大豆叶片RuBP含量测定及其应用

RuBP(1,5-二磷酸核酮糖)是植物光合碳代谢的重要中间产物。经RuBPCase/Oase的催化,RuBP可与CO_2羧化,行光合碳还原途径(C_3环);也可与O_2作用,行光合碳氧化循环(C_2环)。植物光合器官中RuBP含量可调节和影响光合,光呼吸的强弱,改变Calvin循环的运转状况。因此,测定植物光合器官中的RuBP含量在光合与光呼吸研究中具有重要意义。     

热带作物木瓜C~3/C_4属性的鉴别

林植芳等(1982)从光、CO_2等环境因素对木瓜光合作用的影响进行了研究,并认为某些性状近似于C_3植物,但迄今尚没有人从叶解剖结构、RuBP羧化酶分布角度进行研究来确定木瓜的C_3/C_4属性。我们用免疫荧光直接法研究木瓜叶片内RuBP羧化酶的分布,并用气体交换法测定CO_2补偿点,以鉴别它的C_3/C_4属性。     

苜蓿二磷酸核酮糖(RuBP)羧化酶体内活化作用的调节

苜蓿RuBP羧化酶的初活性和活化作用在不饱和光强下与光合速率一样随光强增加而增加。缺硫培养苜蓿叶片的光合速率和RuBP羧化酶的含量、初活性及总活性均比对照有不同程度的降低,其中酶的初活性与光合速率两者减少的趋势比较接近,说明RuBP羧化酶的初活性可能在光合CO_2固定作用中具有决定作用。然而,缺硫植株中酶的活化作用比对照明显增高。酶的活化作用与叶片中的叶绿素,6-PG,NADPH及ATP相对酶含量的比值成正比,与体内的酶量成反比。     

低浓度NaHSO3促进田间水稻的光合磷酸化和光合作用

用1～2 mmol/L NaHSO3喷施于水稻(Oryza sativa L.)叶面可以提高叶片的光合速率,并能持续3 d以上.在此条件下,光下叶片中的ATP含量明显增高,叶片的叶绿素毫秒延迟荧光加强,反映与光合磷酸化活力有关的跨类囊体膜质子梯度增加.乳熟期喷施2次1 mmol/L NaHSO3后,水稻产量提高约10%.研究表明NaHSO3的主要作用和PMS(phenazine methosulfate)促进光合速率的原因可能类似,都是增加了ATP的供应.与此同时,观察到低浓度NaHSO3可促进水稻中反映循环电子传递的叶绿素荧光在作用光关闭后的短时上升.以上现象表明低浓度NaHSO3的促进作用很可能是通过促进围绕PSⅠ的循环电子传递及其耦联的光合磷酸化而促进水稻光合作用的.     

用未标记免疫酶技术在甘蔗大豆叶片内定位RUBP羧化酶

RuBP羧化酶是绿色植物同化CO_2的关键酶。研究RuBP羧化酶在C_4植物叶片内的分布,有助于阐明C_4植物的光合作用结构和功能的特点,以及RuBP羧化酶对光合作用的调控功能。这种工作具有明显的理论意义和实用价值。     

腺苷三磷酸对RuBP羧化酶的稳定效应及其对酶催化部位的作用

ATP显著提高RuBP羧化酶在低温下贮存的稳定性,并抑制RuBP羧化酶在贮存期间巯基数的减少及高分子聚合体的出现。ATP对RuBP羧化酶的活化作用影响不大,但对催化反应有明显的抑制作用,它是一种相对底物RuBP的竞争性抑制剂。凝胶过滤法显示同位素标记的ATP与酶分子相结合。结果说明:ATP与底物RuBP在酶的催化部位上有共同的结合位置。ATP对RuBP羧化酶的稳定效应以及对酶分子构象变化的影响是通过与RuBP催化部位的结合而起作用的。     

细胞色素C_3在Rhodopseudomonas caosulata载色体光合磷酸化中的作用

细胞色素C_3不仅能增进除去铁氧还蛋白载色体的循环光合磷酸化活性的恢复,而且也增进以DCPIPH_2为电子供体,维生素K_3、反丁烯二酸分别为电子受体构成的非循环光合磷酸化活性的恢复。 氩气相下,细胞色素C_3促进正常载色体光合磷酸化活性的最适浓度是1.8 μmol,当PMS存在时,这一促进作用随C_3浓度的增加而直线上升,然后呈稳态。 Antimycin A(10~(-7)mol/L)能充分抑制C_3参与的光合磷酸化活性,这一抑制现象在PMS存在时消失。 o~-phenanthroline(1×10~(-5)mol/L.)对C_3参与的光合磷酸化活性亦具抑制作用,并被PMS的添加而消失,当浓度提高时(10~(-3)mol/L),抑制现象不因PMS的存在而消失。 氢气相下的载色体光合磷酸化活性比氩气相下的低,并且随着载色体贮存(-20℃)时间的增长而急剧下降,24h贮存,丧失活性达60％。C_3对氢气相下的光合磷酸化活性具明显的促进作用,而铁氧还蛋白则不能,但两者同时存在时,其磷酸化活性显著提高。     

兰属植物光合途径的研究

本文对兰属（Cymbidium）植物的七个种中的10个栽培种的光合途径进行了生理生化研究。结果表明,这些兰属植物叶片的磷酸烯醇式丙酮酸羧化酶（PEPCase）和丙酮酸磷酸双激酶（PPDK）的活性很低,乙醇酸氧化酶的活性较高。在光下用α-羟基吡啶甲烷磺酸（α－HPMS）处理叶片后,乙醇酸积累量明显高于对照。叶绿素a／b比值在1．24—2．69之间。光合速率最低为0.96—3.33μmlCO2m-2S-1。这些结果表明所研究的几种兰属植物均为C3植物。     

谷子生长过程中光合特性的变化

谷子是C_4植物,但叶片中核酮糖1,5-二磷酸羧化酶(RuBPCase,E.C.4.1.1.39)和磷酸烯醇式丙酮酸羧化酶(PEP Case,E.C.4.1.1.31)的活性变化,CO_2补偿点的变化与叶位和叶龄有关。其初生叶和衰老叶并不表现典型的C_4特征,与成熟叶比较,RuBP Case活性和CO_2补偿点都相对较高,而且,也存在着结构上的差别。本实验结果表明所测植物在生长过程中存在着光合特性的变化。     

葡萄糖对鹅原代肝细胞脂质沉积相关基因及酶活性的影响

通过用葡萄糖培养天府肉鹅(Anser cygnoides)原代肝细胞的试验,探讨葡萄糖对肝细胞脂质合成能力的影响.研究发现:0²5 mmol/L葡萄糖对肝细胞上清液中谷草转氨酶(aspartate transaminase,AST)、谷丙转氨酶(alanine amiotransferase,ALT)浓度没有显著影响,35 mmol/L葡萄糖影响显著,但AST、ALT浓度均在正常范围内,表明肝细胞功能正常;油红氧染色实验结果表明:葡萄糖处理后显著增加细胞内脂滴集聚和脂质沉积;25、35 mmol/L葡萄糖能显著增加乙酰辅酶A羧化酶α(acetyl-CoA carboxylaseα,ACCα)、脂肪酸合成酶(fatty acid synthetase,FAS)酶活性;5、25、35 mmol/L葡萄糖都能显著增加ACCα、FAS基因mRNA表达量.因此,葡萄糖能通过上调ACCα、FAS基因mRNA表达量及酶活性诱导肝细胞内脂质沉积.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细