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…     

ＰＳⅠ颗粒光抑制的可能机理

从菠菜（Spinacia oleracea L.)叶绿体中提取的ＰＳⅠ颗粒中加入不同浓度的组氨酸,利用光谱和ＳＤＳ－ＰＡＧＥ技术研究了强光（２３００μmol.m^-2.s^-1）处理过程中外加组氨酸对色素和多肽光破坏进程的影响,强光处理可以使ＰＳⅠ颗粒的光吸收减小,在照光３０min后外加组氨酸有效地抑制了光吸收减小的趋势。外加组氨酸在照光约１０min后对ＰＳⅠ颗粒ＣＤ信号的下降也起到了明显的抑制作用。外加组氨酸对ＰＳⅠ颗粒中色素保护作用的这种延迟现象表明,在强光照初期和后期ＰＳⅠ颗粒光抑制的机理可能不同。外加组氨酸还可以有效地抑制光照过程中ＰＳⅠ颗粒７７Ｋ荧光产量的下降,ＳＤＳ－ＰＡＧＥ分析结果表明,外加组氨酸在光照过程中不但对ＰＳⅠ颗粒的反应中心蛋白可以起到保护作用,对其他多肽组分同样有显的保护作用。     

田间小麦叶片光合作用的光抑制不伴随D1蛋白的净降解

通过测定田间小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ ）叶片Ｄ１蛋白的含量、光合放氧和叶绿素ａ 荧光,探讨了叶片光合作用的光抑制与Ｄ１蛋白净降解的关系。田间的小麦叶片受到晴天中午光照约３ ｈ 以后,表观光合量子效率（Φ）、光系统Ⅱ的光化学效率（Ｆｖ／Ｆｍ ）和初始荧光（Ｆ０）明显下降;若将叶片转入弱光下,这３个指标可在１ ｈ 内基本恢复;强光照射过程中Ｄ１蛋白的含量没有显著变化;Ｄ１蛋白合成抑制剂ＳＭ 使强光下叶片的慢驰豫的非光化学荧光猝灭（ｑＥ－ｓｌｏｗ ）明显增加;在弱光下恢复时引入链霉素（ＳＭ）不影响叶片光合功能的恢复;用二硫苏糖醇（ＤＴＴ）抑制叶黄素循环使中午强光照射后的叶片中Ｄ１蛋白的含量降低３０％ 左右。这些结果都表明,田间小麦叶片光合作用的光抑制不是由于Ｄ１蛋白的净降解,而是由于非辐射能量耗散的增加引起的。     

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     

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…     

光抑制条件下水稻籼粳亚种及其正反交F_1杂种的PSⅡ光化学效率和CO_2交换特点

测定了水稻（ＯｒｙｚａｓａｔｉｖａＬ．）不同正反交组合的ＰＳⅡ电子传递活性、Ｄ１蛋白量、叶绿素ａ荧光、净光合速率（ＰＮ）、光呼吸速率（ＰＲ）、ＲｕＢＰＣａｓｅ／Ｏａｓｅ活性,并对ＲｕＢＰＣａｓｅ进行了动力学分析。结果表明：光抑制条件下粳（ｊａｐｏｎｉｃａ）亚种中Ｄ１蛋白净降解少,ＰＳⅡ电子传递活性和光化学效率高,表现耐光抑制,而籼（ｉｎｄｉｃａ）亚种则相反,籼、粳正反交Ｆ１的上述指标介于双亲值之间且偏向其母本。进一步观察它们的ＣＯ２交换特点,所有基因型水稻ＰＲ保持稳定、ＰＮ降低,因而ＰＲ／ＰＮ增加。与耐光抑制的粳亚种相比,对光抑制敏感的籼亚种中ＰＮ降低较多、ＰＲ／ＰＮ增加较多。正反交Ｆ１杂种的ＰＲ／ＰＮ介于双亲值之间且偏向其母本。ＣＯ２交换的关键酶ＲｕＢＰＣａｓｅ／Ｏａｓｅ活性和ＲｕＢＰＣａｓｅ动力学参数没有变化且在基因型间无差异。相关分析表明,Ｄ１蛋白量与Ｆｖ／Ｆｍ、ＰＲ／ＰＮ的相关系数分别为０．９５０１和－０．９７６８。看来,质基因编码的Ｄ１蛋白是籼粳杂种稻光抑制特性及其生理遗传的分子基础。     

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。     

PSⅠ颗粒光抑制的可能机理(英文)

从菠菜 (SpinaciaoleraceaL .)叶绿体中提取的PSⅠ颗粒中加入不同浓度的组氨酸 ,利用光谱和SDS_PAGE技术研究了强光 ( 2 30 0 μmol·m-2 ·s-1)处理过程中外加组氨酸对色素和多肽光破坏进程的影响。强光处理可以使PSⅠ颗粒的光吸收减小 ,在照光 30min后外加组氨酸有效地抑制了光吸收减小的趋势。外加组氨酸在照光约 10min后对PSⅠ颗粒CD信号的下降也起到了明显的抑制作用。外加组氨酸对PSⅠ颗粒中色素保护作用的这种延迟现象表明 ,在强光照初期和后期PSⅠ颗粒光抑制的机理可能不同。外加组氨酸还可以有效地抑制光照过程中PSⅠ颗粒 77K荧光产量的下降。SDS_PAGE分析结果发现 ,外加组氨酸在光照过程中不但对PSⅠ颗粒的反应中心蛋白可以起到保护作用 ,对其他多肽组分同样有显著的保护作用     

鲁山冬凌草丁素的结构

从河南省鲁山县产冬凌草叶中分得一个新的对映-贝壳杉烯型二萜化合物,命名为鲁山冬凌草丁素,经光谱和化学方法证明,其结构如(1)式所示。     

我国东喜马拉雅及其邻区牛肝菌目的研究（续）

本属与多种树种有菌根关系：如Pinus,Larix,Abies和Pseudotsuga,但在Larix林下,本菌往往与土壤中的鞣料相聚集,对周围某些植物根系不利。本属现知15种,本区6种。     

THE MODE OF ACTION OF VITAMIN D

1. The purpose of this review article is to re-evaluate and integrate many of the observations related to the physiological effects of vitamin D, using as a working hypothesis the concept that the vitamin may be acting analogously to a steroid hormone in terms of its ability to interact with genetic information and ultimately elicit a physiological response. Prior to this time the problem of the mechanism of action of vitamin D has primarily been approached from the point of view that the vitamin was acting as a cofactor for some specific enzymic reaction. 2. The physiological activities of vitamin D are integrated with those of parathyroid hormone to provide a homeostatic control for the regulation of primarily calcium and secondarily phosphate metabolism. It is proposed that the role of vitamin D in this homeostatic control mechanism is older and more fundamental than that of parathyroid hormone. The interaction of vitamin D on skeletal calcium metabolism may have evolved before the effects of the vitamin on intestinal calcium absorption. 3. There are several physiological defects of calcium metabolism—rickets, osteo-malacia, vitamin D-resistant rickets and idiopathic hypercalcaemia—all of which may be a consequence of an aberration in one or another of the interlocking steps of the vitamin D-dependent and calcium-dependent homeostatic control mechanism. 4. The most thoroughly established action of vitamin D in vivo is to promote or facilitate the intestinal absorption of calcium. Although the exact biochemical details of this process are not available, this may involve vitamin D-mediated synthesis of the appropriate enzyme systems or the alteration of membrane structure necessary for calcium absorption. It is not yet unequivocally established whether calcium absorption is an energy-dependent active transport process or is a passive carrier-mediated or simple diffusion process. 5. The exact action of vitamin D on bone metabolism is not as well established, but the primary effect of the vitamin is likely to mediate bone resorption. The vitamin D-dependent activities of the cell in both the intestine and bone are to absorb calcium and transfer it to the blood. 6. No direct effects of vitamin D on intestinal absorption of phosphate have been found. Furthermore the validity of a vitamin D-mediated renal reabsorption of phosphate is questioned, for the major effects of vitamin D are cation oriented. If the renal effects of vitamin D are true, it is postulated that the mechanism of action of the vitamin here on the anion, phosphate, is fundamentally different from its cation oriented mechanism. 7. There is a lag in the action of vitamin D on the vitamin mediated: (a) transport of calcium both in vivo in rats and chicks, and in vitro with everted intestinal slices; (b) the apparent increased permeability of intestinal mucosa; (c) increased levels of citric acid in serum or bone; (d) the increased incorporation of radioactive inorganic phosphorus into intestinal mucosa phospholipids. As shown by the use of radioactive vitamin D, this lag is not due to a lack of the vitamin in the target organs. 8. Whereas large, unphysiological doses of radioactive vitamin D localize in all tissues and all subcellular fractions, small physiological doses of radioactive vitamin D localize predominantly in the nucleus of the intestinal mucosa. The amount of vitamin D localized in the nucleus would appear to be too low for the vitamin to function as a cofactor, and is more indicative of an interaction on or with deoxy-ribonucleic acid. 9. Actinomycin D, an inhibitor of DNA-directed RNA synthesis, inhibits the action of vitamin D in mediating intestinal calcium absorption and bone resorption. Vitamin D also stimulates messenger-RNA synthesis in intestinal mucosa within 1/2 hr. of vitamin treatment. Vitamin D may play a crucial role, along with parathyroid hormone and calcium, in a DNA, gene-dependent, homeostatic control mechanism for cal, ium metabolism. In this system the vitamin D molecule has certain very specific structural requirements which are probably a reflection of the specificity of its receptor molecule, rather than structural requirements for a cofactor-enzyme relationship.     

大萼香茶菜丁素的化学结构

从大萼香茶菜叶中又分得一个具有细胞毒活性的新的二萜类化合物,命名为大萼香茶菜丁素(macrocalyxin D)。根据光谱和化学数据鉴定其化学结构为[3]。     

大萼变型丁素的化学结构

继大萼变型甲素和乙素之后,从大萼香茶菜变型 Rabdosia macrocalyx(Dunn.)Haraform 干叶的乙醇提取物中又分离出一种新的二萜,命名为大萼变型丁素。初步的药理试验表明其具有明显的细胞毒作用和较强的抑菌作用。根据光谱和化学证据,确定了大萼变型丁素的结构为(Ⅲ)式。     

Nano-viewpoint in Modeling and Investigation of the D/M/D Transparent-Conductive Layer

Plasmonics - A transparent-conductive film (TCF) is widely used in various electro-optical devices. The dielectric/metal/dielectric (D/M/D) as one type of TCF has been highly considered due to more...     

Familial D/E translocation

Summary A familial D/E translocation is described. The proposita, a girl with features of the trisomy-E₁ syndrome, had 47 chromosomes. The extra chromosome was a small acrocentric one. Her mother and little brother had 46 chromosomes, and showed a missing chromosome in the groups D and E, and an extra chromosome in the groups C and G. The former had a subterminal centromere. The latter could not be dinstinguished morphologically from the other small acrocentrics.The morphology and the autoradiographic analysis of the chromosomes concerned in the translocation, indicated that it was a (17q+; 14q-) translocation. It could also be proved that the extra chromosome of the proposita represented mainly a partial trisomy 14. The father and little sister of the patient had a normal karyotype.A comparison of the karyotypes, found in the children of the present family and in cases of D/E-translocation reported in the literature, pointed to a high frequency of non-disjunction in D/E-translocation carriers. As a possible explanation, a convergent orientation of a trivalent at metaphase I of meiosis is proposed.     

Identification of D/D translocations in mentally retarded patients

Summary Routine chromosome analysis of two patients with severe mental retardation revealed two 45,D-,D-,t(DqDq)+karyotypes. With the aid of a Giemsa banding technique the translocation chromosomes were identified as a t(13q14q) and a t(14q15q).

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Zusammenfassung Eine Routine-Chromosomenanalyse von zwei Patienten mit geistiger Retardation zeigte zwei 45,D-,D-,t(DqDq)+-Karyotypen. Mit Hilfe einer Giemsamusterfärbung war es möglich, die respektiven Translokationschromosomen als t(13q14q) und t(14q15q) zu identifizieren.