¹⁷O Quadrupole Coupling and Chemical Shielding Tensors in an H-bonded Carboxyl Group: α-Oxalic Acid

We have used single crystal 17O NMR and density functional theory to investigate intermolecular interactions in a strongly H-bonded system. The chemical shielding (CS) and quadrupole coupling (QC) tensors are determined in oxalic acid dihydrate by single crystal methods. With cross polarization from abundant protons, high quality spectra are obtained in 1−2 min from 10 μmol samples. In the crystal lattice, oxalic acid is H-bonded directly to the hydrate with each carboxyl group accepting two H-bonds at CO and donating one H-bond from COH. The effects of these intermolecular interactions on the experimentally determined QC and CS tensors are modeled by density functional theory with a procedure that accurately calculates, without scaling, the known QC tensors in both gas-phase water and ice. The ice calculation uses a cluster containing 42 waters (in excess of two complete hydration shells). The same procedure applied to a similarly constructed cluster of hydrated oxalic acid gives QC and CS tensors that are within 3−6% of the observed values while isolated molecule tensors are significantly different. Comparison of the isolated molecule tensors with those from either experiment or the cluster calculation shows the magnitude and directionality of intermolecular interactions on the tensors. The isotropic shift of the COH oxygen is deshielded by 29 ppm, and CO is shielded by 62 ppm while the spans of the CS tensors are increased by 78 ppm and decreased by 73 ppm, respectively. Magnitudes of the quadrupole coupling constants, which are proportional to the electric field gradients at the 17O sites, decrease by 2.2 and 1.2 MHz at COH and CO, respectively

Experiential Avoidance Mediates the Association between Emotion Regulation Abilities and Loneliness

<div><p>Experiential avoidance (EA) involves the unwillingness to remain in contact with aversive experiences such as painful feelings, thoughts, and emotions. EA is often associated with the development and maintenance of emotional problems. Since loneliness is characterized by negative emotions such as sadness and pessimism, which is often linked to emotional problems, this study aims to test the mediating effects of EA on the relationship between emotion regulation abilities (ERA) and loneliness in a sample of Chinese adults. Five hundred undergraduates completed questionnaires measuring EA (Acceptance and Action Questionnaire; AAQ-Ⅱ), ERA (Failure-relate action orientation; Action Control Scale, ACS-90) and loneliness (UCLA Loneliness Scale). Structural equation modeling showed that EA fully-mediated the relationship between ERA and loneliness. The findings suggest EA is a key mechanism in explaining why people with high ERA are prone to feeling lower levels of loneliness. In particular, these findings have important implications for designing effective psychological interventions for loneliness.</p></div

Final structural model (n = 500, standardized path coefficients).

<p><i>Note</i>: <i>ERA</i> = emotion regulation abilities; <i>EA</i> = experiential avoidance; <i>L</i> = loneliness (<i>L1–L4</i> four parcels of loneliness). *<i>p</i><0.05; **<i>p</i><0.01.</p

Direct and indirect effects and 95% confidence intervals for the mediation model.

<p>Direct and indirect effects and 95% confidence intervals for the mediation model.</p

Correlations, means, and standard deviations for study variables.

<p>Correlations, means, and standard deviations for study variables.</p

Supplementary Data from A Novel mTORC1/2 Inhibitor (MTI-31) Inhibits Tumor Growth, Epithelial–Mesenchymal Transition, Metastases, and Improves Antitumor Immunity in Preclinical Models of Lung Cancer

Supplement data</p

Additional file 1 of Genomic and functional characterization of carbapenem-resistant Klebsiella pneumoniae from hospital wastewater

Additional file 1: Table S1.Main microbiological characteristics of 11 clinical CRKP isolates. Table S2. AntimicrobialSusceptibility Testing of 11 clinical CRKP isolates. Table S3. Nucleotide sequences ofprimers used in this study

Image_1_Screening Tea Cultivars for Novel Climates: Plant Growth and Leaf Quality of Camellia sinensis Cultivars Grown in Mississippi, United States.tif

The United States (U.S.) consumed over 80 billion servings of tea, approximately 3.8 billion gallons, in the year of 2018. With the vast majority of tea demand being met by importation, the United States became the third largest tea importer worldwide after Russia and Pakistan. As demand for domestically produced tea increases and growers expressing increasing interest in growing and producing tea, tea production became an emerging industry in the United States. Compared to major tea producing countries with centuries of growing history, tea production in the United States is limited and requires research support in many aspect of tea production including selecting suitable cultivars adapted to local climatic conditions. This study evaluated nine tea cultivars, including ‘BL1,’ ‘BL2,’ ‘Black Sea,’ ‘Christine’s Choice,’ ‘Dave’s Fave,’ ‘Large Leaf,’ ‘Small Leaf,’ ‘Sochi,’ and ‘var. assamica,’ for plant growth, leaf morphological characteristics, cold tolerance, and leaf biochemical compositions when grown in Mississippi United States with a subtropical climate. The nine tested cultivars had varying plant growth indices (PGI) and varying degrees of cold tolerance to freezing temperatures in winter, but resumed healthy growth the following spring. ‘BL2’ showed the highest PGI of 104.53 cm by February 2019, which might be helpful toward suppressing weed and early establishment of tea plantation. The nine cultivars also showed varying leaf characteristics in terms of leaf length, width, area, fresh and dry weights, and new shoot weight. There existed a diversity in leaf biochemical composition including soluble solids, carbohydrates, total polyphenols (TP), free amino acids (AA), L-theanine and caffeine among the nine cultivars and among different harvesting seasons of spring, summer, and fall within a certain cultivar. The nine cultivars in this study generally grow well in local environment. All tea samples collected from nine cultivars and three seasons were considered suitable for green tea processing with low TP/AA ratios ranging from 1.72 to 3.71 in this study.</p

¹⁵N Chemical Shielding in Glycyl Tripeptides: Measurement by Solid-State NMR and Correlation with X-ray Structure

15N chemical shielding parameters are reported for central glycyl residues in crystallographically characterized tripeptides with α-helix, β-strand, polyglycine II (31-helix), and extended structures. Accurate values of the shielding components (2−5 ppm) are determined from MAS and stationary spectra of peptides containing [2-13C,15N]Gly. Two dipolar couplings, 1H−15N and 13Cα−15N, are used to examine 15N shielding tensor orientations in the molecular frame and the results indicate that the δ11, δ33 plane of the shielding tensor is not coincident with the peptide plane. The observed isotropic shifts, which vary over a range of 13 ppm, depend on hydrogen bonding (direct and indirect) and local conformation. Tensor spans, δspan = δ11 − δ33, and their deviations from axial symmetry, δdev = δ22 − δ33, vary over a larger range and are grouped according to 2° structure. Augmented by previously reported 13Cα shielding parameters, a prediction scheme for the 2° structure of glycyl residues in proteins based on shielding parameters is proposed

¹⁵N Chemical Shielding in Glycyl Tripeptides: Measurement by Solid-State NMR and Correlation with X-ray Structure

15N chemical shielding parameters are reported for central glycyl residues in crystallographically characterized tripeptides with α-helix, β-strand, polyglycine II (31-helix), and extended structures. Accurate values of the shielding components (2−5 ppm) are determined from MAS and stationary spectra of peptides containing [2-13C,15N]Gly. Two dipolar couplings, 1H−15N and 13Cα−15N, are used to examine 15N shielding tensor orientations in the molecular frame and the results indicate that the δ11, δ33 plane of the shielding tensor is not coincident with the peptide plane. The observed isotropic shifts, which vary over a range of 13 ppm, depend on hydrogen bonding (direct and indirect) and local conformation. Tensor spans, δspan = δ11 − δ33, and their deviations from axial symmetry, δdev = δ22 − δ33, vary over a larger range and are grouped according to 2° structure. Augmented by previously reported 13Cα shielding parameters, a prediction scheme for the 2° structure of glycyl residues in proteins based on shielding parameters is proposed