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31.
Pea (Pisum sativum L.) chloroplastic phosphoriboisomerase (EC 5.3.1.6) can be purified to apparent homogeneity in less than 2 days time with a 53% yield. Important steps in the purification include heat treatment and pseudoaffinity chromatography on Red H-3BN Sepharose. The purified isomerase has a subunit molecular mass of 26.4 kD. The N-terminal sequence has been determined through 34 residues. pH optima are 7.8 (ribose-5-phosphate) and 7.7 (ribulose-5-phosphate); Km values are 0.9 millimolar (ribose-5-phosphate) and 0.6 millimolar (ribulose-5-phosphate). The enzyme is inhibited by erythrose-4-phosphate, sedoheptulosebisphosphate, glyceraldehyde-3-phosphate, and 3-phosphoglycerate at concentrations close to those found in photosynthesizing chloroplasts. Countercurrent phase partitioning experiments indicate that the pea chloroplastic phosphoriboisomerase interacts physically with phosphoribulokinase. 相似文献
32.
Brefeldin A's effects on endosomes, lysosomes, and the TGN suggest a general mechanism for regulating organelle structure and membrane traffic. 总被引:81,自引:0,他引:81
Addition of brefeldin A (BFA) to most cells results in both the formation of extensive, uncoated membrane tubules through which Golgi components redistribute into the ER and the failure to transport molecules out of this mixed ER/Golgi system. In this study we provide evidence that suggests BFA's effects are not limited to the Golgi apparatus but are reiterated throughout the central vacuolar system. Addition of BFA to cells resulted in the tubulation of the endosomal system, the trans-Golgi network (TGN), and lysosomes. Tubule formation of these organelles was specific to BFA, shared near identical pharmacologic characteristics as Golgi tubules and resulted in targeted membrane fusion. Analogous to the mixing of the Golgi with the ER during BFA treatment, the TGN mixed with the recycling endosomal system. This mixed system remained functional with normal cycling between plasma membrane and endosomes, but traffic between endosomes and lysosomes was impaired. 相似文献
33.
高原鼢鼠挖掘取食活动的能量代价及其最佳挖掘取食行为 总被引:3,自引:1,他引:2
高原鼢鼠(Myospalax baileyi)是青藏高原典型的地下鼠,它主要挖掘取食杂类草之地下根茎,在挖掘过程中形成取食洞道。本文根据此特点,建立了挖掘取食过程中能量代价(E_(?))与取食道结构参数(土丘间距S、侧道长L、取食道半径b及洞道深度D)之间以及取食获能E_(fg)与S和b之间的两个函数关系。分别以挖掘效率极大和取食效率极大为优化目标,导出同样的结果,即相同的最佳土丘间距S_(opt)。通过实验观测,计算出在矮嵩草(Kobresiahumilis)草甸生境条件下,最佳土丘间距S_(opt)=127.4厘米,与野外实测土丘间距(126.30±47.85厘米)无显著差异(t=0.312,P>0.50),表明高原鼢鼠的挖掘及取食行为符合最佳化原则。 相似文献
34.
王国亮;南蓬;龚复俊;朱信强;袁晓;袁萍 《武汉植物学研究》1992,10(4):355-358
利用2DNMR结合其他波谱方法从苦皮藤种子油中鉴定了2个新倍半萜多元酯,它们分别是1α-苯甲酰氧-8β-烟酰氧-9α、11β-2乙酰氧-β-二氢沉香呋喃,1β-苯甲酰氧-2α、8β、9α、11β-4乙酰氧-β-二氢沉香呋喃,命名为苦皮藤酯2和3。 相似文献
35.
袁晓;卢大炎;王国亮;叶婉成 《武汉植物学研究》1992,10(4):359-362
从卫矛科南蛇藤属植物毛枝南蛇藤(Celastrus hookeri Prain)根皮中首次分离出一个红色立方体形结晶,经紫外、红外、高分辨质谱和~(13)C核磁共振谱分析,并与有关文献数据对照,确认是南蛇藤素。作者用薄层扫描和高效液相两种方法初步测定了毛枝南蛇藤根皮和根的木栓化表皮的南蛇藤素含量,结果表明南蛇藤素主要集中在根的木栓化表皮,含量在12%以上,而在整个根皮中的含量大约为1%。 相似文献
36.
活性氧对巨噬细胞呼吸爆发影响及云芝多糖的保护作用 总被引:2,自引:0,他引:2
用化学发光法观察到叔丁基氢过氧化物对培养的小鼠腹腔巨噬细胞呼吸爆发有强烈的抑制作用。云芝多糖经腹腔注射后,能增强巨噬细胞呼吸爆发功能对叔丁基氢过氧化物损伤的抵抗力。云芝多糖处理的巨噬细胞谷胱甘肽过氧化物酶基础活力显著提高,在叔丁基氢过氧化物作用下,云芝多糖处理的巨噬细胞仍有较高的谷胱甘肽过氧化物酶活力。说明巨噬细胞的免疫功能与谷胱甘肽过氧化物酶活力有关,非特异性免疫多糖可提高细胞抗氧化能力,减轻活性氧损伤作用。 相似文献
37.
38.
乙型肝炎病毒(HBV)的核心抗原基因(C基因)编码185个氨基酸残基,在原核细胞或痘苗病毒系统中能表达并装配成27nm大小的核心抗原(HBcAg)多聚体颗粒。已证实HBV C基因3′端编码近40个氨基酸的碱基序列,不是表达形成HBcAg颗粒所必需的。用外源基因替换这部分序列,已表达出表面带有外源基因产物的杂合颗粒,它具有很好的免疫原性,成为新型的基因工程多决定簇颗粒载体疫苗。但我们的实验中发现,用另外的外源基因替换3′端序列能显著影响HBV C基因在大肠杆菌中的表达,不同组成的外源基因其影响程度有所不同。 相似文献
39.
The effect of fluorosis on lactation, lactotroph function and ultrastructure were studied in lactating rats. The results were as follows: 1) Inhibition of lactation in lactating rats with chronic fluorosis was assessed by stunting growth of pups and decrease in the amount of milk suckled by pups in 30 min. Metoclopramide, a blocker of dopamine receptor, could improve lactation in these rats. 2) During chronic fluorosis serum PRL level was decreased, however, PRL content in pituitary was increased. Electronmicroscopic examination showed accumulation of large mature secretory granules and appearance of extremely large abnormal secretory granules in lactotroph cytoplasma. These findings indicate that hormone release of pituitary lactotrophs is obstructed in lactating rats with fluorosis, and the toxic effect of fluoride is mediated by an enhanced function of dopaminergic system in hypothalamus. 相似文献
40.
Following application of stoichiometric amounts of Ca2+ or specific partner peptides to spinach calmodulin, dynamic changes in the nanosecond range could be monitored at a strategically anchored fluorescence or spin probe. For these studies the single cysteinyl residue 26 of spinach calmodulin was labelled with a thiol-specific proxyl (i.e. 2,2,5,5-tetramethyl-1-pyrrolidinyl-oxyl) spin probe or with a bimane fluorescence probe. With Ca2+ and a specific ligand (mastoparan) present, fluorescence studies (anisotropy, lifetime) indicated that the rotational motion of the protein complex becomes slower relative to the motion of calmodulin in the absence of the specific ligand. The probe's attachment site 26 appears to reside in a fairly polar microenvironment as reported by a series of proxyl spin probes varying in label length. The rotational correlation time of the shortest spin probe markedly changed upon binding of a specific peptide to a calmodulin region distant from that of the monitoring spin probe. We interpret these observations as indicating that ligand-triggered conformational perturbations are eliciting specific responses at the cysteinyl residue 26 of spinach calmodulin. 相似文献