Chemical Correlation Research Articles

Chemical Perturbation Two-Dimensional Correlation Ultraviolet Visible Spectroscopy for Quality Control of Chinese Liquor

ABSTRACTIn this work, a new method of two-dimensional correlation ultraviolet visible spectroscopy of Chinese liquor system was constructed with chemical reaction as an external perturbation. It has the advantages of easy to implement, simple operation, and abundant spectral signals. Using the Hai-Zhi-Lan liquor as the main research sample, this study found that the two-dimensional correlation ultraviolet visible spectrum of Hai-Zhi-Lan liquor exhibited two auto peaks and six cross peaks. Quantitative analysis using the correlation coefficient method showed that there were high correlations among different batches of Hai-Zhi-Lan liquor (≥0.99). Furthermore, the two-dimensional correlation ultraviolet visible spectra of Tian-Zhi-Lan liquor and Meng-Zhi-Lan liquor were obtained under the same conditions, which were produced in the same factory as Hai-Zhi-Lan liquor (Yang-He Company). The results showed that these liquors from the same manufacturer have certain correlations, but there were also differences in spectral intensities and regions, and, as a result, the correlation coefficients showed a downward trend. Finally, the two-dimensional correlation ultraviolet visible spectra of different brands of Chinese liquor produced by other manufactures were investigated and compared with the Hai-Zhi-Lan liquor. The results showed that there were some differences among the liquors, and the correlation coefficients were lower. Hence, through the use of the two-dimensional correlation ultraviolet visible spectroscopy, the characteristics of Chinese liquor can be obtained in three-dimensional space. This method can be applied to brand discrimination of quality control of Chinese liquor with high potential application value. Additionally, this strategy can provide a reference for quality discrimination research of other food systems.

Real-time homonuclear broadband decoupled pure shift COSY.

The present manuscript reports development and applications of real-time homonuclear broadband decoupled pure shift version of in-phase zero-quantum filtered COSY (PS-IPZF-COSY) and clean in-phase COSY (PS-CLIP-COSY) pulse schemes. In contrast to the conventional COSY schemes, these pure shift versions provide enhanced spectral resolution and simplify the chemical shift correlation analysis of scalar coupled spins in complex organic molecules, which are exemplified for erythromycin A, estradiol, and a mixture of estradiol and testosterone.

Coordinated Network Changes Across the Catalytic Cycle of Alpha Tryptophan Synthase

Networks of noncovalent interactions play important roles in the structural dynamics of globular proteins. Allosteric signals can propagate from the surface of an enzyme into its active site through these amino acid interaction networks. We used nuclear magnetic resonance chemical shift covariance analyses on a catalytically inactive variant of the alpha subunit of tryptophan synthase to map its amino acid interaction networks across its entire catalytic cycle. Each enzyme intermediate has unique sets of residues that display high chemical shift correlations across a set of alanine-to-glycine loop substitutions. Moreover, these chemical shift correlations systematically increase or decrease as a function of the catalytic cycle. These studies indicate that the enzyme intermediates have different amino acid interaction networks, and these network transitions are likely important for catalytic cycle progression. The different network interactions likely help to position catalytic machinery and coordinate function with the beta subunit.

Regional feature extraction of various fishes based on chemical and microbial variable selection using machine learning

We introduce a method for extracting regional and habitat features of various fish species based on chemical and microbial correlations that incorporate integrated analysis and a variable selection approach.

Spin-echo based diagonal peak suppression in solid-state MAS NMR homonuclear chemical shift correlation spectra

The feasibility of using the spin-echo based diagonal peak suppression method in solid-state MAS NMR homonuclear chemical shift correlation experiments is demonstrated. A complete phase cycling is designed in such a way that in the indirect dimension only the spin diffused signals are evolved, while all signals not involved in polarization transfer are refocused for cancellation. A data processing procedure is further introduced to reconstruct this acquired spectrum into a conventional two-dimensional homonuclear chemical shift correlation spectrum. A uniformly 13C, 15N labeled Fmoc-valine sample and the transmembrane domain of a human protein, LR11 (sorLA), in native Escherichia coli membranes have been used to illustrate the capability of the proposed method in comparison with standard 13C–13C chemical shift correlation experiments.

Comparison of 66 chemical element contents in normal and benign hyperplastic prostate

ObjectiveThe aim of this study was to clarify the differences between the prostatic levels of chemical elements in patients with benign prostatic hyperplasia (BPH) and healthy male. MethodsWe evaluated the prostatic level of 66 chemical elements in 43 patients with BPH and 37 healthy males. Measurements were performed using five instrumental analytical methods. ResultsIn the hyperplastic prostates, we have observed a significant increase in the mean level of Bi, Cr, Hg, K, Sb, and Se accompanied a significant decrease in the mean level of Al, Ce, Cs, Dy, Er, Gd, Ho, La, Mo, Nd, Pb, Pr, Sm, Sn, Tb, Tm, U, and Y. No differences were found in the mean prostatic level of other chemical elements including Ag, Al, Au, B, Ba, Be, Br, Ca, Cd, Co, Cu, Fe, Li, Mg, Mn, Na, Nb, Ni, P, Rb, S, Sc, Si, Th, Ti, Tl, Yb, Zn, and Zr between BPH patients and healthy males. ConclusionsThe finding of chemical element contents and correlation between pairs of chemical element mass fractions indicates that there is a great disturbance of prostatic chemical element metabolism in BPH gland. Trace elements Bi, Cr, Hg, K, Sb, and Se may be regarded as the possible tissue biomarkers of hyperplastic transformation of prostate gland. Obtained data did not confirm a critical role of Cd and Pb accumulation in the pathogenesis of BPH. A potential age-related Zn, Fe, and Se deficiency in the prostate tissue has not been found as being involved in the etiology of BPH.

Complete NMR Assignment of Succinimide and Its Detection and Quantification in Peptides and Intact Proteins.

Detecting and quantifying post-translational modifications (PTMs) in full-length proteins is a challenge, especially in the case of spontaneously occurring, nonenzymatic PTMs. Such a PTM is the formation of succinimide (Snn) in a protein that occurs spontaneously in prone primary sequences and leads typically to an equilibrium between Snn and its hydrolysis products isoaspartate (isoAsp) and aspartate. In order to detect these modifications in proteins by NMR spectroscopy, chemical shift assignments of reference compounds are required. We used peptide synthesis and 2D NMR spectroscopy to assign all 1H and 13C chemical shifts of Snn and isoAsp and found characteristic chemical shift correlations. To provide chemical shift reference data suitable for comparison with data of denatured proteins, we repeated the assignment in 7 M urea (pH 2.3) and in DMSO. Most characteristic of Snn are the two downfield shifted carbonyl chemical shifts, the chemical shift correlations of Cβ-Hβ of Snn and Cα-Hα of the succeeding residue which are clearly distinct from random coil chemical shift correlations. The characteristic 2D NMR fingerprints of Snn were used to detect and quantify this PTM in the model protein lysozyme, the biotherapeutic filgrastim, and the Fc part of immunoglobulin G1. Mass spectrometry (MS) was applied as an additional independent method. The orthogonality of the NMR and MS techniques allows cross-validation, which is especially important to search for subtle PTMs in proteins. Studying PTMs by NMR spectroscopy is a promising method to analyze proteins and peptides from natural sources, recombinant expression, or chemical synthesis.

The PROSECCO server for chemical shift predictions in ordered and disordered proteins

The chemical shifts measured in solution-state and solid-state nuclear magnetic resonance (NMR) are powerful probes of the structure and dynamics of protein molecules. The exploitation of chemical shifts requires methods to correlate these data with the protein structures and sequences. We present here an approach to calculate accurate chemical shifts in both ordered and disordered proteins using exclusively the information contained in their sequences. Our sequence-based approach, protein sequences and chemical shift correlations (PROSECCO), achieves the accuracy of the most advanced structure-based methods in the characterization of chemical shifts of folded proteins and improves the state of the art in the study of disordered proteins. Our analyses revealed fundamental insights on the structural information carried by NMR chemical shifts of structured and unstructured protein states.

A Nitrile Glucoside and Biflavones from the Leaves of Campylospermum excavatum (Ochnaceae).

The study of the MeOH extract of the leaves of Campylospermum excavatum led to the isolation of a nitrile glucoside, named campyloside C (1) and an original derivative of ochnaflavone, 7-O-methylochnaflavone (2), along with three known biflavonoids, amentoflavone, sequoiaflavone, and sotetsuflavone (3 - 5). The linkage site of the sub-units of 2 was confirmed by chemical correlation, after semi-synthesis of a trimethoxylated derivative of ochnaflavone (2a). The structures of these compounds as well as their relative and absolute configurations were assigned by 1D- and 2D-NMR experiments, HR-ESI-MS and Electronic Circular Dichroism (ECD) calculations. A low-pass J filter HMBC experiment was performed in order to define the configuration of the double bond of 1. All of the biflavonoids were evaluated against protozoan parasites. Amentoflavone moderately inhibited the promastigote form of Leishmania infantum.

Nucleophilic additions on acetyldioxanes derived from (−)-(1R)-myrtenal used as chiral auxiliaries: substituent effects on the stereochemical outcome

The synthesis of acetyldioxanes 4 and 9a starting from (−)-(1R)-myrtenal is described. The products were treated with a representative series of nucleophilic reagents (RMgX, RLi, NaBH4 and LiAlH4) to assess the effect of the substituent at C-3 on the stereochemical outcome. It was observed that the nucleophiles preferred the re-face of the CO group when the equatorial substituent at C-3 was a methyl group, whereas a phenyl group at the same position induced the addition through the si-face, thus allowing access to either desired stereochemistry of a final product. This behavior suggests that the formation of the expected Cram-chelated coordination complex takes a coplanar orientation with the C-3 equatorial substituent. Moreover, Grignard reagents were the most stereoselective nucleophiles. The stereochemistry of the addition was established by X-ray diffraction and chemical correlation.

Lipase‐Catalyzed Kinetic Resolution of N‐Substituted 1‐(β‐Hydroxypropyl)indoles by Enantioselective Acetylation

A new, concise, and efficient route towards both antipodes of N‐(β‐hydroxypropyl)indoles is described. The key step is an enantioselective lipase‐mediated acetylation of racemic indolic alcohols [1‐(1H‐indol‐1‐yl)propan‐2‐ol, 1‐(2‐methyl‐1H‐indol‐1‐yl)propan‐2‐ol, and 1‐(5‐bromo‐1H‐indol‐1‐yl)propan‐2‐ol] with enol esters (vinyl acetate and isopropenyl acetate) as acyl group donors, performed under kinetically controlled conditions. A substantial influence of enzyme type, acyl group donor, and organic solvent on conversion rates and enantioselectivity of the enzymatic kinetic resolutions (EKRs) of the respective racemates was examined in detail. The best results in terms of enantioselectivity were obtained for the resolutions performed with native lipase from Pseudomonas fluorescens (PFL, Amano AK) in diisopropyl ether (DIPE) or tert‐butyl methyl ether (TBME) solution. To support the assignment of the absolute configurations of EKR products, chemical correlations with enantiomerically enriched analytical standards and single‐crystal X‐ray diffraction analysis were applied.

Anomalous random correlations of force constants on the lattice dynamical properties of disordered Au-Fe alloys

Au-Fe alloys are of immense interest due to their biocompatibility, anomalous hall conductivity, and applications in various medical treatment. However, irrespective of the method of preparation, they often exhibit a high-level of disorder, with properties sensitive to the thermal or magnetic annealing temperatures. We calculate lattice dynamical properties of Au$_{1-x}$Fe$_x$ alloys using density functional theory methods, where, being a multisite property, reliable interatomic force constant (IFC) calculations in disordered alloys remain a challenge. We follow a two fold approach: (1) an accurate IFC calculation in an environment with nominally zero chemical pair correlations to mimic the homogeneously disordered alloy; and (2) a configurational averaging for the desired phonon properties (e.g., dispersion, density of states, and entropy). We find an anomalous change in the IFC's and phonon dispersion (split bands) near $x$=0.19, which is attributed to the local stiffening of the Au-Au bonds when Au is in the vicinity of Fe. Other results based on mechanical and thermo-physical properties reflect a similar anomaly: Phonon entropy, e.g., becomes negative below $x$=0.19, suggesting a tendency for chemical unmixing, reflecting the onset of miscibility gap in the phase diagram. Our results match fairly well with reported data, wherever available.

Graphene-carbon nanofiber hybrid supported Pt nanoparticles with enhanced catalytic performance for methanol oxidation and oxygen reduction

Graphene-embedded carbon fiber (RGO-CF) and graphene/carbon fiber hybrid (RGO/CF) are prepared and used as supports of Pt nanoparticles for electrocatalysis applications. The chemical structure-activity correlations of the obtained electrocatalysts are investigated and compared with the commercial catalyst–Pt/C. The Pt nanoparticles loaded on RGO/CF exhibits increased catalytic stability in both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). Furthermore, the activity for ORR increases. Series of characterization results reveal that the remarkable electrocatalytic performance of Pt/RGO/CF is rooted in that RGO/CF support offers abundant graphitic-N and oxygen functional groups, low charge transfer resistance, as well as the strong interaction between Pt nanoparticles and RGO/CF. These results indicate that RGO/CF can be a promising support for the improvement of electrochemical activity and stability of fuel cell.

Characterization of some archaeological ceramics and clay samples from Zamala - Far-northern part of Cameroon (West Central Africa)

Abstract Seventeen ceramics samples (515±95 BP, about 580 years old) and two clay raw materials from Zamala (Far-northern, Cameroon) were characterized by X-ray diffraction (XRD), thermal analysis (DTA/TG) and X-ray fluorescence spectroscopy. The aim of the work was the deduction of the production technology and provenance of these ceramics. With the exception of one sample the analysed ceramics formed a homogeneous chemical and mineralogical group. The observed mineralogical phases were quartz, mica (biotite), potassium feldspar (microcline) and plagioclase (albite and oligoclase). The XRD study of two local clays yielded the presence of quartz, kaolinite, mica, feldspar and plagioclase. The presence of the broad endothermic peak in the DTA/TG curves of the clays and its absence in the curves of the ceramics indicated that the firing temperature of the ceramics was above 550-600 °C, which is the temperature of the kaolinite-metakaolinite transformation. The firing experiments of the clay between 400-1200 °C in oxidizing atmosphere showed that mica disappeared above 900 °C. Therefore, the firing temperature of the sherds should have been between 600-900 °C. The chemical correlation between ceramics and local clay materials pointed out to a local production of these ceramics.

Quantum criticality of bosonic systems with the Lifshitz dispersion

We study the quantum criticality of the Lifshitz $\varphi^4$-theory below the upper critical dimension. Two fixed points, one Gaussian and the other non-Gaussian, are identified with zero and finite interaction strengths, respectively. At zero temperature the particle density exhibits different power-law dependences on the chemical potential in the weak and strong interaction regions. At finite temperatures, critical behaviors in the quantum disordered region are mainly controlled by the chemical potential. In contrast, in the quantum critical region critical scalings are determined by temperature. The scaling ansatz remains valid in the strong interaction limit for the chemical potential, correlation length, and particle density, while it breaks down in the weak interaction one. As approaching the upper critical dimension, physical quantities develop logarithmic dependence on dimensionality in the strong interaction region. These results are applied to spin-orbit coupled bosonic systems, leading to predictions testable by future experiments.

Glucuronide and Sulfate Conjugates of Bisphenol A: Chemical Synthesis and Correlation Between Their Urinary Levels and Plasma Bisphenol A Content in Voluntary Human Donors.

Bisphenol A (BPA) glucuronide and sulfate conjugates are major products of Phase II metabolism of BPA in humans. In the past, their determination in body fluids usually involves tedious enzymatic hydrolysis and multiresidual analysis. The recent availability of authentic standards of these conjugates enables our better understand of the human metabolism of BPA and the distribution of their metabolites in body fluids. In this work, we report the chemical synthesis and purification of BPA mono- and di-glucuronide and BPA mono- and di-sulfate. Their levels, as well as that of BPA, in 140 paired human plasma and urine samples collected randomly from voluntary donors in Hong Kong SAR, China, were determined by solid-phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS). BPA was found in more than 135 human plasma and urine samples. Its Phase II metabolites, ranging from N.D. to 36.7µgg-1-creatinine, also were detected in 139 of the 140 urine samples. Good correlation (r=0.911) between molar concentration of BPA in the plasma and that of "total urinary BPA" (i.e., ln [(BPA+∑ BPA phase II conjugate)molar concentration]) was observed. Direct quantification of Phase II metabolites of BPA in human urine can be a useful assessment tool for population exposure to this potent endocrine disrupting chemical.

Exploring the Sponge Consortium Plakortis symbiotica-Xestospongia deweerdtae as a Potential Source of Antimicrobial Compounds and Probing the Pharmacophore for Antituberculosis Activity of Smenothiazole A by Diverted Total Synthesis.

Fractionation of the bioactive CHCl3-MeOH (1:1) extracts obtained from two collections of the sponge consortium Plakortis symbiotica-Xestospongia deweerdtae from Puerto Rico provided two new plakinidone analogues, designated as plakinidone B (2) and plakinidone C (3), as well as the known plakinidone (1), plakortolide F (4), and smenothiazole A (5). The structures of 1-5 were characterized on the basis of 1D and 2D NMR spectroscopic, IR, UV, and HRMS analysis. The absolute configurations of plakinidones 2 and 3 were established through chemical correlation methods, VCD/ECD experiments, and spectroscopic data comparisons. When assayed in vitro against Mycobacterium tuberculosis H37Rv, none of the plakinidones 1-3 displayed significant activity, whereas smenothiazole A (5) was the most active compound, exhibiting an MIC value of 4.1 μg/mL. Synthesis and subsequent biological screening of 8, a dechlorinated version of smenothiazole A, revealed that the chlorine atom in 5 is indispensable for anti-TB activity.

Lanostane triterpenoids from cultivated fruiting bodies of the basidiomycete Ganoderma orbiforme

A new 3,4-seco-27-norlanostane triterpene, ganoboninketal D (1), a new lanostane, (24S)-3-oxo-7α,24,25-trihydroxylanosta-8-ene (2), together with six known lanostanes (3–8), were isolated from cultivated fruiting bodies of the basidiomycete Ganoderma orbiforme. The structures were elucidated on the basis of NMR spectroscopic and mass spectrometry data, and the structures 1 and 2 were further confirmed by chemical correlations to ganoboninketal C and ganodermanondiol, respectively. All isolated compounds were inactive in the antitubercular and antimalarial activity assays against Mycobacterium tuberculosis H37Ra and Plasmodium falciparum K1, respectively, except that compound 8 exhibited weak antitubercular activity (MIC 50μg/ml).

Spectral Classification of One‐Dimensional Binary Aperiodic Crystals: An Algebraic Approach

AbstractA spectral classification of general one‐dimensional binary aperiodic crystals (BACs) based on both their diffraction patterns and energy spectrum measures is introduced along with a systematic comparison of the zeroth‐order energy spectrum main features for BACs belonging to different spectral classes, including Fibonacci‐class, precious means, metallic means, mixed means and period doubling based representatives. These systems are described by means of mixed‐type Hamiltonians which include both diagonal and off‐diagonal terms aperiodically distributed. An algebraic approach highlighting chemical correlation effects present in the underlying lattice is introduced. Close analytical expressions are obtained by exploiting some algebraic properties of suitable blocking schemes preserving the atomic order of the original lattice. The existence of a resonance energy which defines the basic anatomy of the zeroth‐order energy spectra structure for the standard Fibonacci, the precious means and the Fibonacci‐class quasicrystals is disclosed. This eigenstate is also found in the energy spectra of BACs belonging to other spectral classes, but for specific particular choices of the corresponding model parameters only. The transmission coefficient of these resonant states is always bounded below, although their related Landauer conductance values may range from highly conductive to highly resistive ones, depending on the relative strength of the chemical bonds.

Kinematic trends in young and old stars

AbstractUsing RAVE DR5, we explore the age, kinematic, and chemical correlations of a sample of 30,000 FGK stars. We separate a sample of turnoff stars into two age groups: young and old. For each of the two age groups, we calculate kinematic trends as a function of Galactocentric radius (R), for different metallicity ([Fe/H]) bins. For both young and old stars, we measure a negative gradient in ∂〈VR〉/∂R. In addition, for young stars we find a correlation between the magnitude of the slope and metallicity, with the most metal-rich bins having the steepest gradient and the most metal-poor bins having a flatter trend.