A simple method of estimating homolytic bond dissociation energies (BDEs) in Me^O solution for H-A type substrates has been devised by combination of their equilibrium acidities, p£HA, and the oxidation potentials of their conjugate bases, £0X(A~), by using an equation derived from a thermodynamic cycle. For 9-methylanthracene, diphenylmethane, triphenylmethane, cyclopentadiene, indene, fluorene, acetone, thiophenol, phenol, and aniline reasonable agreement with gas-phase BDEs was obtained. The method has been extended to the benzylic C-H bonds in phenylacetonitrile, ethyl phenylacetate, and benzyl phenyl sulfone for which gas-phase BDEs do not appear to be available. The effects of CN, C02Et, and S02Ph groups on the C-H BDEs, relative to that in toluene in these three compounds, were found to correspond closely to the effects of CN, CQ2Me, and S02Ph groups on the 9-C-H BDEs in 9-substituted fluorenes, relative to that in fluorene.

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A Huisgen 1,3-dipolar cycloaddition "click chemistry" was employed to immobilize azido sugars (mannose, lactose, alpha-Gal) to fabricate carbohydrate self-assembled monolayers (SAMs) on gold. This fabrication was based on preformed SAM templates incorporated with alkyne terminal groups, which could further anchor the azido sugars to form well-packed, stable, and rigid sugar SAMs. The clicked mannose, lactose, and alpha-Gal trisaccharide SAMs were used in the analysis of specific carbohydrate-protein interactions (i.e., mannose-Con A; ECL-lactose, alpha-Gal-anti-Gal). The apparent affinity constant of Con A binding to mannose was (8.7 +/- 2.8) x 10(5) and (3.9 +/- 0.2) x 10(6) M(-1) measured by QCM and SPR, respectively. The apparent affinity constants of lactose binding with ECL and alpha-Gal binding with polyclonal anti-Gal antibody were determined to be (4.6 +/- 2.4) x 10(6) and (6.7 +/- 3.3) x 10(6) M(-1), respectively by QCM. SPR, QCM, AFM, and electrochemistry studies confirmed that the carbohydrate SAM sensors maintained the specificity to their corresponding lectins and nonspecific adsorption on the clicked carbohydrate surface was negligible. This study showed that the clicked carbohydrate SAMs in concert with nonlabel QCM or SPR offered a potent platform for high-throughput characterization of carbohydrate-protein interactions. Such a combination should complement other methods such as ITC and ELISA in a favorable manner and provide insightful knowledge for the corresponding complex glycobiological processes.

Heterolytic and homolytic bond dissociation energies of the C4-H bonds in ten NADH models (seven 1,4-dihydronicotinamide derivatives, two Hantzsch 1,4-dihydropyridine derivatives, and 9,10-dihydroacridine) and their radical cations in acetonitrile were evaluated by titration calorimetry and electrochemistry, according to the four thermodynamic cycles constructed from the reactions of the NADH models with N,N,N',N'-tetramethyl-p-phenylenediamine radical cation perchlorate in acetonitrile (note: C9-H bond rather than C4-H bond for 9,10-dihydroacridine; however, unless specified, the C9-H bond will be described as a C4-H bond for convenience). The results show that the energetic scales of the heterolytic and homolytic bond dissociation energies of the C4-H bonds cover ranges of 64.2-81.1 and 67.9-73.7 kcal mol(-1) for the neutral NADH models, respectively, and the energetic scales of the heterolytic and homolytic bond dissociation energies of the (C4-H)(.+) bonds cover ranges of 4.1-9.7 and 31.4-43.5 kcal mol(-1) for the radical cations of the NADH models, respectively. Detailed comparison of the two sets of C4-H bond dissociation energies in 1-benzyl-1,4-dihydronicotinamide (BNAH), Hantzsch 1,4-dihydropyridine (HEH), and 9,10-dihydroacridine (AcrH(2)) (as the three most typical NADH models) shows that for BNAH and AcrH(2), the heterolytic C4-H bond dissociation energies are smaller (by 3.62 kcal mol(-1)) and larger (by 7.4 kcal mol(-1)), respectively, than the corresponding homolytic C4-H bond dissociation energy. However, for HEH, the heterolytic C4-H bond dissociation energy (69.3 kcal mol(-1)) is very close to the corresponding homolytic C4-H bond dissociation energy (69.4 kcal mol(-1)). These results suggests that the hydride is released more easily than the corresponding hydrogen atom from BNAH and vice versa for AcrH(2), and that there are two almost equal possibilities for the hydride and the hydrogen atom transfers from HEH. Examination of the two sets of the (C4-H)(.+) bond dissociation energies shows that the homolytic (C4-H)(.+) bond dissociation energies are much larger than the corresponding heterolytic (C4-H)(.+) bond dissociation energies for the ten NADH models by 23.3-34.4 kcal mol(-1); this suggests that if the hydride transfer from the NADH models is initiated by a one-electron transfer, the proton transfer should be more likely to take place than the corresponding hydrogen atom transfer in the second step. In addition, some elusive structural information about the reaction intermediates of the NADH models was obtained by using Hammett-type linear free-energy analysis.

Heat stress (HS) annually causes huge losses to global dairy industry, including animal performance decrease, metabolic disorder and health problem. So far, physiological mechanisms underlying HS of dairy cows still remain elusive. To our best knowledge, this is the first attempt to elucidate the HS-induced metabolic disorders of dairy cows using integrated (1)H NMR and LC-MS-based metabolic study. The results not only provided potential diagnostic biomarkers for HS lactating dairy cows, but also significantly explored the related physiological mechanisms of metabolic pathway shifts induced by HS environment. This work offers comprehensive insights into the global metabolic alterations of dairy cows exposed to HS and provides a new perspective for further study.

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Heat stress (HS) damages the global dairy industry by reducing milk yields and quality, harming health, and damaging the reproduction of dairy cows, causing huge economic losses each year. However, an understanding of the physiological mechanism of HS lactating dairy cows remains elusive. Here, a metabolomics study using LC-MS and 1H NMR spectroscopy was performed to analyze the metabolomic differences in the milk between HS-free and HS dairy cows, and discover diagnostic biomarkers and changes in the metabolic pathway. A total of 53 discriminating metabolites were significantly up- or down-regulated in the HS group compared with the HS-free group (P < 0.05). These biomarkers were involved in pathways of carbohydrate, amino acid, lipid, and gut microbiome-derived metabolism. Comparing these potential biomarkers with previously identified HS candidate biomarkers in plasma, significant correlations between the levels of lactate, pyruvate, creatine, acetone, β-hydroxybutyrate, trimethylamine, oleic acid, linoleic acid, lysophosphatidylcholine 16:0, and phosphatidylcholine 42:2 in milk and plasma were found, indicating that the blood-milk barrier became leaky and the levels of these 10 biomarkers in milk can reflect HS-induced metabolomic alterations in blood. These novel findings can support more in-depth research to elucidate the milk-based changes in metabolic pathways in HS lactating dairy cows.

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