光破坏的光系统Ⅱ反应中心D1／D2／Cytb559复合物的CD光谱

ＰＳⅡ反应中心Ｄ１／Ｄ２／Ｃｙｔｂ５５９ 复合物的圆二色（ＣＤ）光谱在红区有一个反向带，其正峰在６８０ ｎｍ ，负峰在６６０ ｎｍ 处。光破坏后，该反应中心复合物的ＣＤ信号明显下降，而且当正峰完全消失后，负峰仍然存在，说明该反应中心的ＣＤ信号不仅来源于原初电子供体Ｐ６８０，而且可能来源于其它色素分子     

光系统Ⅱ反应中心D1/D2/Cytb559复合物中去镁叶绿素a的光照破坏

高等植物在强光照射下,光合作用受到抑制。光抑制的分子机理已成为目前光合作用研究中最活跃的研究领域之一［１］。由于叶绿体内色素和蛋白分子很多,其中包含有许多与光破坏不直接相关的组分,因此很难确定具体哪个分子受到破坏。用只含少数色素和多肽分子的光系统Ⅱ（ＰＳⅡ）反应中心Ｄ１／Ｄ２／Ｃｙｔｂ５５９复合物［２］可以解决这个问题,现已证明用光照射该复合物能引起原初电子供体Ｐ６８０的破坏［３,４］,并且是一个多步反应［５］,同时还发现有组氨酸残基的光照破坏［６,７］,当存在电子受体的情况下反应中心内部β－ｃ…     

光系统Ⅱ反应中心D1／D2／cyt b559复合物的组氨酸残基的光照破坏

高等植物在强光照射下光合作用受到抑制。现已普遍认为,光抑制的原初部位是光系统Ⅱ(PS Ⅱ)的反应中心。无论在整个叶片,还是在类囊体膜以及 PS Ⅱ颗粒、放氧颗粒中均能发现光破坏现象。但是,由于在这些颗粒中有许多与光破坏不直接相关的色素和蛋白分子,因此很难确定具体哪个分子受到破坏。而以只含有少数色素和多肽分子的 PSⅡ反应中心 D_1/D_2/cyt b599复合物为材料可以克服这个困难。该反应中心复合物的获得大大推动了光破坏机理的研究。现已证明,D_1/D_2/cyt b559复合物对光照十分敏感,光照可引起原初电子供体 P680的破坏。我们发现该反应中心的破坏是多步     

光系统Ⅱ反应中心复合物中Cytb559的光还原

以分离纯化的光系统Ⅱ反应中心D1/D2/Cyt b559复合物为实验体系,在厌氧条件下,观察到Cytb559的光还原,表明Cyt b559能直接从Pheo~-接受电子,而且Cyt b559的光还原是不可逆的。当外加次级电子受体2,6-二甲基苯醌(DMBQ)与D1/D2/Cyt b559复合物重组之后,Cyt b559的光还原被延迟了,此时电子主要通过DMBQ传递,而且还原的Cyt b559在光照后的暗放置中有部分氧化。作者认为不依赖于醌受体的由Pheo~-到Cyt b559的电子传递是一条新的、次要的电子传递路线,它对光系统Ⅱ反应中心起保护作用。     

质体醌重组的D1／D2／Cytb559复合物的荧光衰减动力学和光破坏作用

光系统Ⅱ反应中心Ｄ１／Ｄ２／Ｃｙｔｂ５５９ 在分离纯化过程中失去了电子受体ＱＡ 和ＱＢ,人工合成的质体醌可以与Ｄ１／Ｄ２／Ｃｙｔｂ５５９ 复合物发生重组。癸基质体醌（ＤＰＱ）与Ｄ１／Ｄ２／Ｃｙｔｂ５９９ 复合物的重组导致该复合物的荧光强度下降及发射光谱蓝移,同时两个与光化学活性相关的长寿命（２４ ｎｓ和７３ ｎｓ）荧光衰减组分占整个荧光的百分数下降,这些结果表明ＤＰＱ作为Ｐｈｅｏ－ 的电子受体,限制了Ｐ６８０＋ ·Ｐｈｅｏ－ 的电荷重组。ＤＰＱ 的加入对Ｄ１／Ｄ２／Ｃｙｔｂ５５９复合物中Ｃｈｌａ 分子的光破坏敏感性影响不大,但β－胡萝卜素在加入ＤＰＱ 之后可以被光照破坏,这个过程可能与β－胡萝卜素的生理功能相关。     

光系统Ⅱ反应中心D1/D2/Cytb559复合物中存在一个与光化学活性无关的去镁叶绿素a

紫色光合细菌反应中心的三维空间结构的解析，极大地推动了光合作用电子传递机理的研究。现已清楚光合细菌反应中心内部存在着两条电子传递支路［１—２］，由于高等植物光系统Ⅱ（ＰＳⅡ）反应中心Ｄ１蛋白和Ｄ２蛋白与光合细菌反应中心Ｌ亚基和Ｍ亚基的一级结构具有很大的相似性，推测ＰＳⅡ反应中心内部也可能存在类似的结构。从高等植物叶绿体中分离纯化的ＰＳⅡ反应中心Ｄ１／Ｄ２／Ｃｙｔｂ５５９复合物具有原初电荷分离活性［３］，其中含有４—６个Ｃｈｌａ分子，２个Ｐｈｅｏａ分子，１—２个β－胡萝卜素分子，它们是否像光合细菌…     

D1／D2／Cyt—559复合物的共振拉曼光谱

光系统Ⅱ（ＰＳⅡ）反应中心Ｄ１／Ｄ２／Ｃｙｔｂ－５５９复合物在４８８ｎｍ处激发的共振拉曼谱显示４个主要谱带,其峰位分别在１５３２（ｖｌ）１１６５（ｖ２）１０１０（ｖ３）和９７０（ｖ４）ｃｍ＾－１处,表明ＰＳⅡ反应中心结合的β－胡萝卜素分子是全反式构型。Ｄ１／Ｄ２／Ｃｙｔｂ－５５９复合物在色素抽提液的拉曼光谱也显示４个主要的拉曼峰,其中ｖ４谱带的强度急剧下降,说明ＰＳⅡ反应中心内部结合的β－胡萝卜素     

菠菜叶绿体光系统Ⅱ反应中心D1／D2／cyt b559长寿命荧光组分的来源

通过多频相位调制法测得菠菜叶绿体光系统Ⅱ（ＰＳⅡ）反应中心Ｄ１／Ｄ２／ｃｙｔｂ５５９复合物的荧光衰减包括４个组分,其寿命分别大约为１、６、２４和７３ｎｓ,所占整个荧光的比例依次为５％、３４％、３５％和２６％。而寿命为６ｎｓ的组分来源于与电荷分离不相关的ｃｈｌａ分子,寿命为１ｎｓ的组分所占的比例很小,其来源不清楚。其中两个长寿命组分都与样品的光化学活性相关,但彼此又是不相关的,很可能来源于电荷分离后的两个不同的重组过程。     

METHYLATED AMINO ACID RESIDUES OF PROTEINS OF BRAIN AND OTHER ORGANS

—Methods for the determination of methyl-lysine, methyllarginine and methylhistidine residues of tissue proteins are described. They consist of preliminary purification of basic amino acids, enzymic removal of lysine, arginine and histidine followed by amino acid analysis. Recovery rates and specificities of the method were satisfactory. The contents of methylamino acids in proteins of mammalian organs were determined. The distribution of proteins containing the methylamino acids in human brain showed that the concentrations of methyl-lysine and N^G,N′^G-dimethylarginine were highest in the gray matter of the cerebellar cortex and relatively high in regions rich in gray matter, while those of N^G-mono- and N^G,N′^G-dimethylarginine were highest in the white matter. The following findings suggest that most of the N^G-mono- and N^G,N′^G-dimethylarginine was associated with the myelin basic protein. The distribution of the methylarginine residues of acid-soluble proteins in bovine brains coincided with the cerebroside pattern. The concentrations of the amino acids in acid-soluble proteins of rat brain increased concomitantly with the increase of cerebroside. The methylamino acid content in proteins increased during the purification of the myelin basic protein from the white matter of human and bovine brains. Proteins containing N^G,N^G-dimethyiarginine and di- and trimethyl-lysine are concentrated in cell nuclei. The first amino acid was found mainly in nucleoplasmic proteins and the other two were found in histones. The concentration of 3-methylhistidine residue, highest in muscular proteins, is low in cerebral proteins and is probably derived from proteins of walls of blood vessels in the brain.     

AMINO ACID AND UREA UPTAKE IN TEN SPECIES OF CHLOROPHYTA1

The Uptake of radioartively-labelled mixed amino acids, arginine, lysine, leucine, glutamic acid and urea was examined in six species of Volvocales and four species of Chlarococcales grown in nitrate-containing medium. Nonradioactive amino acids in excess were used to estimate specificity of amino and carriers in selected cases. All ten species possess salurable (hence, carrier-mediated) systems for uptake of both arginine and urea. In all Volvacales and one Chlorococcales, the arginine-speciftc carrier (which also transported lysine with lower efficiency) was the only amino acid carrier detected. Three species of Chlororoccales appear to possess a separate carrier for lysine and two of these appear to possess at least one additional carrier that is involved in uptake of non-basic amino acids.     

鲤、鲫肌肉水解氨基酸和游离氨基酸的初步研究

本文是对天津地区的两种重要的经济淡水鱼鲤、鲫肌肉水解氨基酸和游离氨基测定,并初步分析比较的结果。       

用猪血制备复合氨基酸及其应用的研究

<正> 我国猪血资源非常丰富,据统计,江苏省各肉联厂的猪血全部收集起来,每年可制成血粉约8000吨,全国大约是这个数字的10倍。但是这些猪血的大部分没有利用,既浪费了资源又污染了环境。猪血中含有大量的蛋白质,如何充分而合理地利用猪血中的蛋     

猪血粉制备复合氨基酸工艺研究

本文采用正交试验法优选硫酸水解猪血粉制备复合氨基酸的最佳条件,经中试及工业规模生产证明:复合氨基酸收率平均为53.3％,氨基酸含量为72.7％。     

氨基酸残基无序排列对蛋白质分子电子能谱的影响

我们用Dean负因子计数方法计算了氨基酸残基无序排列的蛋白质分子的电子能谱。结果表明当含有较多种氨基酸时,无序蛋白质分子的价带很宽,这样价带中的空穴就有很大的迁移率。     

NEUROTOXICITY OF A NON-METABOLIZABLE AMINO ACID, 1-AMINOCYCLOPENTANE-1-CARBOXYLIC ACID: ANTAGONISM BY AMINO ACIDS IN CULTURES OF CEREBELLUM

Abstract— The non-metabolizable amino acid 1-aminocyclopentane-1-carboxylic acid (ACPC) induced degeneration of myelinated axons but spared nerve cell bodies in well myelinated organotypic cultures of cerebellum. The ACPC concentrations used were comparable to those which induce axonal degeneration in vivo. Developing unmyelinated cultures were more sensitive to ACPC than mature cultures and newly myelinating axons appeared to be particularly affected. Supplementing the medium with amino acids, but not with vitamins, prevented toxicity at the lower concentrations of ACPC and afforded considerable protection against the highest concentrations. The protective effect of amino acids could not be accounted for by inhibition of intracellular ACPC transport. These results are considered in terms of other evidence indicating defective protein metabolism in ACPC-treated mice.