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We introduce an NMR method to help in the analysis of complex mixtures. The spectra of molecular fragments are obtained as the traces of a correlation spectrum of the regular [sup.1]H NMR spectrum on one dimension with the one of the highest possible [sup.1]H multiple-quantum (MaxQ) order. As this latter is a function of the number of distinguishable protons in a given molecular fragment, the analysis of a series of multiple-quantum spectra is required to achieve a complete assignment. This MaxQ NMR approach is likely to perform best in the case of signals concentrated in a very narrow frequency range, which is a challenging situation commonly encountered in many relevant analytical problems such as the characterization of extraction fractions (oil, plants, tissues), biological fluids, or environmentally relevant samples. As a demonstration, we apply the MaxQ NMR analysis to a mixture of 11 poly- and monocyclic aromatic hydrocarbons. 10.1021/ac100009y

The particular molecule discussed in some detail herein is the methyl radical, C[H.sub.3], with emphasis on its potential extraterrestrial appearance. In earlier papers, including group-theoretical analysis, it was shown that the isotropic EPR spectra of free radical (S = 1/2) species [XL.sub.n], where the n equivalent nuclei also have spin 1/2, have a more complicated form than disclosed by the usual (first-order) oversimplified analysis. In the present work, we focus on the magnetic resonance of such systems at or near zero external magnetic field, and on the spectra obtained both by perpendicular [B.sub.1] || B and parallel-field [B.sub.1] k B excitation. This work summarizes what is known about the spin-flip transitions of C[H.sub.3], and predicts what likely will be observed (0-200 MHz, under various field and scan conditions), for the future use by astrophysicists. PACS Nos: 31.30.Gs, 51.60.+a, 52.70.Ds, 76.30.-v, 76.30.Rn, 95.30.Ky, 95.75.Fg, 95.85.Bh, 96.30.-t, 97.20.Vs Nous etudions ici en detail le radical methyle C[H.sub.3], en insistant sur son interet pour les observations astrophysiques. Dans des publications anterieures basees sur la theorie des groupes, il a ete demontre que les spectres isotropes EPR des radicaux libres (S = 1/2) du type [XL.sub.n], ou les n noyaux ont egalement un spin 1/2, ont une forme plus compliquee que celle proposee par l'habituelle analyse tres simplifiee du premier ordre. Ici, nous focalisons sur la resonance magnetique de tels systemes dans un champ magnetique nul ou presque et sur les spectres obtenus dans les deux excitations ou [B.sub.1] [perpendicular to] B et [B.sub.1] || B. Ce travail resume ce qui est connu au sujet des transitions de renversement de spin du C[H.sub.3] et predit ce qui sera vraisemblablement observe (entre 0 et 200 MHz, sous differentes conditions de champ et de balaya[g.sub.e]) dans les observations astrophysiques a venir. [Traduit par la Redaction], 1. Introduction This paper initially was planned to be a continuation of earlier ones [1-3], entitled Magnetic resonance in systems with equivalent spin-1/2 nuclides. Planned part 4: Zero-field and Pi [...]

In this article, we study a class of control problems which involves controlling a continuum of dynamical systems with different values of parameters characterizing the system dynamics by using the same control signal. We call such problems control of ensembles. The motivation for looking into these problems comes from the manipulation of an ensemble of nuclear spins in Nuclear Magnetic Resonance (NMR) spectroscopy and imaging (MRI) with dispersions in natural frequencies and the strengths of the applied radio frequency (rf) field. From the standpoint of mathematical control theory, the challenge is to simultaneously steer a continuum of systems between points of interest with the same control input. This raises some new and unexplored questions about controllability of such systems. We show that controllability of an ensemble can be understood by the study of the algebra of polynomials defined by the noncommuting vector fields that govern the system dynamics. A systematic study of these systems has immediate applications to broad areas of control of ensembles of quantum systems as arising in coherent spectroscopy and quantum information processing. The new mathematical structures appearing in such problems are excellent motivation for new developments in control theory. Index Terms--Ensemble control, ensemble controllability, Lie bracketing, nuclear magnetic resonance (NMR), polynomial approximation.

The outline of a universal cell-free transition system capable of site-specific insertion of any types of labeled amino acids is presented. The system could find potential use for an NMR spectroscopy and also study selected functional aspects of number of proteins.

The critical current and index value of Bi-2223/Ag superconductor is evaluated in high magnetic field. The Bi-2223/Ag conductor has reached enough potential to realize high field applications over 1 GHz NMR spectrometer.

A new tool known as the NMR Mosaic is developed which can be successfully used at universities and colleges to interpret proton NMR.

Various NMR spectroscopic studies are conducted to demonstrate the role of C-boron enolates on the reaction of borane (B[H,sub.3]) and ethyl diazoacetate (EDA), which gives rise to several dimers, trimer and oligomers of EDA. The analysis reveals that the C-boron enolate species are much more stable than its isomeric O-enolates that normally leads to the formation of a doubly generated enolate as the side product of the reaction.

The catalyst discovery, reaction scope and the mechanism of an efficient catalytic method that is used for an efficient conversion of epoxides to succinic anhydrides is studied. The analysis shows that the reaction occurs in two sequential and overlapping stages.

The solid-state NMR spectroscopy technique is employed to study and describe the coupling of functional hydrogen bonds in the models of the confactor pyridoxal-5'-phosphate (PLP) with carboxylic acids that mimic the confactor of various enzyme active sites. The analysis proves a shift in the proton to the Schiff based nitrogen, followed by an increase in the positive charge of the nitrogen atom, which can be avoided by introducing an aromatic substituent in the model.

The NMR titration methods, applicable to a mixture of isotopologues are employed to study various secondary deuterium isotope effects (IEs) on the acidity of several carboxylic acids and phenols. The results of the analysis clearly prove that though the delocalization for aromatic acids does not account for the constancy of IEs from the deuterium, the observed IEs are always consistent with the vibrational frequencies and electron densities.

The gauge-including projector-augmented planewave (GIPAW) density functional theory (DFT) is used to study and describe the NMR chemical shifts in several functionalized single-walled carbon nanotubes (SWNTs). The analysis reveals that a decrease in the degree of functionalization of the system on addition of another group shifts the average chemical shift of the unfunctionalized carbons, but does not affect the shifts of the functionalized carbons.

The study employs off-resonance relaxation NMR spectroscopy to report the saturation difference transfer involved in the formation of amyloid [beta]-peptide (A[beta]) fibrils in human plasma by using the human serum albumin (HSA). The analysis reveals that the described model is widely used to cure Alzheimer's disease, in addition to its ability of investigating the mechanism of action of other oligomerization inhibitors of other amyloidogenic systems as well.

C40/82A (a double mutant) and P27A C40/82A (a triple mutant) barstar mutants were compared using [super 19]F NMR technique. It was found that [super 19]F gives structural information in both the double and triple mutants and the P27A mutant causes significant structural, motional and folding changes to distant core residues.

The solution structure of the poly (A)-binding protein (PABC) domain from wheat PABP and its interaction with the plant PABP-interacting motifs (PAM)-2 sequence via NMR spectroscopy and isothermal calorimetry are described. It is shown that wheat PABC binds to the plant PAM-2 with high affinity through a conserved mechanism suggesting that these proteins are potential plant PABP binding partners.

Diffusion-ordered NMR spectroscopy (DOSY NMR) is a highly useful tool for the study of complex mixtures via NMR. Often, spectral overlap limits the ability of obtaining cleanly separated subspectra of the components due to inherently instable multiexponential fits or data inversion procedures. Three-dimensional DOSY variants offer the advantage of separating individual peaks in an additional dimension, such that robust monoexponential fits to cross-peaks may be used to determine the diffusion coefficients with higher accuracy. For sensitivity reasons, methods based on proton nuclei are preferable. We show that a double-quantum-filtered COSY-DOSY experiment provides advantages over COSY-DOSY, while high signal-to-noise ratios are maintained. We demonstrate the viability of the technique by applying it to a solution of single-stranded DNA oligomers and to a mixture of unprocessed beeswax and decanol.

Whereas the hyphenation of gas chromatography (GC) with mass spectrometry is of great importance, little is known about the coupling to nuclear magnetic resonance spectroscopy (NMR). The investigation of this technique is an attractive proposition because of the valuable information given by NMR on molecular structure. The experiments shown here are to our knowledge the first hyphenating capillary GC to microcoil NMR. In contrast to liquids, gases have rarely been investigated by NMR, mainly due to the experimental difficulties in handling gases and the low signal-to-noise-ratio (SNR) of the NMR signal obtained at atmospheric pressure. With advances in NMR sensitivity (higher magnetic fields and solenoidal microprobes), this limitation can be largely overcome. In this paper, we describe the use of a custom-built solenoidal NMR microprobe with an active volume of 2 [micro]L for the NMR detection of several compounds at 400 MHz, first in a mixture, and then with full coupling to capillary GC to identify them separately. The injected amounts of each analyte in the hyphenated experiments are in the range of 15-50 [micro]mol, resulting in reasonable SNR for sample masses of 1-2 [micro]g.

Structural information on divalent cations such as [Mg.sup.2+] should have important implications for magmatic liquids because of their abundance in the Earth's interior; nevertheless, little is confirmed about their coordination environments. We here apply a [sup.25]Mg triple-quantum magic-angle spinning (3QMAS) NMR technique at an ultra-high magnetic field (21.8 T) and successfully show the occurrence of multiple Mg sites in MgSi[O.sub.3] glass. We find that these sites are distinguished by the degree of polyhedral distortion, not by the coordination number. The present study concludes that the highly distorted Mg[O.sub.6] species occur in MgSi[O.sub.3] glass, in strong contrast with a recent radial distribution study. Keywords: Mg local environment, MgSi[O.sub.3] glass, [sup.25]Mg 3QMAS NMR, ultra-high magnetic field

The local structural environments in a series of natural and synthetic alunite samples [ideally A[Al.sub.3][(S[O.sub.4]).sub.2][(OH).sub.6], A = [H.sub.3][O.sup.+],[ D.sub.3][O.sup.+], [Na.sup.+], and [K.sup.+]] have been probed by solid-state [sup.1]H, [sup. 2]H, [sup. 23]Na, [27.sup]A1, and [sup.39]K NMR spectroscopy. The natural alunite [K[Al.sub.3][(S[O.sub.4]).sub.2][(OH).sub.6] and synthetic hydronium alunite samples contain few structural defects, whereas the synthetic natroalunite and alunite samples have ca. 10% Al vacancies based on [sup.27]A1 NMR. A new [sup.27]A1 local environment (AID) was observed and assigned to Al with one A1 vacancy in the first cation sphere. Three different proton environments, [Al.sub.2]-OH, AlO[H.sub.2], and [H.sub.3][O.sup.+] are detected by [sup.1]H and [sup.2]H MAS NMR. The hydronium ion ([H.sub.3][O.sup.+]) is only observed in hydronium alunite, and is associated with the stoichiometric regions of the sample. It was not detected in [sup.1]H and [sup.2]H NMR spectra of alunite and natroalunite despite K (Na) occupancies of significantly less than 100%, as determined from elemental analysis. Thus, our NMR results suggest that the common assumption, namely that an A vacancy and an [Al.sup.3+] vacancy are compensated by adding an [H.sub.3] [O.sup.+] and 3[H.sup.+] (creating 3 Al-O[H.sub.2] groups), respectively, is too simplistic. Instead, a significant fraction of the [Al.sup.3+] vacancies are compensated for by 4 [H.sup.+] ions, resulting in 4 Al-O[H.sub.2] groups per vacancy. This substitution is accompanied by the simultaneous deprotonation of a [H.sub.3] [O.sup.+] ion present on the A site. The resultant [H.sub.2]O molecule is unnecessary for charge balance, accounting for the A-site deficiency often observed. The presence of [Al.sup.3+] and [A.sup.+] vacancies appears closely correlated based on NMR. Keywords: Alunite, solid-state NMR, hydronium ion, [sup.23]Na NMR, [sup.27]Al NMR, [sup.1]H NMR, [sup.2]H NMR, [sup.39]K NMR

Multidimensional NMR spectroscopy is used to determine the solution structure of the Rhodobacter sphaeroides PufX membrane protein expressed in Escherichia coli. It is found that the overall structure of the PufX is similar to light-harvesting complexes (LH1) [alpha]- and [beta]-polypeptides from Rhodospidrillum rubrum and LH2 polypeptides.

Fluxes through known metabolic pathways and the presence of novel metabolic reactions are often determined by feeding isotopically labeled substrate to an organism and then determining the isotopomer distribution in amino acids in proteins. However, commonly used techniques to measure the isotopomer distributions require derivatization prior to analysis (gas chromatography/mass spectrometry (GC/MS)) or large sample sizes (nuclear magnetic resonance (NMR) spectroscopy). Here, we demonstrate the use of Fourier transform-ion cyclotron resonance mass spectrometry with direct infusion via electrospray ionization to rapidly measure the amino acid isotopomer distribution in a biomass hydrolysate of the soil bacterium Desulfovibrio vulgaris Hildenborough. By applying high front-end resolution for the precursor ion selection followed by sustained off-resonance irradiation collision-induced dissociation, it was possible to determine exactly and unambiguously the specific locations of the labeled atoms in the amino acids, which usually requires a combination of 2-D [sup.13]C NMR spectroscopy and GC/MS. This method should be generally applicable to all biomass samples and will allow more accurate determination of metabolic fluxes with less work and less sample.

A mechanistic study is used to determine the catalytic cycle and its dependence on the ligand, bipyridine (bipy) or isopropyl-phosphinooxazoline ([super i]PrPHOX). The presence of styrene in this system has increased rate-limiting oxidative addition and has promoted the cycle that proceeds four times more rapidly and with much higher enantioselectivity than its styrene-lacking counterpart.

The synthesis and NMR structural studies of eight cyclic modular [beta]-sheets and one linked cyclic modular [beta]-sheet are described. The results have shown that both monovalent and multivalent cyclic modular [beta]-sheets are potential tools that mimic [beta]-sheet interactions involving proteins and inhibit those interactions.

X-ray and NMR techniques were used to study the structure and topology of quadruplexes based on repeats of the human telomeric sequence d(TTAGGG). The results reveal that the DNA quadruplex topology is parallel-stranded with external double-chain-reversal propeller loops.

The structures of neuronal scaffolding proteins neurabin and spinophilin PDZ domain that play an important role in the regulation of synaptic transmission was determined by using biomolecular NMR spectroscopy. The results reveal that the ability to bind to glutamate receptor subunits suggests that the PDZ domains of neurabin and spinophilin are important for targeting protein phosphatase to C-terminal phosphorylation sites.

The H-NS protein, a major component of the nucleoid in Gram-negative bacterial cells, forms bridges between different DNA molecules or between different sections of the same molecule, facilitating it to compact and impose structure on nucleoid. New insights into H-NS mediated DNA bridging that were obtained using tweezers device are described.

The structure and structural properties of nuclear receptors is described focusing on the ligand-binding and DNA binding domains and unstructured N-terminal regions. To emphasize the allosteric interdependence among these subunits, a more detailed inspection of the structural properties of the human progesterone receptor is presented.