Organisms produces reactive oxygen species (ROS) throughout their lives. ROS including superoxide anions, hydroxyl radicals, hydrogen peroxide and singlet oxygen whit known to oxidize biological macromolecules, The accumulation of oxidized, or modified, extra- and intra-cellular proteins in vivo cause age-related diseases such as Parkinson’s disease and cataract. Therefore, it is important to study the damage of proteins by photo-sensitizer. Singlet oxygen is a high reactive oxidant in biology systems, and that proteins are a major target for the damage initiated by this reactive species. Reaction with proteins occurs primarily at Trp, Met, Cys, His, and Tyr side-chains with this resulting in the formation of short-lived endo- or hydroperoxides on Trp, His, and Tyr resi- dues. This paper is a brief introduction about the reactions of singlet oxygen with tyrosine and histidine.
Based on establishing the nanosecond pulse radiolysis system in 1990 and chemical reaction dynamics stud- ies with the system, a picosecond pulse radiolysis system has been proposed and is under installment at Shanghai Institute of Applied Physics. The paper gives a brief introduction to the ps pulse radiolysis system and its applica- tions, especially in antioxidant studies.
Reactive oxygen species (ROS) induce a lot of disease when the balance breaks between ROS and the enzymic and non-znzymic systems in human body to effectively scavenge ROS and prevent them from damaging the body. Proteins, which account for about 20% dry weight of a human cell, may be major target of attacks by ROS. It has been found that hydroxycinnamic acid, flavonoids and some other natural anti-oxidants can scavenge ROS inside body organs and tissues, and repair effectively oxidization damages to proteins. In recent years, stud- ies have been focused on mechanisms of the ROS caused damages to proteins, and on protecting proteins against ROS. In the meantime, explorations have been made on analyzing stable products of proteins involved in oxidation by ROS and on relationships between scavenging effects of natural anti-oxidants and their molecular structures. However, there are problems remaining before us for answers by still more investigations, such as what is the ROS attacking position on a protein macromolecule and how is the molecular modification of the ROS-attacked protein.
The photo-physical and photo-chemical properties of melatonin (ML) werestudied by 266 nm laser flash photolysis (LFP). ML undergoes photo-ionization to produce radicalcation of ML (ML^(·+))and hydrated electrons (e_(aq)^-), while excited triplet state ~3ML~* is alsoformed during photolysis. The oxidation via one electron transfer from ML to SO_4^(·+) and thetriplet state of riboflavin (~3RF~*) has been also investigated and the rate constants for theprocess have been determined to be 8.0x10^9 and 1.4x10^9 L·mol^(-1)·s^(-1) respectively. Theradical cation of 2,2''-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS^(·+)) scavengingcapacities of melatonin and other antioxidants are compared in this paper.
ZHU Hongping1,2, ZHANG Zhaoxia1,2, ZHAO Hongwei1, WANG Wenfeng1 & YAO Side1 1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
利用基于飞秒超快激光的太赫兹时域光谱(terahertz time domain spectroscopy,THz-TDS)对D-木糖、D-核糖、D-阿拉伯糖、D-来苏糖及相关的五元糖进行了研究,得到了它们在0.1～2.0THz波段的THz-TDS吸收谱图.不同糖类化合物的吸收谱表现出明显的特征,表明THz-TDS技术可以分辨化合物结构上的微小差异,可以应用于物质检测与分析.同时还研究比较了不同旋光性五元糖的THz-TDS光谱.
The transient species of gallic acid （GA） have been studied by 266 run nanosecond laser flash photolysis in aqueous solution and acetonitfile. The intermediate with absorption at 320 nm was identified as excited triplet state （^3GA＊）, the decay rates of which were obtained in aqueous solution and acetonitrile respectively. Energy transfer from ^3GA＊ to β-carotene was observed and the energy transfer rate constant kent was determined to be 2.2×10^9 mol^-1·L·s^-1. GA underwent photoionization during photolysis and the quantum yield of photoionization was determined to be 0.12 at room temperature with KI as a reference.
