Role of catechin on collagen type I stability upon oxidation: a NMR approach

Abstract

The study focuses on the understanding, at molecular level, the mechanism of interaction between protein and flavonoids. Collagen and catechin interactions were investigated by NMR in solution and solid state. The effect of catechin on the stability of collagen to oxidation was also explored. Collagen was treated with two concentrations of catechin solutions. Oxidation was carried out by incubation of collagen solution with three oxidation systems: Fe(II)/H₂O₂, Cu(II)/H₂O₂, and NaOCl/H₂O₂. The effects of oxidation systems were evaluated by high resolution 1?D and 2?D proton spectroscopy and solid state NMR (¹³C CP MAS) experiments. Interactions between collagen and catechin preferentially occur between catechin B ring and the amino acids Pro and Hyp of collagen. Results showed that both iron and copper oxidation systems were able to interact with collagen by site specific attack. Moreover, catechin protects collagen proline from oxidation by metal/H₂O₂ systems, preventing copper and iron approach to collagene molecule;this behaviour was more evident for the copper/H₂O₂ system.     

Catalytic Oxidation of Dimethyl Ether to Dimethoxymethane over Cs Modified HaPW12O40/SiO2 Catalysts

The attractive utilization route for one-step catalytic oxidation of dimethyl ether to dimethoxymethane was successfully carried out over the H3PW12O40（40%）/SiO2 catalyst, modified by Cs, K, Ni, and V. The Cs modification of H3PW12O40（40%）/SiO2 gave the most promising result of 20% dimethyl ether conversion and 34.8% dimethoxymethane selectivity. Dimethoxymethane could be synthe- sized via methoxy groups decomposed from dimethyl ether through the synergistic effect between the acid sites and the redox sites of Cs modified H3PW12O40（40%）/SiO2.     

常压气相氧化羰基化合成碳酸二乙酯

碳酸二乙酯是一种重要的有机化工原料,可广泛用于合成农药如脱叶灵,医药如喹啉酮衍生物,中间体3-氧硫代羧酸酯,还可用于电子管阴极的镀层[1-3]。生产碳酸二乙酯的传统方法为:无水乙醇与光气反应生成氯甲酸乙酯,氯甲酸乙酯继续与乙醇反应生成碳酸二乙酯后经水洗蒸馏制成。使用光气为原料对设备的要求较高。我们在常压下气相羰基化合成碳酸二乙酯[4]:2ＮＯ+Ｃ2Ｈ5ＯＨ+0.5Ｏ2→2Ｃ2Ｈ5ＯＮＯ+Ｈ2Ｏ(1)ＣＯ+2Ｃ2Ｈ5ＯＮＯ→(Ｃ2Ｈ5Ｏ)2ＣＯ+2ＮＯ(2)产生的一氧化氮可与氧气和乙醇进行反应再生为亚硝酸乙酯,符合原子经济反应且几乎不放出对…     

Degradative analysis of aquatic fulvic acid: CuO oxidation versus pyrolysis after tetramethylammonium hydroxide treatments in air and helium atmospheres

The structural composition of Nordic aquatic reference fulvic acid was investigated using chemical and thermal degradation methods: alkaline CuO oxidation and analytical pyrolysis after tetramethylammonium hydroxide (TMAH) pretreatment. Off-line procedures of the TMAH treatments were carried out under both air and helium atmospheres, with the aim of clarifying the effect of oxygen. Irrespective of the fact that the chemical and thermal degradation methods gave qualitatively quite similar basic products (mainly phenols and phenolic acids together with aromatic and aliphatic carboxylic acids), they also revealed their unique selectivity and efficiency for releasing different kinds of structural constituents. The results verify the formation of additional carboxyl functionality in the CuO oxidation. However, some similar oxidative reactions also appeared to take place during the pretreatment procedures of strongly basic TMAH, especially under an air atmosphere. The use of inert and protective atmosphere during the TMAH pretreatment is therefore recommended for producing more relevant structural information about the complex composition of humic substances.     

铬酸氢根季铵树脂的制备及其对糠醇的氧化

制备了负载铬酸氢根的季铵树脂，研究了以该树脂为氧化剂将糠醇氧化为糠醛的反应，考察了温度，时间、溶剂，树脂与醇的摩尔比对该氧化反应的影响。在优化反应条件下，即以苯为溶剂，n(树脂）：n(醇）＝3．5：1，反应回流10h，糠醛产率达75％，实验中铬酸氢根季铵树脂选择性地将糠醇氧化为糠醛，表明它是一种有效的、可套用的氧化剂。     

Selective Oxidation of Betulin by Cr(VI) Reagents

Oxidation of betulin by pyridinium dichromate, pyridinium chlorochromate, and K₂Cr₂O₇ -H₂SO₄ in the presence of tetrabutylammonium bromide was studied. Products of regioselective C-3, C-28-, and exhaustive oxidation, 28-hydroxylup-20(29)-3-one, 3-hydroxy- and 3-oxolup-20(29)-en-28-al were obtained.     

A novel synthetic method for 2-arylmethyl substituted imidazolines and imidazoles from 2-aryl-1,1-dibromoethenes

Various 2-arylmethylimidazolines were prepared by treating readily available 2-aryl-1,1-dibromoethenes with ethylenediamine under mild conditions and further converted into the corresponding imidazoles smoothly with Swern oxidation.     

Diastereoselective synthesis of the 19-epi-C18-C25 segment of (−)-lasonolide A and an unusual inversion at C19

Diastereoselective construction of the 19-epi-C₁₈-C₂₅ segment of (−)-lasonolide A was achieved using a 5-exo-trigonal mode of radical cyclization for the creation of the contiguous quaternary and tertiary stereogenic centers at C₂₂ and C₂₃ as the key reaction step. During the dehydration stage, it was found that an unusual inversion of configuration took place.     

铁催化剂在碳—氧反应中的热重研究

采用动态TG－DTG，研究了铁催化剂的制备方法、前驱化合物的 种类及 热处理对其在碳－氧反应中催化活性的影响。观察到在干混法制备催化剂时，所用铁盐分解温度越低活性越高。此外还发现，热处理可明显提高由分解温度高的含氧铁盐制备的 催化剂的活性，但对于不含氧铁盐和分解温度低的含氧铁盐无影响。     

金属四苯基卟啉-次氯酸钠模拟体系中芳醛氧化反应的研究

研究了以次氯酸钠为氧化剂在两相条件下芳香醛氧化反应中锰(III)-卟啉的催化性质, 在TPPMn(III)醋酸盐, TPPFe(III)氯化物, TPPCo(II)和TPPNi(II)催化剂中(四苯基卟啉, TPP), 前二个化合物呈现催化活性, 研究表明, OXO-金属卟啉的形成是反应的关键步骤。