 132 (16), pp 5546–5547

Detection of Transient Interchain Interactions in the Intrinsically Disordered Protein a-Synuclein by NMR Paramagnetic Relaxation Enhancement
Kuen-Phon Wu and Jean Baum


NMR paramagnetic relaxation enhancement experiments were applied to the intrinsically disordered protein a-synuclein, the primary protein in Parkinson's disease, to directly characterize transient intermolecular complexes at neutral and low pH. At neutral pH, we observed weak N- to C-terminal interchain contacts driven by electrostatic interactions, while at low pH, the C- to C-terminal interchain interactions are significantly stronger and driven by hydrophobic contacts. Characterization of these first interchain interactions will provide fundamental insight into the mechanism of amyloid formation.

J. Am. Chem. Soc., 2010, 132 (16), pp 5556–5557

Fibrillar vs Crystalline Full-Length ß-2-Microglobulin Studied by High-Resolution Solid-State NMR Spectroscopy
Emeline Barbet-Massin†, Stefano Ricagno‡§, Józef R. Lewandowski†, Sofia Giorgetti§, Vittorio Bellotti‡§, Martino Bolognesi, Lyndon Emsley† and Guido Pintacuda*†

Elucidating the fine structure of amyloid fibrils as well as understanding their processes of nucleation and growth remains a difficult yet essential challenge, directly linked to our current poor insight into protein misfolding and aggregation diseases. Here we consider ß-2-microglobulin (ß2m), the MHC-1 light chain component responsible for dialysis-related amyloidosis, which can give rise to amyloid fibrils in vitro under various experimental conditions, including low and neutral pH. We have used solid-state NMR to probe the structural features of fibrils formed by full-length ß2m (99 residues) at pH 2.5 and pH 7.4. A close comparison of 2D 13C-13C and 15N-13C correlation experiments performed on ß2m, in both the crystalline and fibrillar states, suggests that, in spite of structural changes affecting the protein loops linking the protein ß-strands, the protein chain retains a substantial share of its native secondary structure in the fibril assembly. Moreover, variations in the chemical shifts of the key Pro32 residue suggest the involvement of a cis-trans isomerization in the process of ß2m fibril formation. Lastly, the analogy of the spectra recorded on ß2m fibrils grown at different pH values hints at a conserved architecture of the amyloid species thus obtained.

J. Am. Chem. Soc., 2010, 132 (16), pp 5558–5559


Ultrafast MAS Solid-State NMR Permits Extensive 13C and 1H Detection in Paramagnetic Metalloproteins
Ivano Bertini, Lyndon Emsley§, Moreno Lelli, Claudio Luchinat, Jiafei Mao and Guido Pintacuda

We show here that by combining tailored approaches based on ultrafast (60 kHz) MAS on the CoII-replaced catalytic domain of matrix metalloproteinase 12 (CoMMP-12) we can observe and assign, in a highly paramagnetic protein in the solid state, 13C and even 1H resonances from the residues coordinating the metal center. In addition, by exploiting the enhanced relaxation caused by the paramagnetic center, and the low power irradiation enabled by the fast MAS, this can be achieved in remarkably short times and at very high field (21.2 T), with only less than 1 mg of sample. Furthermore, using the known crystal structure of the compound, we are able to distinguish and measure pseudocontact (PCS) contributions to the shifts up to the coordinating ligands and to unveil structural information.

J. Am. Chem. Soc., 2010, 132 (16), pp 5672–5676


NMR-Based Structural Modeling of Graphite Oxide Using Multidimensional 13C Solid-State NMR and ab Initio Chemical Shift Calculations
Leah B. Casabianca†, Medhat A. Shaibat†, Weiwei W. Cai‡, Sungjin Park‡, Richard Piner‡, Rodney S. Ruoff‡ and Yoshitaka Ishii†

Chemically modified graphenes and other graphite-based materials have attracted growing interest for their unique potential as lightweight electronic and structural nanomaterials. It is an important challenge to construct structural models of noncrystalline graphite-based materials on the basis of NMR or other spectroscopic data. To address this challenge, a solid-state NMR (SSNMR)-based structural modeling approach is presented on graphite oxide (GO), which is a prominent precursor and interesting benchmark system of modified graphene. An experimental 2D 13C double-quantum/single-quantum correlation SSNMR spectrum of 13C-labeled GO was compared with spectra simulated for different structural models using ab initio geometry optimization and chemical shift calculations. The results show that the spectral features of the GO sample are best reproduced by a geometry-optimized structural model that is based on the Lerf-Klinowski model (Lerf, A. et al. Phys. Chem. B 1998, 102, 4477); this model is composed of interconnected sp2, 1,2-epoxide, and COH carbons. This study also convincingly excludes the possibility of other previously proposed models, including the highly oxidized structures involving 1,3-epoxide carbons (Szabo, I. et al. Chem. Mater. 2006, 18, 2740). 13C chemical shift anisotropy (CSA) patterns measured by a 2D 13C CSA/isotropic shift correlation SSNMR were well reproduced by the chemical shift tensor obtained by the ab initio calculation for the former model. The approach presented here is likely to be applicable to other chemically modified graphenes and graphite-based systems.


J. Am. Chem. Soc., 2010, 132 (16), pp 5779–5788


Proton-Evolved Local-Field Solid-State NMR Studies of Cytochrome b5 Embedded in Bicelles, Revealing both Structural and Dynamical Information
Ronald Soong†, Pieter E. S. Smith†, Jiadi Xu†, Kazutoshi Yamamoto†, Sang-Choul Im‡, Lucy Waskell‡ and Ayyalusamy Ramamoorthy*†

Structural biology of membrane proteins has rapidly evolved into a new frontier of science. Although solving the structure of a membrane protein with atomic-level resolution is still a major challenge, separated local field (SLF) NMR spectroscopy has become an invaluable tool in obtaining structural images of membrane proteins under physiological conditions. Recent studies have demonstrated the use of rotating-frame SLF techniques to accurately measure strong heteronuclear dipolar couplings between directly bonded nuclei. However, in these experiments, all weak dipolar couplings are suppressed. On the other hand, weak heteronuclear dipolar couplings can be measured using laboratory-frame SLF experiments, but only at the expense of spectral resolution for strongly dipolar coupled spins. In the present study, we implemented two-dimensional proton-evolved local-field (2D PELF) pulse sequences using either composite zero cross-polarization (COMPOZER-CP) or windowless isotropic mixing (WIM) for magnetization transfer. These PELF sequences can be used for the measurement of a broad range of heteronuclear dipolar couplings, allowing for a complete mapping of protein dynamics in a lipid bilayer environment. Experimental results from magnetically aligned bicelles containing uniformly 15N-labeled cytochrome b5 are presented and theoretical analyses of the new PELF sequences are reported. Our results suggest that the PELF-based experimental approaches will have a profound impact on solid-state NMR spectroscopy of membrane proteins and other membrane-associated molecules in magnetically aligned bicelles.

J. Am. Chem. Soc., 2010, 132 (16), pp 5803–5811

Changes in Transmembrane Helix Alignment by Arginine Residues Revealed by Solid-State NMR Experiments and Coarse-Grained MD Simulations
Vitaly V. Vostrikov‡†, Benjamin A. Hall§†, Denise V. Greathouse‡, Roger E. Koeppe, II*‡ and Mark S. P. Sansom*§

Independent experimental and computational approaches show agreement concerning arginine/membrane interactions when a single arginine is introduced at selected positions within the membrane-spanning region of acetyl-GGALW5LALALAL12AL14ALALW19LAGA-ethanolamide, designated GWALP23. Peptide sequence isomers having Arg in position 12 or position 14 display markedly different behaviors, as deduced by both solid-state NMR experiments and coarse-grained molecular dynamics (CG-MD) simulations. With respect to the membrane normal of DOPC or DPPC lipid bilayer membranes, GWALP23-R14 shows one major state whose apparent average tilt is 10° greater than that of GWALP23. The presence of R14 furthermore induces bilayer thinning and peptide displacement to "lift" the charged guanidinium toward the bilayer surface. By contrast, GWALP23-R12 exhibits multiple states that are in slow exchange on the NMR time scale, with CG-MD simulations indicating two distinct positions with different screw rotation angles in the membrane, along with an increased tendency to exit the lipid bilayer.

Hiyam's Journal Update

J. Am. Chem. Soc., 2010, 132 (21), pp 7321–7337

Molecular Silicate and Aluminate Species in Anhydrous and Hydrated Cements
Aditya Rawal, Benjamin J. Smith†, George L. Athens, Christopher L. Edwards, Lawrence Roberts, Vijay Gupta and Bradley F. Chmelka


The compositions and molecular structures of anhydrous and hydrated cements are established by using advanced solid-state nuclear magnetic resonance (NMR) spectroscopy methods to distinguish among different molecular species and changes that occur as a result of cement hydration and setting. One- and two-dimensional (2D) solid-state 29Si and 27Al magic-angle spinning NMR methodologies, including T1-relaxation-time- and chemical-shift-anisotropy-filtered measurements and the use of very high magnetic fields (19 T), allow resonances from different silicate and aluminate moieties to be resolved and assigned in complicated spectra. Single-pulse 29Si and 27Al NMR spectra are correlated with X-ray fluorescence results to quantify the different crystalline and disordered silicate and aluminate species in anhydrous and hydrated cements. 2D 29Si{1H} and 27Al{1H}heteronuclear correlation NMR spectra of hydrated cements establish interactions between water and hydroxyl moieties with distinct 27Al and 29Si species. The use of a 29Si T1-filter allows anhydrous and hydrated silicate species associated with iron-containing components in the cements to be distinguished, showing that they segregate from calcium silicate and aluminate components during hydration. The different compositions of white Portland and gray oilwell cements are shown to have distinct molecular characteristics that are correlated with their hydration behaviors.


A Resonance Assignment Method for Oriented-Sample Solid-State NMR of Proteins
Robert W. Knox†, George J. Lu‡, Stanley J. Opella‡ and Alexander A. Nevzorov

J. Am. Chem. Soc., 2010, 132 (24), pp 8255–8257

A general sequential assignment strategy for uniformly 15N-labeled uniaxially aligned membrane proteins is proposed. Mismatched Hartmann−Hahn magnetization transfer is employed to establish proton-mediated correlations among the neighboring 15N backbone spins. Magnetically aligned Pf1 phage coat protein was used to illustrate the method. Exchanged and nonexchanged separated local field spectra were acquired and overlaid to distinguish the cross-peaks from the main peaks. Most of the original assignments from the literature were confirmed without selectively labeled samples. This method is applicable to proteins with arbitrary topology and will find use in assigning solid-state NMR spectra of oriented membrane proteins for their subsequent structure determination.



The Polar Phase of NaNbO3: A Combined Study by Powder Diffraction, Solid-State NMR, and First-Principles Calculations
Karen E. Johnston†, Chiu C. Tang‡, Julia E. Parker‡, Kevin S. Knight§, Philip Lightfoot*† and Sharon E. Ashbrook*†

J. Am. Chem. Soc., 2010, 132 (25), pp 8732–8746

A polar phase of NaNbO3 has been successfully synthesized using sol-gel techniques. Detailed characterization of this phase has been undertaken using high-resolution powder diffraction (X-ray and neutron) and 23Na multiple-quantum (MQ) MAS NMR, supported by second harmonic generation measurements and density functional theory calculations. Samples of NaNbO3 were also synthesized using conventional solid-state methods and were observed to routinely comprise of a mixture of two different polymorphs of NaNbO3, namely, the well-known orthorhombic phase (space group Pbcm) and the current polar phase, the relative quantities of which vary considerably depending upon precise reaction conditions. Our studies show that each of these two polymorphs of NaNbO3 contains two crystallographically distinct Na sites. This is consistent with assignment of the polar phase to the orthorhombic space group P21ma, although peak broadenings in the diffraction data suggest a subtle monoclinic distortion. Using carefully monitored molten salt techniques, it was possible to eradicate the polar polymorph and synthesize the pure Pbcm phase.


NMR Methods for Characterizing the Pore Structures and Hydrogen Storage Properties of Microporous Carbons
Robert J. Anderson†, Thomas P. McNicholas‡, Alfred Kleinhammes*†, Anmiao Wang‡, Jie Liu‡ and Yue Wu†

J. Am. Chem. Soc., 2010, 132 (25), pp 8618–8626

1H NMR spectroscopy is used to investigate a series of microporous activated carbons derived from a poly(ether ether ketone) (PEEK) precursor with varying amounts of burnoff (BO). In particular, properties relevant to hydrogen storage are evaluated such as pore structure, average pore size, uptake, and binding energy. High-pressure NMR with in situ H2 loading is employed with H2 pressure ranging from 100 Pa to 10 MPa. An N2-cooled cryostat allows for NMR isotherm measurements at both room temperature (290 K) and 100 K. Two distinct 1H NMR peaks appear in the spectra which represent the gaseous H2 in intergranular pores and the H2 residing in micropores. The chemical shift of the micropore peak is observed to evolve with changing pressure, the magnitude of this effect being correlated to the amount of BO and therefore the structure. This is attributed to the different pressure dependence of the amount of adsorbed and non-adsorbed molecules within micropores, which experience significantly different chemical shifts due to the strong distance dependence of the ring current effect. In pores with a critical diameter of 1.2 nm or less, no pressure dependence is observed because they are not wide enough to host
non-adsorbed molecules; this is the case for samples with less than 35% BO. The largest estimated pore size that can contribute to the micropore peak is estimated to be around 2.4 nm. The total H2 uptake associated with pores of this size or smaller is evaluated via a calibration of the isotherms, with the highest amount being observed at 59% BO. Two binding energies are present in the micropores, with the lower, more dominant one being on the order of 5 kJ mol−1 and the higher one ranging from 7 to 9 kJ mol−1.


Characterization of RNA Invasion by 19F NMR Spectroscopy
Anu Kiviniemi and Pasi Virta*

J. Am. Chem. Soc., 2010, 132 (25), pp 8560–8562

19F NMR spectroscopy offers an efficient tool for monitoring RNA invasion. The invasion of 2′-O-methyl oligoribonucleotides into a 19F-labeled HIV-1 TAR RNA model and the temperature-dependent behavior of the complexes obtained have been examined.

J. Phys. Chem. A

Solid-State NMR Spectra and Long, Intra-Dimer Bonding in the π-[TTF]22+ (TTF = Tetrathiafulvalene) Dication

Merrill D. Halling, Joshua D. Bell, Ronald J. Pugmire, David M. Grant* and Joel S. Miller

J. Phys. Chem. A, 2010, 114 (24), pp 6622–6629
DOI: 10.1021/jp910509f
Publication Date (Web): June 2, 2010

The 13C chemical-shift tensor principal values for TTF and π-[TTF]22+ (TTF = tetrathiafulvalene) dimer dications have been measured in order to better understand the electronic structure and long intradimer bonding of these TTF-based dimer structures. The structure of π-[TTF]22+ is abnormal due to its two C−C and four S−S ca. 3.4 Å intradimer separations, which is less than the sum of the sulfur van der Waals radii, and has a singlet 1A1g electronic ground state. This study of TTF and [TTF]22+ was conducted to determine how the NMR chemical-shift tensor principal values change as a function of electronic structure. This study also establishes a better understanding of the interactions that lead to spin-pairing of the monomeric radical units. The density functional theory (DFT) calculated nuclear shielding tensors are correlated with the experimentally determined principal chemical-shift values. The embedded ion method (EIM) was used to investigate the electrostatic lattice potential in [TTF]22+. These theoretical methods provide information on the tensor magnitudes and orientations of their tensor principal values with respect to the molecular frame. The experimental chemical-shift principal values agree with the calculated quantum mechanical chemical-shielding principal values, within typical errors commonly seen for this class of molecular system. Relatively weak Wiberg bond orders between the two [TTF]+ components of the dimer dication correlate with the long bonds linking the two [TTF]+ monomers and substantiate the claim that there is weak multicenter bonding present.
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Interpretation of Indirect Nuclear Spin−Spin Couplings in Isomers of Adenine: Novel Approach to Analyze Coupling Electron Deformation Density Using Localized Molecular Orbitals

Radek Marek*, Aneka Kstkov, Kateina Malikov, Jaromr Touek, Jaromr Marek, Michal Hocek, Olga L. Malkina* and Vladimir G. Malkin

J. Phys. Chem. A, 2010, 114 (24), pp 6689–6700
DOI: 10.1021/jp102186r
Publication Date (Web): June 2, 2010

Adenine, an essential building block of nucleic acids present in all living systems, can occur in several tautomeric forms. The phenomenon of tautomerism can be investigated by several experimental methods, including nuclear magnetic resonance. In this study, long-range 1H−13C and 1H−15N coupling constants for N-alkyl derivatives related to four tautomers of adenine are investigated in DMSO and DMF solutions. To investigate the structural dependence of the coupling constants and to understand how polarization propagates in the system, Fermi contact (FC) terms were calculated for the individual isomers and analyzed by using density functional theory (DFT), and the coupling pathways were visualized using real-space functions. The coupling electron deformation densities (CDD) of several 1H−X (X = 13C, 15N) pairs are evaluated and compared. In order to analyze the CDD in more detail, a new approach to break down the CDD into contributions from Boys or Pipek−Mezey localized molecular orbitals (LMOs) has been developed. A similar approach has been applied to split the value of the FC contribution to the J coupling into the LMO contributions. On the basis of chemical concepts, the contributions of σ-bonds, π-electrons, and lone pairs of electrons are discussed. The lone pair of electrons at the nitrogen atom contributes significantly to the 1H−C═15N coupling, whereas the 1H−C═N−13C coupling is affected in a somewhat different way. Surprisingly, the contribution of the intervening C═N bond to the FC term for 1H−C═15N coupling originates exclusively in σ-electrons, with a vanishingly small contribution calculated for the π-electrons of this fragment. This behavior is rationalized by introducing the concept of “hard and soft J elements” derived from the polarizability of the individual components.
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NMR Spectroscopic Parameters of Molecular Systems with Strong Hydrogen Bonds

Natalia Zarycz and Gustavo A. Aucar*

J. Phys. Chem. A, Article ASAP
DOI: 10.1021/jp1019334
Publication Date (Web): June 16, 2010

A series of closed H-bonded molecules that have (or not) delocalized bonds were studied. The dependence of both NMR spectroscopic parameters σ and J-couplings, and also the energy stability of such molecules with H-bond strength, were analyzed. The selected basic geometrical structure was that of malonaldehyde. From its full optimized geometry, the corresponding geometry of 3-OH propanal was obtained, fixing either the d(O−O) distance or a more extended local geometry and then optimizing the other part of the whole structure. Nitromalonaldehyde and nitromalonamide were also studied because they should have stronger H-bonds and their basic structure is also malonaldehyde. The last one also has electronic effects that may be varied by rotating the amino groups. By doing this it is possible to show that the effects on acidity of donors are more important than the equivalent effects on the basicity of acceptors. It is also shown that J-couplings that involve atoms close to the H-bond have important noncontact contributions that must be included in order to reproduce total J values. Noncontact contributions are more important than the Fermi contact (FC) one for J(O−O) in malonaldehyde. In nitromalonamide all three terms, FC, paramagnetic spin-orbital, and spin-dipolar are of the same order of magnitude when both amino groups are rotated. This does not happen for its planar configuration. Nuclear magnetic shielding of the hydrogen belonging to the H-bond is quite sensitive to it. The magnetic behavior of such hydrogen atom is modified when it is part of a closed H-bonded molecule. Then a relationship between the H-bond strength with the paramagnetic contributions of the shieldings of both atoms, C and O of the donor substructure, was obtained. We have found a cubic correlation between σp (C) of the C−O donor bond with σ (H) of the H-bonded hydrogen. It is observed that both the noncontact J-coupling contributions and shieldings on atoms belonging to the donor substructure, give a clear evidence about the presence of the resonance phenomenon in the model compounds that have been studied, malonaldehyde, nitromalonaldehyde, and nitromalonamide.
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Spin-State-Corrected Gaussian-Type Orbital Basis Sets

Marcel Swart*, Mireia Gell, Josep M. Luis and Miquel Sola

J. Phys. Chem. A, Article ASAP
DOI: 10.1021/jp102712z
Publication Date (Web): June 16, 2010

Recently, we reported that the basis set has a profound influence on the computed values for spin-state splittings [ J. Phys. Chem. A 2008, 112, 6384]. In particular, small Gaussian-type orbital (GTO) basis sets were shown to be unreliable for the prediction of them. Here, we report simple modifications of the small Pople-type Gaussian-type orbital basis sets (3-21G, 3-21G*, 6-31G, 6-31G*), which correct their faulty behavior for the spin-state energies. We have investigated the basis sets for a set of 13 first-row transition-metal complexes for which reliable reference data have been obtained at the OPBE/TZ2P(STO) level. For several systems, we have used single and double spin-contamination corrections to avoid ambiguity of the results because of spin contamination, that is, the energies and geometries were obtained for the pure spin states. The spin ground states as predicted by the spin-state-corrected GTO basis sets (s6-31G, s6-31G*) are in complete agreement with the reference Slater-type orbital (STO) data, while those of the original basis sets and a recent modification by Baker and Pulay (m6-31G*) are not for all cases. The spin-state-corrected GTO basis sets also improve upon the original and modified basis sets for the accuracy of geometry optimization, while the accuracy of the vibrational frequencies is as good or better. At a limited additional cost, one therefore obtains very reliable results for these important spin-state energies.

Journal of Materials Chemistry

Probing the local structures and protonic conduction pathways in scandium substituted BaZrO₃ by multinuclear solid-state NMR spectroscopy

Lucienne Buannic ^a, Frédéric Blanc ^a, Ivan Hung ^b, Zhehong Gan ^b and Clare P. Grey *^ac

A comprehensive multinuclear solid-state NMR study of scandium-substituted BaZrO₃ is reported. Static low field and MQMAS very high field ⁴⁵Sc NMR data revealed the presence of both 5- and 6-coordinated scandium atoms, 5-coordinated scandium arising from Sc nearby an oxygen vacancy. ¹⁷O NMR spectra showed the presence of up to three different chemical oxygen environments assigned to Zr–O–Zr, Zr–O–Sc and Sc–O–Sc. From the ratios of these different oxygen sites, the distribution of the scandium cations was close to random but indicated that the maximum scandium incorporation was lower than expected, consistent with the observation of Sc₂O₃ impurities at substitution levels of 30% Sc for Zr. ¹H and ⁴⁵Sc NMR data on the hydrated materials revealed the presence of scandium next to protonic defects. Finally, variable temperature ¹H NMR showed the presence of at least two different proton environments in between which proton transfer occurs at ambient temperatures (300 K).

http://www.rsc.org/delivery/_ArticleLinking/ArticleLinking.cfm?JournalCode=JM&Year=2010&ManuscriptID=c0jm00155d&Iss=Advance_Article

DOI: 10.1039/c0jm00155d

Journal of Physical Chemistry B and C, v114, Issues 23

Crystalline Aluminum Hydroxide Fluorides AlFx(OH)3−x·H2O: Structural Insights from 1H and 2H Solid State NMR and Vibrational Spectroscopy

G. Scholz*, S. Brehme, R. Knig, D. Heidemann and E. Kemnitz*
J. Phys. Chem. C, 2010, 114 (23), pp 10535–10543
DOI: 10.1021/jp1023857

AbstractFor the first time, 1H/2H MAS NMR signals of crystalline hydroxide fluorides AlFx(OH)3−x·H2O, as well as of the dehydrated samples, both with pyrochlore structure, were resolved, identified, and assigned in direct correlation with vibrational bands of respective FT IR spectra. The use of magnetically diluted samples in combination with 1H spin−echo experiments, 2H MAS, and 19F−2H CP and 1H−2H CP MAS NMR experiments gave information on different 2H (1H) sites in relation to present structural motifs known from the crystal structure.

Angewandte Chemie International Edition

Angewandte Chemie International Edition
Early View (Articles online in advance of print)
Published Online: 8 Jun 2010

High-Resolution Studies of Uniformly 13C,15H-Labeled RNA by Solid-State NMR Spectroscopy

Alexey V. Cherepanov, Dr., Clemens Glaubitz, Prof. Dr., Harald Schwalbe, Prof. Dr.

Keywords: conformational analysis • freeze-quenching • NMR spectroscopy • RNA • solid-state structures

Abstract: Chilling out: Solid-state 13C NMR correlation spectroscopy was used to assign the signals of a uniformly labeled RNA hairpin infrozen aqueous solution. Conformational analysis shows that solutions of biologically relevant RNAs can freeze withoutsignificant changes in RNA structure and without critical loss of resolution and sensitivity in NMR experiments.

10.1002/anie.200906885


Angewandte Chemie International Edition
Early View (Articles online in advance of print)
Published Online: 8 Jun 2010

The Elusive Enamine Intermediate in Proline-Catalyzed Aldol Reactions: NMR Detection, Formation Pathway, and Stabilization Trends

Markus B. Schmid, Kirsten Zeitler, Dr., Ruth M. Gschwind, Prof. Dr.

Keywords: aldol reaction • enamines • NMR spectroscopy • organocatalysis • proline catalysis

Abstract: The missing link: The elusive enamine intermediate of nucleophilic proline catalysis was detected and stereochemicallycharacterized by NMR analysis of the aldehyde self-aldolization reaction in dipolar aprotic solvents. NMR exchange spectroscopy(EXSY) was used to observe direct enamine formation from oxazolidinones. Additionally, the stabilization of the intermediate bythe appropriate choice of solvent and substitution pattern on the aldehyde is presented.

10.1002/anie.200906629

Phys. Chem. Chem. Phys. 2010 Vol. 12 Issue 22

An entire issue dedicated to dynamic nuclear polarization NMR (cross polarization from an added paramagnetic agent to the nucleus of interest). Requires additional hardware but it is an interesting concept. The following is a good introductory journal:

Solid-state dynamic nuclear polarization at 263 GHz: spectrometer design and experimental results

Melanie Rosay, Leo Tometich, Shane Pawsey, Reto Bader, Robert Schauwecker, Monica Blank, Philipp M. Borchard, Stephen R. Cauffman, Kevin L. Felch, Ralph T. Weber, Richard J. Temkin, Robert G. Griffin and Werner E. Maas

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Dynamic Nuclear Polarization (DNP) experiments transfer polarization from electron spins to nuclear spins with microwave irradiation of the electron spins for enhanced sensitivity in nuclear magnetic resonance (NMR) spectroscopy. Design and testing of a spectrometer for magic angle spinning (MAS) DNP experiments at 263 GHz microwave frequency, 400 MHz 1H frequency is described. Microwaves are generated by a novel continuous-wave gyrotron, transmitted to the NMR probe via a transmission line, and irradiated on a 3.2 mm rotor for MAS DNP experiments. DNP signal enhancements of up to 80 have been measured at 95 K on urea and proline in water–glycerol with the biradical polarizing agent TOTAPOL. We characterize the experimental parameters affecting the DNP efficiency: the magnetic field dependence, temperature dependence and polarization build-up times, microwave power dependence, sample heating effects, and spinning frequency dependence of the DNP signal enhancement. Stable system operation, including DNP performance, is also demonstrated over a 36 h period.

http://www.rsc.org/ej/CP/2010/c003685b.pdf

J. Phys. Chem B and C., vol. 114, Issues 22

Multireference Ab Initio Calculations of g tensors for Trinuclear Copper Clusters in Multicopper Oxidases

Steven Vancoillie‡, Jakub Chalupsk§, Ulf Ryde, Edward I. Solomon, Kristine Pierloot‡, Frank Neese¶* and Lubomr Rulek§*

J. Phys. Chem. B, 2010, 114 (22), pp 7692–7702
DOI: 10.1021/jp103098r

Abstract: EPR spectroscopy has proven to be an indispensable tool in elucidating the structure of metal sites in proteins. In recent years, experimental EPR data have been complemented by theoretical calculations, which have become a standard tool of many quantum chemical packages. However, there have only been a few attempts to calculate EPR g tensors for exchange-coupled systems with more than two spins. In this work, we present a quantum chemical study of structural, electronic, and magnetic properties of intermediates in the reaction cycle of multicopper oxidases and of their inorganic models. All these systems contain three copper(II) ions bridged by hydroxide or O2− anions and their ground states are antiferromagnetically coupled doublets. We demonstrate that only multireference methods, such as CASSCF/CASPT2 or MRCI can yield qualitatively correct results (compared to the experimental values) and consider the accuracy of the calculated EPR g tensors as the current benchmark of quantum chemical methods. By decomposing the calculated g tensors into terms arising from interactions of the ground state with the various excited states, the origin of the zero-field splitting is explained. The results of the study demonstrate that a truly quantitative prediction of the g tensors of exchange-coupled systems is a great challenge to contemporary theory. The predictions strongly depend on small energy differences that are difficult to predict with sufficient accuracy by any quantum chemical method that is applicable to systems of the size of our target systems.