NMR Spectral Features Research Articles

Multi-Scale Structural Insights into Enzymatically Hydrolyzed Lentil Starch Concentrates Prepared by In Vitro Method Using Different Types of Enzymes.

This study was undertaken to investigate the enzymatic hydrolysis of lentil starch concentrates from conventional cooked seeds (CCLSC) by the action of different types of enzymes, including pancreatin (PC-EHSC), heat-stable α-amylase (HS-EHSC), β-amylase (βA-EHSC), amyloglucosidase (AMG-EHSC), and multi-enzymes (βA-HS-AMG-EHSC); their multi-scale structural characteristics of the enzymatic hydrolysis products of lentil starch concentrates were compared. The morphological features distinguished among different samples. The Fourier-transform infrared spectroscopy and solid-state 13C CP/MAS NMR spectral features indicated the possible formation of a binary and ternary complex among amylose, protein and lipids. The X-ray diffraction results revealed that the V-type characteristic diffraction peaks were more obvious for samples including PC-EHSC and βA-EHSC, which was in line with their lowest polydispersity index (DPn). PC-EHSC and βA-EHSC also showed an increased peak intensity of the scattering maximum on the small-angle X-ray scattering spectra, whereas CCLSC exhibited an overall lower peak intensity within the studied q range of scattering. The highest XRD crystallinity and the lowest DPn value obtained for PC-EHSC indicated that the starch polymers modified by pancreatin could produce glucan chains with a comparatively homogenous Mw distribution that are readily recrystallized by hydrogen bonding through chain aggregation. Comparatively, the lowest relative crystallinity for HS-EHSC obtained from XRD suggested that thermostable α-amylolysis was unfavorable for the formation of starch structure with a higher degree of molecular order. This study could provide useful information for the needed research to obtain a deeper understanding of the impact of different amylolysis actions on the structural organization of starch hydrolysates and to provide a theoretical foundation for the development of fermentable enzymatically hydrolyzed starch with well-tailored physiological properties.

GIPMA: Global Intensity-Guided Peak Matching and Alignment for 2D 1H-13C HSQC-Based Metabolomics.

Two-dimensional (2D) 1H-13C heteronuclear single quantum coherence (HSQC) has been increasingly applied to metabolomics studies because it can greatly improve the resolving capability compared with one-dimensional (1D) 1H NMR. However, preprocessing methods such as peak matching and alignment tools for 2D NMR-based metabolomics have lagged behind similar methods for 1D 1H NMR-based metabolomics. Correct matching and alignment of 2D NMR spectral features across multiple samples are particularly important for subsequent multivariate data analysis. Considering different intensity dynamic ranges of a variety of metabolites and the chemical shift variation across the spectra of multiple samples, here, we developed an efficient peak matching and alignment algorithm for 2D 1H-13C HSQC-based metabolomics, called global intensity-guided peak matching and alignment (GIPMA). In GIPMA, peaks identified in all spectra are pooled together and sorted by intensity. Chemical shift of a stronger peak is regarded to be more accurate and reliable than that of a weaker peak. The strongest undesignated peak is chosen as the reference of a new cluster if it is not located within the chemical shift tolerance of any existing peak cluster (PC), or otherwise it is matched to an existing PC and the aligned chemical shift of the PC is updated as the intensity-weighted average of the chemical shifts of all peaks in the cluster. Setting an optimum chemical shift tolerance (Δδo) is critical for the peak matching and alignment across multiple samples. GIPMA dynamically searches for and intelligently selects the Δδo for peak matching to maximize the number of valid peak clusters (vPC), that is, spectral features, among multiple samples. By GIPMA, fully automatic peakwise matching and alignment do not require any spectrum as initial reference, while the chemical shift of each PC is updated as the intensity-weighted average of the chemical shifts of all peaks in the same PC, which is warranted to be statistically more accurate. Accurate chemical shifts for each representative spectral feature will facilitate subsequent peak assignment and are essential for correct metabolite identification and result interpretation. The proposed method was demonstrated successfully on the spectra of six model mixtures consisting of seven typical metabolites, yielding correct matching of all known spectral features. The performance of GIPMA was also demonstrated on 2D 1H-13C HSQC spectra of 87 real extracts of 29 samples of five Dendrobium species. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) of the 87 matched and aligned spectra by GIPMA generates correct classification of the 29 samples into five groups. In summary, the proposed algorithm of GIPMA provided a practical peak matching and alignment method to facilitate 2D NMR-based metabolomics studies.

Total synthesis of (−)-ribesin B and its structural revision

A highly symmetric dihydrofuran lignan, ribesin B (1), isolated from the leaves of Ribes nigrum, was synthesized via a process whereby the key step was a sequential Michael addition–carbocyclization. However, the NMR spectral features of the synthesized 1 were inconsistent with those of the natural product 1. Thus, the chemical synthesis of the isovanillin-moiety containing compound 2 from chiral propargyl alcohol was conducted through a process that included lipase-catalyzed kinetic resolution. The NMR spectrum of 2 was perfectly superimposable to that of naturally isolated ribesin B. Consequently, the structure of ribesin B was revised to be that of 2.

Relativistic topological and spectral characteristics of zeolite SAS structures

Zeolite SAS is a novel microporous zeotype material known as magnesioaluminophosphate with small pores and large cavities. The framework morphology of SAS is an excellent choice for isomorphic substitution to incorporate various types of metal ions into its pores, offering it distinct acidic and redox characteristics. Zeolite SAS type materials are receiving significant attention due to diverse applications in catalysis, iron exchange, environmental remediation and gas separation. A recent study shows that the SAS type materials remove, reduce or retard the adsorption of toxins, especially in water. In order to explore the structural characteristics of zeolite SAS and enhance its possible applications in QSPR and QSAR investigations, we employ graph theoretical techniques to derive the exact analytical formula of Wiener, Szeged, Mostar and degree type topological indices, which contain various information on molecules that can be useful in describing the physicochemical and biological properties of the materials. Furthermore we obtain the vertex partitions and spectral characteristics which in turn can aid in the interpretation of ESR and NMR spectral features as well as in relative comparisons of structures and their stabilities.

NMR-Based Metabolomics to Evaluate Individual Response to Treatments.

The aim of this chapter is to highlight the various aspects of metabolomics in relation to health and diseases, starting from the definition of metabolic space and of how individuals tend to maintain their own position in this space. Physio-pathological stimuli may cause individuals to lose their position and then regain it, or move irreversibly to other positions. By way of examples, mostly selected from our own work using 1H NMR on biological fluids, we describe the effects on the individual metabolomic fingerprint of mild external interventions, such as diet or probiotic administration. Then we move to pathologies (such as celiac disease, various types of cancer, viral infections, and other diseases), each characterized by a well-defined metabolomic fingerprint. We describe the effects of drugs on the disease fingerprint and on its reversal to a healthy metabolomic status. Drug toxicity can be also monitored by metabolomics. We also show how the individual metabolomic fingerprint at the onset of a disease may discriminate responders from non-responders to a given drug, or how it may be prognostic of e.g., cancer recurrence after many years. In parallel with fingerprinting, profiling (i.e., the identification and quantification of many metabolites and, in the case of selected biofluids, of the lipoprotein components that contribute to the 1H NMR spectral features) can provide hints on the metabolic pathways that are altered by a disease and assess their restoration after treatment.

Comprehensive study of Anthriscus sylvestris lignans

Wild chervil (Anthriscus sylvestris) is a widespread, wild-growing herbaceous plant from Apiaceae family, known for high content of lignans related to podophyllotoxin, and thus representing a promising new source for their industrial isolation. The data on detailed chemical profile of A. sylvestris lignans are still lacking. By combining fractionation with non-targeted LC-DAD-ESI-MS/MS metabolite profiling, we have identified, fully or tentatively, 46 lignans, 12 of which were never reported in A. sylvestris and 19 in any biological source. The dominant lignans were found to be nemerosin, yatein, deoxypodophyllotoxin, podophyllotoxin, podophyllotoxone and guayadequiol. In addition to well-known dibenzylbutyrolactones, aryltetralins and 7-oxygenated aryltetralins, we found several oxygenated lignan classes previously undescribed in A. sylvestris – 7-hydroxy, 7-oxo and 8-hydroxydibenzylbutyrolactones, a 7′-oxotetrahydrofuran and a 7-hydroxyarylnaphthalene. To facilitate future rapid classification and identification of lignans in raw extracts, UV, MS and NMR spectral features of different lignan classes are described.

Dysregulated Alanine as a Potential Predictive Marker of Glioma-An Insight from Untargeted HRMAS-NMR and Machine Learning Data.

Metabolic alterations play a crucial role in glioma development and progression and can be detected even before the appearance of the fatal phenotype. We have compared the circulating metabolic fingerprints of glioma patients versus healthy controls, for the first time, in a quest to identify a panel of small, dysregulated metabolites with potential to serve as a predictive and/or diagnostic marker in the clinical settings. High-resolution magic angle spinning nuclear magnetic resonance spectroscopy (HRMAS-NMR) was used for untargeted metabolomics and data acquisition followed by a machine learning (ML) approach for the analyses of large metabolic datasets. Cross-validation of ML predicted NMR spectral features was done by statistical methods (Wilcoxon-test) using JMP-pro16 software. Alanine was identified as the most critical metabolite with potential to detect glioma with precision of 1.0, recall of 0.96, and F1 measure of 0.98. The top 10 metabolites identified for glioma detection included alanine, glutamine, valine, methionine, N-acetylaspartate (NAA), γ-aminobutyric acid (GABA), serine, α-glucose, lactate, and arginine. We achieved 100% accuracy for the detection of glioma using ML algorithms, extra tree classifier, and random forest, and 98% accuracy with logistic regression. Classification of glioma in low and high grades was done with 86% accuracy using logistic regression model, and with 83% and 79% accuracy using extra tree classifier and random forest, respectively. The predictive accuracy of our ML model is superior to any of the previously reported algorithms, used in tissue- or liquid biopsy-based metabolic studies. The identified top metabolites can be targeted to develop early diagnostic methods as well as to plan personalized treatment strategies.

Polysaccharides in Siraitia grosvenori flowers and herbal tea

Siraitia grosvenori fruits are used as a sweetener and in traditional medicine. Their composition is more frequently studied contrary to flowers or herbal tea made of this plant. Infusions or decoctions of S. grosvenori flowers and herbal tea, commercially available products for daily use, are ingested into our body in terms of herbal medicine with potentially health beneficial impact. Mogrosides are supposed to be responsible for biological activities of S. grosvenori; however, it is well known that polysaccharides can also exhibit interesting biological activities. Composition of purified polysaccharidic complex matrices, isolated from S. grosvenori flowers and herbal tea by infusion and decoction, was the target of our study performed mainly by GC–MS and NMR. Characteristic NMR spectral features allowed an identification of the arabinogalactan type II and acidic biopolymers, homogalacturonan and highly esterified homogalacturonan in infusions of the herbal tea and flower and decoction of flowers. In the decoction sample of herbal tea inulin was found as the dominant polysaccharide. Comparison of compositional and linkage analyses data with those of 2D NMR spectra allowed an identification of fine structural elements of arabinogalactan polymers.

Methodology for the Development of Empirical Models Relating 13C NMR Spectral Features to Fuel Properties

Effective formulation of new gasoline or diesel fuels for internal combustion engines would benefit from the development of reliable models for predicting key fuel properties based on a set of mole...

Correction: Support for instructional scaffolding with 1H NMR spectral features in organic chemistry textbook problems

Correction for ‘Support for instructional scaffolding with 1H NMR spectral features in organic chemistry textbook problems’ by Shannon Y. C. Anderson et al., Chem. Educ. Res. Pract., 2020, DOI: 10.1039/c9rp00252a.

Electronic active defects and local order in doped ZnO ceramics inferred from EPR and 27Al NMR investigations

Doped ZnO based ceramics were fabricated by using a solid state reaction of ZnO co-doped by TiO2, Al2O3 and MgO and sintered in different atmospheres (Air, N2, N2 + CO). The crystalline structures consist in wurtzite ZnO and a minor spinel phase Zn2TiO4. The electrical conductivity is modulated by the sintering conditions with the highest value (˜105 S m−1) obtained in the reducing atmosphere (N2 + CO). The role of defects and vacancies on the electrical behavior was exhaustively investigated by Raman, electron paramagnetic resonance (EPR) and solid state NMR methods. The paramagnetic centres inferred from EPR studies show a Pauli-like spin susceptibility. Their origin was assigned to shallow donors from interstitial defects (Zni) favored by substitutional Al ions (AlZn). The NMR spectral features with a characteristic 185 ppm line which correlates with the electrical conductivity are presumed to be caused by the Knight shift effect from the conduction electrons and the involved paramagnetic centres.

Ability of IR and NMR Spectral Data to Distinguish between a Tetrel Bond and a Hydrogen Bond.

The placement of a nucleophile X along the R-CH3 axis of a methyl group can be described as either a trifurcated H bond or as a tetrel bond between C and X. Quantum calculations of the vibrational and NMR spectral features of a number of systems are used to provide a framework by which to distinguish between the presence of a tetrel or H bond. Both cationic and neutral methyl-containing Lewis acids (SMe3+, NMe4+, SMe2) are paired with both neutral and anionic Lewis bases (NH3, OH2, OCHNH2, OCH3-, OH-, HCOO-). As the base is moved away from the R-CH3 axis of the Lewis acid (tetrel bond) toward a position along a CH axis (CH···X H bond), the methyl stretching frequencies shift to the red, and the bending modes shift to the blue. This modification in the geometry also causes the methyl C atom NMR chemical shielding to increase, while the methyl H atom is progressively deshielded. These changes are of sufficiently large magnitude that they should provide a means to distinguish these two bonding situations from one another.

Solid-State NMR Structural Characterization of Self-Assembled Peptides with Selective 13C and 15N Isotopic Labels.

For the structural characterization methods discussed here, information on molecular conformation and intermolecular organization within nanostructured peptide assemblies is discerned through analysis of solid-state NMR spectral features. This chapter reviews general NMR methodologies, requirements for sample preparation, and specific descriptions of key experiments. An attempt is made to explain choices of solid-state NMR experiments and interpretation of results in a way that is approachable to a nonspecialist. Measurements are designed to determine precise NMR peak positions and line widths, which are correlated with secondary structures, and probe nuclear spin-spin interactions that report on three-dimensional organization of atoms. The formulation of molecular structural models requires rationalization of data sets obtained from multiple NMR experiments on samples with carefully chosen 13C and 15N isotopic labels. The information content of solid-state NMR data has been illustrated mostly through the use of simulated data sets and references to recent structural work on amyloid fibril-forming peptides and designer self-assembling peptides.

Restricted amide rotation with steric hindrance induced multiple conformations

The CN bond character is dependent directly upon the resonance-contributor structure population driven by the delocalized nitrogen lone-pair of electrons. In the case of N, N-dibenzyl-ortho-toluamide (o-DBET), the molecule adopts subpopulations of conformers with distinct NMR spectral features, particularly at low temperatures. This conformational adaptation is unique to o-DBET, while the corresponding meta- and para- forms do not show such behavior. Variable-temperature (VT) NMR, two-dimensional exchange spectroscopy (EXSY), and qualitative molecular modeling studies are used to demonstrate how multiple competing interactions such as restricted amide rotation and steric hindrance effects can lead to versatile molecular adaptations in the solution state.

Plant Resources, (13)C-NMR Spectral Characteristic and Pharmacological Activities of Dammarane-Type Triterpenoids.

Dammarane-type triterpenoids (DTT) widely distribute in various medicinal plants. They have generated a great amount of interest in the field of new drug research and development. Generally, DTT are the main bioactive ingredients abundant in Araliaceae plants, such as Panax ginseng, P. japonicas, P. notoginseng, and P. quinquefolium. Aside from Araliaceae, DTT also distribute in other families, including Betulaceae, Cucurbitaceae, Meliaceae, Rhamnaceae, and Scrophulariaceae. Until now, about 136 species belonging to 46 families have been reported to contain DTT. In this article, the genus classifications of plant sources of the botanicals that contain DTT are reviewed, with particular focus on the NMR spectral features and pharmacological activities based on literature reports, which may be benefit for the development of new drugs or food additives.

Structural and NMR Spectroscopic Investigations of CuI, CuII, NiII, ZnII and FeII Complexes of 2, 9‐Di‐(Benzothiazolino)‐1,10‐Phenanthroline

AbstractSynthesis and characterisation of a disubstituted phenanthroline, “dbt‐phen” (“dbt‐phen”, 2,9‐di(benzothiazolino)‐1,10‐phenanthroline) 1 and its CuI, CuII, NiII, ZnII and FeII complexes are reported. Three different coordination modes of the ligand viz., bis(didentate), tridentate and tetradentate are observed. Under various experimental conditions, 1 forms a double‐stranded dicopper(I)helicate, [CuI2(dbt‐phen)2]2+ 2; a mono(dbt‐phen) copper(II) complex, [CuII(dbt‐phen)(H2O)2]2+ 3, a NiII complex [Ni(dbt‐ phen)(NCMe)2(OH2)]2+ 4, a bis(dbt‐phen) zinc(II) complex, [ZnII(dbt‐phen)2]2+ 5 and a pseudo‐octahedral complex [FeII(dbt‐phen)Br2] 6. Crystal packing feature of the dicopper helicate [CuI(dbt‐phen)]2[BF4]2, 2+[BF4]2 reveals novel short contacts between BF4− ions and the hydrogens of the phenyl rings leading to the peculiar double stranded and helical topology. The complex [CuII(dbt‐phen)(OH2)2(ClO4)][ClO4], 3+[ClO4] exhibits both intra‐ and inter‐molecular H‐bonding interactions. 1H NMR spectral features of the ligand, copper(I) and zinc(II) complexes indicate that the free ligand and the copper(I) complex retain their solid state structures whereas the zinc(II) complex undergoes structural changes in solution.

A Novel MHC-I Surface Targeted for Binding by the MCMV m06 Immunoevasin Revealed by Solution NMR

As part of its strategy to evade detection by the host immune system, murine cytomegalovirus (MCMV) encodes three proteins that modulate cell surface expression of major histocompatibility complex class I (MHC-I) molecules: the MHC-I homolog m152/gp40 as well as the m02-m16 family members m04/gp34 and m06/gp48. Previous studies of the m04 protein revealed a divergent Ig-like fold that is unique to immunoevasins of the m02-m16 family. Here, we engineer and characterize recombinant m06 and investigate its interactions with full-length and truncated forms of the MHC-I molecule H2-L(d) by several techniques. Furthermore, we employ solution NMR to map the interaction footprint of the m06 protein on MHC-I, taking advantage of a truncated H2-L(d), "mini-H2-L(d)," consisting of only the α1α2 platform domain. Mini-H2-L(d) refolded in vitro with a high affinity peptide yields a molecule that shows outstanding NMR spectral features, permitting complete backbone assignments. These NMR-based studies reveal that m06 binds tightly to a discrete site located under the peptide-binding platform that partially overlaps with the β2-microglobulin interface on the MHC-I heavy chain, consistent with in vitro binding experiments showing significantly reduced complex formation between m06 and β2-microglobulin-associated MHC-I. Moreover, we carry out NMR relaxation experiments to characterize the picosecond-nanosecond dynamics of the free mini-H2-L(d) MHC-I molecule, revealing that the site of interaction is highly ordered. This study provides insight into the mechanism of the interaction of m06 with MHC-I, suggesting a structural manipulation of the target MHC-I molecule at an early stage of the peptide-loading pathway.

토양 휴민(Humin)의 분자구조 특성과 Phenanthrene 흡착상수와의 상관관계에 대한 연구

In this study, sorption coefficients (logKOC, n) for the binding of phenanthrene (PHE) to soil humins, insoluble fraction of soil humc substances (HS), were determined and relationship between the sorption coefficients and structural characteristics of the soil humins were investigated. The soil humins used in the present study were isolated from 7 different soils including 5 domestic soils, an IHSS standard and a peat soil, and characterized by elemental analysis and CPMAS C NMR method. C NMR spectral features indicate that the soil humins are mainly made up of aliphatic carbons (57.1~72.3% in total carbon) with high alkyl-C moiety, and the alkyl-C contents (CAl-H,C, %) was in order of granite soil Hu (26~42%) > volcanic ash soil, HL Hu (23.9%) > Peat Hu (14.0%). The results of correlation study show that a positive relationship (r = 0.77, p < 0.05) between organic carbon normalized-sorption coefficients (KOC, mL/g) and alkyl-C contents(CAl-H,C, %), while negative relationship (r = (-)0.74, p < 0.05) between Freundlich sorption parameter (n) and H,C-substituted aromatic carbon contents (CAr-H,C, %). The magnitude of KOC values are also negatively well correlated with polarity index (e.g., PI, N + O)/C) (r = (-)0.74, p < 0.1). These results suggest that the binding capacity (e.g., KOC) for PHE is increased in soil humin molecules having high contents of alkyl-C or lower polarity, and nonlinear sorption for PHE increased as the H,C-substituted aromatic carbon contents (CAr-H,C, %) in the soil humins increased. The PHE sorption characteristics on soil humins are discussed based on the dual reactive mode of sorption model.

Metabolomic Analysis Reveals Extended Metabolic Consequences of Marginal Vitamin B-6 Deficiency in Healthy Human Subjects

Marginal deficiency of vitamin B-6 is common among segments of the population worldwide. Because pyridoxal 5′-phosphate (PLP) serves as a coenzyme in the metabolism of amino acids, carbohydrates, organic acids, and neurotransmitters, as well as in aspects of one-carbon metabolism, vitamin B-6 deficiency could have many effects. Healthy men and women (age: 20-40 y; n = 23) were fed a 2-day controlled, nutritionally adequate diet followed by a 28-day low-vitamin B-6 diet (<0.5 mg/d) to induce marginal deficiency, as reflected by a decline of plasma PLP from 52.6±14.1 (mean ± SD) to 21.5±4.6 nmol/L (P<0.0001) and increased cystathionine from 131±65 to 199±56 nmol/L (P<0.001). Fasting plasma samples obtained before and after vitamin B6 restriction were analyzed by 1H-NMR with and without filtration and by targeted quantitative analysis by mass spectrometry (MS). Multilevel partial least squares-discriminant analysis and S-plots of NMR spectra showed that NMR is effective in classifying samples according to vitamin B-6 status and identified discriminating features. NMR spectral features of selected metabolites indicated that vitamin B-6 restriction significantly increased the ratios of glutamine/glutamate and 2-oxoglutarate/glutamate (P<0.001) and tended to increase concentrations of acetate, pyruvate, and trimethylamine-N-oxide (adjusted P<0.05). Tandem MS showed significantly greater plasma proline after vitamin B-6 restriction (adjusted P<0.05), but there were no effects on the profile of 14 other amino acids and 45 acylcarnitines. These findings demonstrate that marginal vitamin B-6 deficiency has widespread metabolic perturbations and illustrate the utility of metabolomics in evaluating complex effects of altered vitamin B-6 intake.

Anisotropic Spin-Fluctuations in SmCoPO Revealed by 31P NMR Measurement

31 P NMR spectral features in polycrystalline SmCoPO reveal an axially symmetric local magnetic field. At low temperature, the anisotropy of the internal magnetic field increases rapidly, with K a b increasing faster than that of K c . The dominant contribution to this anisotropy arises from Sm-4 f electron contribution over that of Co-3 d . The intrinsic width 2β deviates from linearity with respect to bulk susceptibility below 170 K due to the enhancement of (1/ T 2 ) dynamic , which along with the continuous increase of anisotropy in the internal magnetic field is responsible for the wipe out effect of the NMR signal, well above T C . 1/ T 1 shows large anisotropy confirming a significant contribution of Sm-4 f electron spin fluctuations to 1/ T 1 , arising from indirect RKKY type exchange interaction indicating a non-negligible hybridization between Sm-4 f orbitals and the conduction band, over the itinerant character of the Co-3 d spins. This anisotropy originates from the orientation dependence of χ ′′ ( q ,ω). The 3 d -spin fluctuations in the a b -plane is 2D FM in nature, while along the c -axis, a signature of a weak AFM spin fluctuations superimposed on weak FM spin-fluctuations even in a field of 7 T and far above T N is observed. The enhancement of this AFM fluctuations of the Co-3 d spins along c -axis, at further low temperature is responsible to drive the system to an AFM ordered state.