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Nuclear magnetic resonance (NMR) is a powerful method for determining the structure of molecules and proteins.sup.1. Whereas conventional NMR requires averaging over large ensembles, recent progress with single-spin quantum sensors.sup.2-9 has created the prospect of magnetic imaging of individual molecules.sup.10-13. As an initial step towards this goal, isolated nuclear spins and spin pairs have been mapped.sup.14-21. However, large clusters of interacting spins--such as those found in molecules--result in highly complex spectra. Imaging these complex systems is challenging because it requires high spectral resolution and efficient spatial reconstruction with sub-ångström precision. Here we realize such atomic-scale imaging using a single nitrogen vacancy centre as a quantum sensor, and demonstrate it on a model system of 27 coupled .sup.13C nuclear spins in diamond. We present a multidimensional spectroscopy method that isolates individual nuclear-nuclear spin interactions with high spectral resolution (less than 80 millihertz) and high accuracy (2 millihertz). We show that these interactions encode the composition and inter-connectivity of the cluster, and develop methods to extract the three-dimensional structure of the cluster with sub-ångström resolution. Our results demonstrate a key capability towards magnetic imaging of individual molecules and other complex spin systems.sup.9-13. An individual electron is used as a quantum sensor to realize atomic-scale magnetic resonance imaging., Author(s): M. H. Abobeih [sup.1] [sup.2] , J. Randall [sup.1] [sup.2] , C. E. Bradley [sup.1] [sup.2] , H. P. Bartling [sup.1] [sup.2] , M. A. Bakker [sup.1] [sup.2] , [...]

A geometrical approach to the analysis of a data bank containing information on space structures of proteins is suggested. As a result of the analysis, several relationships concerning possible conformations are found, and also there is obtained a list of polypeptides whose structures differ essentially from typical concepts of the 3D-structure of proteins. Those deviations could indicate possible errors and gaps of the interpreting models in use, as well as some new unknown relations and rules., UDC 514.8+51-76+57.087 1. Introduction In the present paper, we demonstrate the potential of a geometrical approach to verification and analysis of information on space structure of proteins. Today the study [...]

The reactivity and complexation properties of dicoordinated Sn(II) and Sn(0) compounds are reviewed. The (dominant) electrophilicity of the stannylenes was confirmed and quantified through density functional theory (DFT) based reactivity indices. For these compounds, combining theoretical DFT calculations and experimental nuclear magnetic resonance (NMR) spectroscopic results has evidenced their potential to undergo n-complexation from aromatic n clouds in addition to significantly stronger cr-complexation. Moreover, their potential as Lewis bases was scrutinized in their interactions and reactions with iron and tungsten carbonyl Lewis acids. Finally, a prospective comparison of the reactivity of divalent stannylenes and stannylones, with a 0 oxidation state at the Sn atom, is presented. Key words: dicoordinate tin compounds, [sup.119]Sn NMR spectroscopy, conceptual density functional theory, stannylenes and stannylones, reactivity. Resume : La reactivite et les proprietes des composes dicoordonnes Sn(II) et Sn(0) sont examinees. Le caractere electrophile (dominant) des stannylenes a ete confirme et calcule a l'aide des indices de reactivite bases sur la theorie de la fonctionnelle de la densite (DFT). Des calculs de DFT associes a des resultats experimentaux obtenus par spectroscopie RMN ont mis en evidence que ces composes pouvaient subir, outre des tres fortes r-complexations, des n-complexations a partir de nuages n aromatiques. De plus, leur potentiel en tant que bases de Lewis a ete minutieusement analyse lors de leurs interactions et reactions avec les acides de Lewis que sont le carbonyle de fer et le carbonyle de tungstene. Enfin, une comparaison eventuelle entre la reactivite des stannylenes divalents et celle des stannylones, l'atome Sn se trouvant dans un etat d'oxydation 0, est presentee. [Traduit par la Redaction] Mots-cles : composes d'etain dicoordonnes, spectroscopie RMN [sup.119]Sn, theorie de la fonctionnelle de la densite conceptuelle, stannylenes et stannylones, reactivite., Introduction It is well known that the dominant oxidation state of group 14 element coordination and organometallic compounds is +IV. However the +II oxidation state is also known for all [...]

Seven natural analcime samples with atomic Si/Al ratios from 1.97 to 2.63 were investigated to explore the effects of intermediate range structure and A1 for Si substitution up to the fourth nearest neighbor coordination shell on the [sup.29]Si NMR chemical shifts in the framework aluminosilicates. With increasing bulk Si/A1 ratio, the [sup.29]Si chemical shifts of all Si(nAl) resonances become more negative (more shielded), consistent with previously reported trends for faujasite and LTA zeolite (Newsam 1985). For our analcimes, the total observed changes in chemical shift for the Si(3Al), Si(2A1), and Si(1A1) sites are ~0.5, 0.6, and l. 1 ppm, respectively, demonstrating that the effect of Si/Al ratio is more significant for the Si sites with a smaller number of next-nearest neighbor A1 atoms. The mean value of the change in chemical shift per added A1 on fourth nearest neighbor sites is ~2.8 ppm [2.3 ppm if Si(3Al) is excluded]. This value is similar to the results of recent QM/MM calculations and is somewhat larger than those previously reported for faujasite and LTA framework zeolite (~1.4 and 1.3 ppm). This difference correlates with the overall denser structure of analcime, including smaller cages and shorter Si-fourth neighbor distances. Combining these results with the known changes in [sup.29]Si chemical shifts for framework silicates due to changes in the first coordination shell, tetrahedral polymerization and second neighbor A1 for Si substitution for tetrahedrally coordinated Si, we present an empirical relation between the changes in [sup.29]Si chemical shift and interatomic distance between Si and nearby atoms. Keywords: Analcime, intermediate range structure, [sup.29]Si NMR, Si/A1 ratio, fourth nearest neighbor DOI: 10.2138/am.2010.3476

Forsterite ([Mg.sub.2]Si[O.sub.4]) is a silicate mineral frequently studied in the Earth sciences as it has a simple crystal structure and fast dissolution kinetics (elemental release rates under typical conditions on the order of [l0.sup.-7] mol/[m.sup.2]/[s.sup.1]). During the dissolution process, spectroscopic techniques are often utilized to augment solution chemical analysis and to provide data for determining reaction mechanisms. Nuclear magnetic resonance (NMR) is able to interrogate the local bonding arrangement and coordination of a particular nuclide to obtain structural information. Although previous NMR studies have focused on the silicon and oxygen environments in forsterite, studies focusing on the two nonequivalent magnesium environments in forsterite are limited to a few single-crystal studies. In this study, we present the results of [sup.25]Mg MAS, MQMAS, and static QCPMG experiments performed on a powdered sample of a pure synthetic forsterite. We also present spectral fits obtained from simulation software packages, which directly provide quadrupolar parameters for [sup.25]Mg nuclei occupying each of the two nonequivalent magnesium sites in the forsterite structure. These results are compared to calculations of the electric field gradient tensor conducted in previous ab initio studies to make definitive assignments correlating each peak to their respective magnesium site in the forsterite structure. Althought previous NMR investigations of forsterite have focused on single-crystal samples, we have focused on powdered forsterite as the increased surface area of powdered samples makes them more amenable to laboratory-scale dissolution studies and, ultimately, the products from chemical weathering may be monitored and quantified. Keywords: Forsterite, magnesium, [sup.25]Mg, NMR, MQMAS, QCPMG DOI: 10.2138/am.2010.3403

The serine protease thrombin is generated from its zymogen prothrombin at the end of the coagulation cascade. Thrombin functions as the effector enzyme of blood clotting by cleaving several procoagulant targets, but also plays a key role in attenuating the hemostatic response by activating protein C. These activities all depend on the engagement of exosites on thrombin, either through direct interaction with a substrate0 as with fibrinogen, or by binding to cofactors such as thrombomodulin. How thrombin specificity is controlled is of central importance to understanding normal hemostasis and how dysregulation causes bleeding or thrombosis. The binding of ligands to thrombin via exosite I and the coordination of [Na.sup.+] have been associated with changes in thrombin conformation and activity. This phenomenon has become known as thrombin allostery, although direct evidence of conformational change, identification of the regions involved, and the functional consequences remain unclear. Here we investigate the conformational and dynamic effects of thrombin ligation at the active site, exosite I and the [Na.sup.+]-binding site in solution, using modern multidimensional NMR techniques. We obtained full resonance assignments for thrombin in seven differently liganded states, including fully unliganded apo thrombin, and have created a detailed map of residues that change environment, conformation, or dynamic state in response to each relevant single or multiple ligation event. These studies reveal that apo thrombin exists in a highly dynamic zymogen-like state, and relies on ligation to achieve a fully active conformation. Conformational plasticity confers upon thrombin the ability to be at once selective and promiscuous. allostery | hemostasis | protease | structure | zymogen doi/ 10.1073/pnas.1005255107

Problem statement: The variations of formyl proton Chemical Shifts (CS) of p-substituted benzaldehydes in aromatic solvents were investigated. The validity of several physical solvent and empirical solvent scales was examined. Also, to predict dipolarity-polarizability ([pi]*) solvent scale for some aromatic solvents. Model designing was also achieved to rationalize the aromatic solvent effect on the formyl proton CS. Approach: The previously recorded formyl proton CS for p-X-benzaldehydes, with X were [NMe.sub.2], OMe, O[C.sub.3][H.sub.7], H, Br, CHO and [NO.sub.2] in benzene, toluene, p-xylene, m-xylene and mesitylene were subjected to Factor Analysis (FA). Target Factor Testing technique (TFT) was performed for several solvent scales namely: Unity, the intrinsic aromatic solvent induced shift of TMS (IASISTMS), f(n), f(d), ([n.sup.2]-1)/([n.sup.2]+2), (d-l)/(d+2), [E.sub.T](30) and [pi]*. Iterative TFT was applied to predict unmeasured ([pi]*) solvent scale for ethyl benzene, n-butyl benzene, sec-butyl benzene, tert-butyl benzene and isopropyl benzene. Results: It has been found that two factors were responsible for the variation in the formyl proton CS. The unity, f(n), ([n.sup.2]-l)/([n.sup.2]+2), IASISTMS, [E.sub.T](30) and [pi]* were real factors. Model designing of the formyl proton CS in benzene, toluene, p-xylene, m-xylene and mesitylene were achieved. The models with lowest root mean square error (RMSE) have shown that Unity is a consistent term. The other term was either IASISTMS or [pi]* . Iterative TFT predicted new [pi]* values for ethylbenzene, n-butylbenzene, sec-butylbenzene, tert-butylbenzene and isopropylbenzene respectively. Conclusion: FA has revealed that two real factors are responsible for the variation of formyl CS in benzene, toluene, p-xylene, m-xylene and mesitylene solvents. TFT has shown to be a powerful technique in predicting new values of the [pi]* solvent scale. Model designing for the formyl proton CS have revealed that the IASISTMS, [pi]* and Unity are the best empirical solvent scales and were better than any physical solvent scales in reproducing the formyl CS. The IASISTMS reflects the dipolarity-polarizabilty of the aromatic solvent. The cofactor of the solvent scale was found to correlate with the [[sigma].sub.p.sup.+] substituent parameter. Key words: Formyl proton NMR chemical shift, factor analysis, principal components analysis, target factor analysis, aromatic solvent effect, dipolarity-polarizability solvent scale, INTRODUCTION It is well-known that a solvent exerts an effect on many solvent dependent properties. These solvent-solute interactions can be related to physicochemical scales by constructing a solvent model (Koppel [...]

Heterodimeric integrin adhesion receptors regulate diverse biological processes including angiogenesis, thrombosis and wound healing. The transmembrane-cytoplasmic domains (TMCDs) of integrins play a critical role in controlling activation of these receptors via an inside-out signaling mechanism, but the precise structural basis remains elusive. Here, we present the solution structure of integrin [alpha]IIb[beta]3 TMCD heterodimer, which reveals a right-handed coiled-coil conformation with 2 helices intertwined throughout the transmembrane region. The helices extend into the cytoplasm and form a clasp that differs significantly from a recently published [alpha]IIb[beta]3 TMCD structure. We show that while a point mutation in the clasp interface modestly activates [alpha]IIb[beta]3, additional mutations in the transmembrane interface have a synergistic effect, leading to extensive integrin activation. Detailed analyses and structural comparison with previous studies suggest that extensive integrin activation is a highly concerted conformational transition process, which involves transmembrane coiled-coil unwinding that is triggered by the membrane-mediated alteration and disengagement of the membrane-proximal clasp. Our results provide atomic insight into a type I transmembrane receptor heterocomplex and the mechanism of integrin inside-out transmembrane signaling. NMR | protein structure | transmembrane domain doi/ 10.1073/pnas.0909589106

Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spcctrometry (MS) is the technique of choice to achieve molecular weight data for synthetic polymers. Because the success of a MALDI-MS analysis critically depends on a proper matrix and cation selection, which in turn relates closely to the polymer chemical nature and size, prior estimation of the polymer size range strongly helps in rationalizing MALDI sample preparation. We recently showed how pulsed gradient spin echo (PGSE) nuclear magnetic resonance could be used as an advantageous alternative to size exclusion chromatography, to rationalize MALDI sample preparation and confidently interpret MALDI mass spectra for homopolymers. Our aim here is to extend this methodology to the demanding case of amphiphilic block copolymers, for which obtaining prior estimates on the [M.sub.w] values appears as an even more stringent prerequisite. Specifically, by studying poly(ethylene oxide) polystyrene block copolymers of distinct molecular weights and relative block weight fractions, we show how PGSE data can be used to derive the block [M.sub.w] values. In contrast to homopolymers, such determination requires not only properly recorded calibration curves for each of the polymers constituting the block copolymers but also an appropriate hydrodynamic model to correctly interpret the diffusion data.

We investigate the effect of the lattice topology (ideal hexagonal rings vs. ditrigonal rings) and cluster size of model clusters (three-ring vs. seven-ring clusters) on the nature of benzyl alcohol adsorption on kaolinite surfaces using quantum chemical calculations with an emphasis on the equilibrium configuration, binding energy, and NMR chemical shielding tensors. The optimized structure of benzyl alcohol adsorbed on the tetrahedral layer of kaolinite varies according to the type and size of model cluster. While the calculated binding energy varies with the level of theory and the basis sets used for the calculations, the binding energies between benzyl alcohol and seven-ring clusters are smaller than those between benzyl alcohol and three-ring clusters partly due to the edge hydrogen for the latter. The results also indicate a stronger binding energy between benzyl alcohol and octahedral surfaces than between benzyl alcohol and tetrahedral layers. Although the calculated binding energies for seven-member rings with varying lattice topologies are rather similar, the detailed optimized structures are distinct, demonstrating the effect of lattice topology on the nature of adsorption. The optimized structures and binding energies indicate that an intermediate degree of hydrogen bonding is dominant for the three-member silicate rings and that the interaction between the benzene ring and basal O atoms in the seven-member rings is characterized by a weak hydrogen bond and dispersion force. The calculated [sup.17]O isotropic chemical shieldings of some basal O atoms decrease up to ~4-5 ppm after the adsorption (with an estimated uncertainty of ~2 ppm). Since the high-resolution [sup.17]O 3QMAS NMR spectroscopy of layer silicates yielded a resolution of 1-2 ppm for the basal oxygen sites in the layer silicates in previous work, the NMR technique may be useful in exploring the nature of adsorption between organic molecules and silicate surfaces, whereas further computational studies on the effect of the basis sets, the surface coverage, and the types of diverse organic molecules with larger model clusters for surfaces remain to be explored. Keywords: Kaolinite, benzyl alcohol, quantum chemical calculations, NMR chemical shielding, lattice topology, surface adsorption

We present the first direct observation of high-coordinated Si and Al occurring together in a series of high-pressure sodium aluminosilicate glasses, quenched from melts at 6 GPa. Using [sup.29]Si MAS NMR, we observe that a small amount of A1 does not have a significant effect on the amount of [sup.V]Si or [sup.VI]Si generated, but that larger Al concentrations lead to a gradual decrease in both these species. [sup.27]Al MAS NMR spectra show that samples with small amounts of Al have extremely high mean Al coordination values of up to 5.49, but that larger Al concentrations cause a gradual decrease in both [sup.V]Al and [sup.VI]Al. Although mean Al and Si coordination numbers both decrease with increasing Al contents, the weighted combined (Al+Si) coordination number increases. Silicon and Al resonances shift in frequency with increasing pressure or changing Al concentration, indicating additional structural changes, including compression of network bond angles. Increases in the [sup.23]Na isotropic chemical shifts indicate decreases in the mean Na-O bond lengths with increasing pressure, which are more dramatic at higher Al contents. Recovered glass densities are about 10 to 15% greater than those of similar ambient pressure samples. However, the density increases due to the combined coordination changes of Al and Si are estimated to total only about 1 to 2%, and are roughly constant with composition despite the large effects of Al content on the individual coordinations of the two cations. Thus, effects of other structural changes must be significant to the overall densification. Apparent equilibrium constants for reactions involving the generation of high-coordinated species show systematic behavior, which suggests an internal consistency to the observed Si and Al coordination number shifts. Keywords: NMR, aluminosilicate, glass, high pressure, coordination, aluminum, silicon, sodium

Arsenate ([As.sup.5+]) substitution in the hydroxylapatite structure was examined using a combination of crystallographic and spectroscopic techniques. Samples of hydroxylapatite, the [As.sup.5+]-substituted analog (synthetic johnbaumite), and five intermediate compositions were synthesized from solution. Synchrotron X-ray diffraction data show that all samples are single-phase, confirming complete substitution. No evidence is found for lowering of symmetry below [P6.sub.3]/m. Rietveld structure refinements show progressive expansion of the unit cell with increasing As substitution, which can be accounted for primarily by an average expansion of the tetrahedral site. Sizes of Ca polyhedra show little variation as a result of As substitution. NMR results show no evidence for local clustering of P[O.sub.4] tetrahedra. EXAFS confirms that the size of As-centered tetrahedra remains constant across the solid-solution series. Keywords: Apatite, hydroxylapatite, johnbaumite, arsenic, arsenate, NMR, EXAFS

A metabolomics approach combining [sup.1]H NMR and gas chromatography--electrospray ionization time-of-flight mass spectrometry (GC--EI-TOFMS) profiling was employed to characterize melon (Cucumis melo L.) fruit. In a first step, quantitative [sup.1]H NMR of polar extracts and principal component analyses (PCA) of the corresponding data highlighted the major metabolites in fruit flesh, including sugars, organic acids, and amino acids. In a second step, the spatial localization of metabolites was investigated using both analytical techniques. Direct [sup.1]H NMR profiling of juice or GC--EI-TOFMS profiling of tissue extracts collected from different locations in the fruit flesh provided information on advantages and drawbacks of each technique for the analysis of a sugar-rich matrix such as fruit. [sup.1]H NMR and GC--EI-TOFMS data sets were compared using independently performed PCA and multiblock hierarchical PCA (HPCA), respectively. In addition a correlation-based multiblock HPCA was used for direct comparison of both analytical data sets. These data analyses revealed several gradients of metabolites in fruit flesh which can be related with differences in metabolism and indicated the suitability of multiblock HPCA for correlation of data from two (or potentially more) metabolomics platforms.

In this manuscript, the remarkable NMR signal enhancement that can be provided by dynamic nuclear polarization (DNP) was combined with the reactivity of acetic anhydride with amines to perform rapid, high SNR analyses of amino acid mixtures and to hyperpolarize new biomolecules of interest. [1,1-[sup.13]C] acetic anhydride is an excellent substrate for DNP hyperpolarization because it can be well polarized in only 30 min and has a relatively long T1 relaxation time (33.9 s at 11.7 T and 37[degrees]C). The secondary hyperpolarization approach developed in this project takes advantage of the preferential reaction of acetic anhydride with amine nucleophiles, which occurs much more rapidly than hydrolysis to produce hyperpolarized N-acetyl adducts. This new approach was used to reproducibly and near-quantitatively (mean yield--89.8%) resolve a mixture of amino acids Gly, Ser, Val, Leu, and Ala in a single acquisition (3 s) with a signal enhancement of up to 1,400-fold as compared with thermal equilibrium. Secondary hyperpolarization was performed for several small peptides and N-acetylcysteine, a drug administered intravenously to treat acetaminophen overdose. Although, in general the [T.sub.1] of the N-acetyl adducts decreased with increasing molecular weight of the biomolecules, the [T.sub.1] values were still on the order of 10 s, and the correlation of [T.sub.1] with molecular weight was not exact suggesting the potential of secondarily polarizing relatively large biomolecules. This study demonstrates the feasibility of using prepolarized [1,1-[sup.13]C] acetic anhydride and rapid chemical reactions to provide high SNR NMR spectra of amino acid derivatives and other biomolecules. acetylation | metabolism | peptides | spectroscopy

Conversion of lactate to glucose was examined in myotubes, minced muscle tissue, and rats exposed to [sup.2][H.sub.2]O or [sup.13]C-enriched substrates. Myotubes or minced skeletal muscle incubated with [U-[sup.13][C.sub.3]]lactate released small amounts of [1,2,3-[sup.13][C.sub.3]]- or [4,5,6-[sup.13][C.sub.3]]glucose. This labeling pattern is consistent with direct transfer from lactate to glucose without randomization in the tricarboxylic acid (TCA) cycle. After exposure of incubated muscle to [sup.2][H.sub.2]O, [U-[sup.13][C.sub.3]]lactate, glucose, and glutamine, there was minimal release of synthesized glucose to the medium based on a low level of [sup.2]H enrichment in medium glucose but 50- to 100-fold greater [sup.2]H enrichment in glucosyl units from glycogen. The [sup.13]C enrichment pattern in glycogen from incubated skeletal muscle was consistent only with direct transfer of lactate to glucose without exchange in TCA cycle intermediates, [sup.13]C nuclear magnetic resonance (NMR) spectra of glutamate from the same tissue showed flux from lactate through pyruvate dehydrogenase but not flux through pyruvate carboxylase into the TCA cycle. Carbon from an alternative substrate for glucose production that requires metabolism through the TCA cycle, propionate, did not enter glycogen, suggesting that TCA cycle intermediates do not exchange with phosphoenolpyruvate. In vivo, the [sup.13]C labeling patterns in hepatic glycogen and plasma glucose after administration of [U-[sup.13][C.sub.3]]lactate did not differ significantly. However, skeletal muscle glycogen was substantially enriched in [1,2,3-[sup.13][C.sub.3]]- and [4,5,6-[sup.13][C.sub.3]]glucose units that could only occur through skeletal muscle glyconeogenesis rather than glycogenesis. Lactate serves as a substrate for glyconeogenesis in vivo without exchange into symmetric intermediates of the TCA cycle. pyruvate kinase; phosphoenolpyruvate carboxykinase; glyconeogenesis; nuclear magnetic resonance; skeletal muscle

Condensed organic matter (OM) such as nonhydrolyzable C (NHC) is important in C cycling and the sorption and fate of hydrophobic organic contaminants in soils and sediments, but its structural components are rarely known. Nonhydrolyzable C in three contaminated soils and 22 bulk and size-fractionated sediments from the Pearl River delta and estuary in China were measured following treatment with an HCl-HF-trifluoroacetic acid method. It was characterized using elemental analysis, radiocarbon accelerated mass spectroscopy, and Raman microspectrometry. The results show that NHC is an important or even dominating component of the organic C (OC) in the investigated soils and sediments. The NHC contents in this study are highly correlated with the OC contents, with a slope of 0.647 for the 25 soil and sediment samples, which is higher than previously reported NHC-OC correlations in the soils. The radiocarbon analysis demonstrates the importance of ancient OM in the NHC samples. The NHC fractions are chemically and structurally different from the biopolymer and humic substances in the soils and sediments, and originated from different thermally matured bitumen or kerogens, polymethylene C (algaenan, cutan, cutin, cuticle, and lipid), aged terrigenous OM (lignin and humin), and black carbon. Abbreviations: BC, black carbon; HA, humic acid; NHC, nonhydrolyzable carbon; NMR, nuclear magnetic resonance; NR, North River; OC, organic carbon; OM, organic matter; PRD, Pearl River Delta; SOM, soil and sediment organic matter; TFA, trifluoroacetic acid; WR, West River.

Archaeological waterlogged leathers dated from the 13th to 17th century have been analyzed using carbon-13 high-resolution solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). The NMR and EPR spectra have been compared to modern vegetable-tanned leathers and crude hide. Both techniques allowed us to fully characterize the samples and better understand the changes occurring during aging in water environment. The main features of the archaeological leathers are the high contents in iron and the absence of residual vegetable tannins. Traces of lubricants could not be detected either. The accumulation of iron oxides may have played a role in the conservation of the archaeological objects and explain the surprising good conservation state of the leather samples as was observed in the NMR spectra. The absence of tannins and lubricants in the studied archaeological samples is also discussed. It may be a consequence of aging in water-rich environment. The analysis strategy described in this paper can be systematically applied to characterize archaeological or historical leather samples.

[sup.1]H NMR spectroscopy coupled with multivariate statistical analysis was used for the first time to investigate metabolic changes in musts during alcoholic fermentation and wines during aging. Three Saccharomyces cerevisiae yeast strains (RC-212, KIV-1116, and KUBY-501) were also evaluated for their impacts on the metabolic changes in must and wine. Pattern recognition (PR) methods, including PCA, PLS-DA, and OPLS-DA scores plots, showed clear differences for metabolites among musts or wines for each fermentation stage up to 6 months. Metabolites responsible for the differentiation were identified as valine, 2,3-butanediol (2,3-BD), pyruvate, succinate, proline, citrate, glycerol, malate, tartarate, glucose, N-methylnicotinic acid (NMNA), and polyphenol compounds. PCA scores plots showed continuous movements away from days 1 to 8 in all musts for all yeast strains, indicating continuous and active fermentation. During alcoholic fermentation, the highest levels of 2,3-BD, succinate, and glycerol were found in musts with the KIV-1116 strain, which showed the fastest fermentation or highest fermentative activity of the three strains, whereas the KUBY-501 strain showed the slowest fermentative activity. This study highlights the applicability of NMR-based metabolomics for monitoring wine fermentation and evaluating the fermentative characteristics of yeast strains.

Chemical shift variation in small-molecule [sup.1]H NMR signals of biofluids complicates biomarker information recovery in metabonomic studies when using multivariate statistical and pattern recognition tools. Current peak realignment methods are generally time-consuming or align major peaks at the expense of minor peak shift accuracy. We present a novel recursive segment-wise peak alignment (RSPA) method to reduce variability in peak positions across the multiple [sup.1]H NMR spectra used in metabonomic studies. The method refines a segmentation of reference and test spectra in a top-down fashion, sequentially subdividing the initial larger segments, as required, to improve the local spectral alignment. We also describe a general procedure that allows robust comparison of realignment quality of various available methods for a range of peak intensities. The RSPA method is illustrated with respect to 140 [sup.1]H NMR rat urine spectra from a caloric restriction study and is compared with several other widely used peak alignment methods. We demonstrate the superior performance of the RSPA alignment over a wide range of peaks and its capacity to enhance interpretability and robustness of multivariate statistical tools. The approach is widely applicable for NMR-based metabolic studies and is potentially suitable for many other types of data sets such as chromatographic profiles and MS data.

Managing heavily manured soils for decreased P loss to waters requires improved understanding of the chemical and sorption--desorption characteristics of P in these soils. We used soils from agricultural fields receiving [greater than or equal to] 8 yr of dairy, poultry, swine manure or spent mushroom compost for the determination of P functional groups in NaOH-EDTA extracts by solution [sup.31]P nuclear magnetic resonance (NMR) spectroscopy, degree of P saturation (DPS), and P sorption-desorption isotherms. The [sup.31]P NMR results show that inorganic orthophosphate was the primary form of P in manure treated (79-93% of total extract P) and untreated soils (33-71%). Pyrophosphate and phosphate monoesters were identified in all soils, whereas phosphate diesters were present in small proportions ( Abbreviations: DPS, degree of phosphorus saturation; ICP-AES, inductively coupled plasma-atomic emission spectroscopy; IHP, inositol hexakisphosphate; NMR, nuclear magnetic resonance.

Two simple and straightforward procedures for determining the organic content of hybrid silica materials by means of conventional NMR and GC/MS techniques are described. The methods involve dissolving the hybrid material either in a concentrated solution of sodium hydroxide in deuterated water containing a suitable reference or in a solution of hydrogen fluoride in water and extracting with methylene chloride. These methods constitute useful routine techniques for obtaining immediate information concerning both the amount and chemical composition of the organic compounds on the silica surface.

Analytical analyses of highly complex mixtures, such as biofluids or liquid food products, often give rise to signals for unknown compounds, particularly for compounds at low concentration. Here we compare two conventional chemometric approaches for NMR spectral analysis ('spectral binning' and 'high-resolution analysis') with a novel library-based method ('targeted profiling of unknowns', TPU). The three methods were applied to a proton NMR spectral data set of ultrafiltered mouse serum typical of those examined in metabolomics/metabonomics studies. The advantages of high-resolution analysis of typical NMR peaks have been well described previously, and as a result we examined low intensity unknowns peaks (LIUPs). A total of 25 LIUPs were assessed based on their significance to multivariate statistical analysis of the data set using the TPU method. The linearity of NMR signals at low incremental concentration changes (

Intrinsically disordered proteins play critical but often poorly understood roles in mediating protein interactions. The interactions of disordered proteins studied to date typically entail structural stabilization, whether as a global disorder-to-order transition or minimal ordering of short linear motifs. The disordered cyclin-dependent kinase (CDK) inhibitor Sic1 interacts with a single site on its receptor Cdc4 only upon phosphorylation of its multiple dispersed CDK sites. The molecular basis for this multisite-dependent interaction with a single receptor site is not known. By NMR analysis, we show that multiple phosphorylated sites on Sic1 interact with Cdc4 in dynamic equilibrium with only local ordering around each site. Regardless of phosphorylation status, Sic1 exists in an intrinsically disordered state but is surprisingly compact with transient structure. The observation of this unusual binding mode between Sic1 and Cdc4 extends the understanding of protein interactions from predominantly static complexes to include dynamic ensembles of intrinsically disordered states. disorder | dynamic complex | multisite phosphorylation | NMR | protein interaction

Commercially available partly acetylated glycerols (mono-and diacetins) are a mixture of glycerol, 1- and 2-acetylglycerol, 1,2- and 1,3-diacetylglycerol, and triacetin. No exact analysis method is available. Comparisons of [sup.1]H NMR measurements obtained using deuterated dimethyl sulfoxide (DMSO-[d.sub.6]) and DMSO-[d.sup.6]/15% [D.sub.2]O are sufficient to identify and determine quickly all the components. Advantages compared with the commonly used NMR solvent CD[Cl.sub.3] for fatty acid glycerides include the solubility of all the components and a highly informative OH signal pattern in a region between 4.36 and 5.26 ppm almost free of other signals. 2-Acetylglycerol (2-acetin) is shown to disproportionate even at 50 [degrees]C into a mixture of glycerol and acetylglycerol thereby making it difficult to quantify by liquid chromatography (LC) and gas chromatography (GC) methods. Complete [sup.1]H chemical shift data for all five components allow for the identification of the components in the mixture and thus the determination of the composition. The NMR method with DMSO-[d.sub.6] as solvent was used for acetins, propionins, and butyrins. Semipreparative high-performance liquid chromatography (HPLC) on an RP18 column led to moderately pure 1-monoacetin and a mixture of diacylated species. Electron impact mass spectra show for all the components very characteristic fragmentation patterns with loss of AcOC[H.sub.2] radicals, in contrast to the well-known pattern of longer-chained fatty acid derivatives that show preferred first-step loss of acyl-O radicals.

A NMR microprobe based on microstrip technology suitable for investigations of volume-limited samples in the low nanoliter range was designed. NMR spectra of sample quantities in the 100 pmol range can be obtained with this probe in a few seconds. The planar geometry of the probe is easily adaptable to the size and geometry requirements of the samples.