Thermodynamic analysis and transition state study for pyrolysis of levoglucosan and glyceraldehyde through quantum simulation

In order to better understand the pyrolysis process of cellulose, the decomposition of levoglucosan and glyceraldehyde, which are important intermediate products of cellulose, are simulated by quantum simulation. Thermodynamic analysis of four possible reaction pathways for levoglucosan is conducted by quantum chemistry.The reaction process of glyceraldehyde is checked, and the intermediates and the activation energies of the process are given. The simulation results indicate that the three well-established chemical pathways for levoglucosan in literature can spontaneously occur within the pyrolysis temperature range from 500 to 1 000 K. However, the reaction pathway involving the formation of erythrose cannot be accepted since the free energy ΔG is estimated to be above zero during the pyrolysis process. Through the analysis of glyceraldehyde decomposition by the transition state theory, decarbonylation and dehydration may be the dominant pathways for glyceraldehyde decomposition. The quantum simulation for determining the chemical pathway of glyceraldehyde and levoglucosan can give a conceptual and methodological guide for searching possible chemical pathways of cellulose pyrolysis or other macromolecules in biomass.

LARGE SCALE PURIFICATION OF PHOSPHOGLYCERATE KINASE（PGK） AND GLYCERALDEHYDE 3－PHOSPHATE DEHYDROGENASE（GAPDH） FROMYELLOW PEAS BY PEG／REPPAL PES AQUEOUS TWO PHASE SYSTEM AND ION EXCHANGE CHROMATOGRAPHY

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Sperm glyceraldehyde 3-phosphate dehydrogenase gene expression in asthenozoospermic spermatozoa

It has been suggested that the energy required for sperm motility is produced by oxidative phosphorylation while glycolysis seems to be an important source for ATP transmission along the flagellum. Some studies have investigated the chemical and kinetic properties of the enzyme glyceraldehyde 3-phosphate dehydrogenase to identify any changes in the regulation of glycolysis and sperm motility. In contrast, there are few studies analyzing the genetic basis of hypokinesis. For this reason, we investigated the glyceraldehyde 3-phosphate dehydrogenase gene in human sperm to evaluate whether asthenozoospermia was correlated with any changes in its expression. Semen examination and glyceraldehyde 3-phosphate dehydrogenase gene expression studies were carried out on 116 semen samples divided into two groups - Group A consisted of 58 normokinetic samples and Group B of 58 hypokinetic samples. Total RNA was extracted from spermatozoa, and real-time PCR quantification of mRNA was carried out using specific primers and probes. The expression profiles for the Groups A and B were very similar. The mean delta Ct was as follows - Group A, 5.79 ＋ 1.04; Group B, 5.47 ＋ 1.27. Our study shows that in human sperm, there is no difference in glyceraldehyde 3-phosphate dehydrogenase gene expression between samples with impaired motility and samples with normal kinetics. We believe that this study could help in the understanding of the molecular mechanisms of sperm kinetics, suggesting that hypomotility may be due to a possible posttranscriptional impairment of the control mechanism, such as mRNA splicing, or to posttranslational changes.

Glycer-AGEs-RAGE signaling enhances the angiogenic potential of hepatocellular carcinoma by upregulating VEGF expression

AIM:To investigate the effect of glyceraldehyde-derived advanced glycation end-products(Glycer-AGEs) on hepatocellular carcinoma(HCC)cells.METHODS:Two HCC cell lines(Hep3B and HepG2 cells)and human umbilical vein endothelial cells(HUVEC)were used.Cell viability was determined using the WST-8 assay.Western blotting,enzyme linked immunosorbent assay,and real-time reverse transcriptionpolymerase chain reactions were used to detect protein and mRNA.Angiogenesis was evaluated by assessing the proliferation,migration,and tube formation of HUVEC.RESULTS:The receptor for AGEs(RAGE)protein was detected in Hep3B and HepG2 cells.HepG2 cells werenot affected by the addition of Glycer-AGEs.GlycerAGEs markedly increased vascular endothelial growth factor(VEGF)mRNA and protein expression,which is one of the most potent angiogenic factors.Compared with the control unglycated bovine serum albumin(BSA) treatment,VEGF mRNA expression levels induced by the Glycer-AGEs treatment were 1.00±0.10 vs 1.92 ±0.09(P<0.01).Similarly,protein expression levels induced by the Glycer-AGEs treatment were 1.63±0.04 ng/mL vs 2.28±0.17 ng/mL for the 24 h treatment and 3.36±0.10 ng/mL vs 4.79±0.31 ng/mL for the 48 h treatment,respectively(P<0.01).Furthermore,compared with the effect of the control unglycated BSA-treated conditioned medium,the Glycer-AGEstreated conditioned medium significantly increased the proliferation,migration,and tube formation of HUVEC,with values of 122.4%±9.0%vs 144.5%±11.3%for cell viability,4.29±1.53 vs 6.78±1.84 for migration indices,and 71.0±7.5 vs 112.4±8.0 for the number of branching points,respectively(P<0.01).CONCLUSION:These results suggest that Glycer-AGEs-RAGE signaling enhances the angiogenic potential of HCC cells by upregulating VEGF expression.

Base-free aerobic oxidation of glycerol on TiO_2-supported bimetallic Au–Pt catalysts

The aerobic oxidation of glycerol provides an economically viable route to glyceraldehyde, dihydroxyacetone and glyceric acid with versatile applications, for which monometallic Pt, Au and Pd and bimetallic Au-Pt, Au- Pd and Pt-Pd catalysts on TiO2 were examined under base-free conditions. Pt exhibited a superior activity relative to Pd, and Au-Pd and Pt-Pd while Au was essentially inactive. The presence of Au on the Au-Pt/TiO2 catalysts led to their higher activities （normalized per Pt atom） in a wide range of Au/Pt atomic ratios （i.e. 1/3-7/1 ）, and the one with the Au/Pt ratio of 3/1 exhibited the highest activity. Such promoting effect is ascribed to the increased electron density on Pt via the electron transfer from Au to Pt, as characterized by the temperature-programmed desorption of CO and infra-red spectroscopy for CO adsorption. Meanwhile, the presence of Au on Au-Pt/TiO2, most like due to the observed electron transfer, changed the product selectivity, and facilitated the oxidation of the secondary hydroxyl groups in glycerol, leading to the favorable formation of dihydroxyacetone over glyceraldehyde and glyceric acid that were derived from the oxidation of the primary hydroxyl groups. The synergetic effect between Au and Pt demonstrates the feasibility in the efficient oxidation of glycerol to the targeted products, for example, by rational tuning of the electronic properties of metal catalysts.