Metabolism of 2-chloro-4-methylphenoxyacetate by Alcaligenes eutrophus JMP 134

2-Chloro-4-methylphenoxyacetate is not a growth substrate for Alcaligenes eutrophus JMP 134 and JMP 1341. It is, however, being transformed by enzymes of 2,4-dichlorophenoxyacetic acid metabolism to 2-chloro-4-methyl-cis, cis-muconate, which is converted by enzymatic 1,4-cycloisomerization to 4-carboxymethyl-2-chloro-4-methylmuconolactone as a dead end metabolite. Chemically, only 3,6-cycloisomerization occurs, giving rise to both diastereomers of 4-carboxychloromethyl-3-methylbut-2-en-4-olide. Those lactones harbonring a chlorosubstituent on the 4-carboxymethyl side chain were surprisingly stable under physiological as well as acidic conditions.     

Anaerobic degradation of dimethylsulfoniopropionate to 3-S-methylmercaptopropionate by a marine Desulfobacterium strain

Dimethylsulfoniopropionate, an osmolyte of marine algae, is thought to be the major precursor of dimethyl sulfide, which plays a dominant role in biogenic sulfur emission. The marine sulfate-reducing bacterium Desulfobacterium strain PM4 was found to degrade dimethylsulfoniopropionate to 3-S-methylmercaptopropionate. The oxidation of one of the methyl groups of dimethylsulfoniopropionate was coupled to the reduction of sulfate; this process is similar to the degradation betaine to dimethylglycine which was described earlier for the same strain. Desulfobacterium PM4 is the first example of an anaerobic marine bacterium that is able to demethylate dimethylsulfoniopropionate.Abbreviations DMSP dimethylsulfoniopropionate - DMS dimethyl sulfide - MMPA 3-S-methylmercaptopropionate     

Effect of dissolved inorganic carbon on the expression of carboxysomes,localization of Rubisco and the mode of inorganic carbon transport in cells of the cyanobacterium Synechococcus UTEX 625

In the cyanobacterium Synechococcus UTEX 625, the extent of expression of carboxysomes appeared dependent on the level of inorganic carbon (CO₂+HCO _inf3 ^sup- ) in the growth medium. In cells grown under 5% CO₂ and in those bubbled with air, carboxysomes were present in low numbers (<2 · longitudinal section^-1) and were distributed in an apparently random manner throughout the centroplasm. In contrast, cells grown in standing culture and those bubbled with 30 l CO₂ · 1^-1 possessed many carboxysomes (>8 · longitudinal section^-1). Moreover, carboxysomes in these cells were usually positioned near the cell periphery, aligned along the interface between the centroplasm and the photosynthetic thylakoids. This arrangement of carboxysomes coincided with the full induction of the HCO _inf3 ^sup- transport system that is involved in concentrating inorganic carbon within the cells for subsequent use in photosynthesis. Immunolocalization studies indicate that the Calvin cycle enzyme ribulose bisphosphate carboxylase was predominantly carboxysome-localized, regardless of the inorganic carbon concentration of the growth medium, while phosphoribulokinase was confined to the thylakoid region. It is postulated that the peripheral arrangement of carboxysomes may provide for more efficient photosynthetic utilization of the internal inorganic carbon pool in cells from cultures where carbon resources are limiting.Abbreviations Chl chlorophyll - DIC dissolved inorganic carbon (CO₂+HCO _inf3 ^sup- +CO _inf3 ^sup2- ) - PRK phosphoribulokinase - RuBP ribulose 1,5-bisphosphate - Rubisco LS large subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase     

Gluconeogenesis from pyruvate in the hyperthermophilic archaeon Pyrococcus furiosus: involvement of reactions of the Embden-Meyerhof pathway

The hyperthermophilic archaeon Pyrococcus furiosus was grown on pyruvate as carbon and energy source. The enzymes involved in gluconeogenesis were investigated. The following findings indicate that glucose-6-phosphate formation from pyruvate involves phosphoenolpyruvate synthetase, enzymes of the Embden-Meyerhof pathway and fructose-1,6-bisphosphate phosphatase.Cell extracts of pyruvate-grown P.furiosus contained the following enzyme activities: phosphoenolpyruvate synthetase (0.025 U/mg, 50 °C), enolase (0.9 U/mg, 80 °C), phosphoglycerate mutase (0.13 U/mg, 55 °C), phosphoglycerate kinase (0.01 U/mg, 50 °C), glyceraldehyde-3-phosphate dehydrogenase reducing either NADP⁺ or NAD⁺ (NADP⁺: 0.019 U/mg, NAD⁺: 0.009 U/mg; 50 °C), triosephosphate isomerase (1.4 U/mg, 50 °C), fructose-1,6-bisphosphate aldolase (0.0045 U/mg, 55 °C), fructose-1,6-bisphosphate phosphatase (0.026 U/mg, 75 °C), and glucose-6-phosphate isomerase (0.22 U/mg, 50 °C). Kinetic properties (V _max values and apparent K _m values) of the enzymes indicate that they operate in the direction of sugar synthesis. The specific enzyme activities of phosphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase (NADP⁺-reducing) and fructose-1,6-bisphosphate phosphatase in pyruvate-grown P. furiosus were by a factor of 3, 10 and 4, respectively, higher as compared to maltose-grown cells suggesting that these enzymes are induced under conditions of gluconeogenesis. Furthermore, cell extracts contained ferredoxin: NADP⁺ oxidoreductase (0.023 U/mg, 60 °C); phosphoenolpyruvate carboxylase (0.018 U/mg, 50 °C) acts as an anaplerotic enzyme.Thus, in P. furiosus sugar formation from pyruvate involves reactions of the Embden-Meyerhof pathway, whereas sugar degradation to pyruvate proceeds via a modified non-phosphorylated Entner-Doudoroff pathway.     

白粒济宁3号小麦品种的选育

用快中子照射红粒济宁3号小麦干种子,后代获得白粒植株,经选育而成白粒济宁3号。白粒济宁3号与红粒济宁3号比,除籽粒颜色差别外,籽粒蛋白含量显著高于红粒济宁3号,而落黄性、籽粒饱满度、千粒重、产量均略低于红粒济宁3号,该品种累计种植面积10余万亩。     

10CM短柱快速分离3-MH的实验研究

本研究在改进后短程序基础上,对氨基酸分离柱进行了改进。改进后的分离柱长为10cm。比原来20cm长柱分离3—MH的时间缩短了近1/2。实验所得的(回收率为97.59%,分离度0.89±0.02。变异系数1.17)这些指标较国外用其它方法所得的结果有良好的相关性。多次测定结果说明长柱与短柱比较无明显差异。证明了短柱对3—MH含量无影响。这一改进所建立的方法大大地缩短了样品的分析时间,节约了大量进口试剂,开展这方面的工作将有利益提高严重烧伤、创伤后蛋白质代谢和营养学等方面的研究水平。     

大鼠脑突触质膜糖皮质激素受体的纯化

本文利用抗大鼠肝细胞内糖皮质激素受体的单克隆抗体制备的免疫亲和层析柱,将大鼠脑突触质膜糖皮质激素受体纯化了约1150倍,SDS聚丙烯酰胺簿层梯度凝胶电泳显示,在约67kD处有一较明显的染色条带。     

乙型肝炎病毒表面抗原preS1在大肠杆菌中的表达与鉴定

本文报告利用pWR590质粒为载体,构建了含1ac启动子、β-半乳糖苷酶(1—590)基因、Xa因子的四肽识别位点和HBV preS1、preS2编码序列的表达质粒,并成功地在大肠杆菌中获得稳定表达。融合蛋白经Xa因子消化和高效液相层析,得到了preS1(1—91)纯肽。此肽特异性地与人肝细胞质膜结合,从而为肝细胞上存在preS1受体提供了直接的实验依据,也为分离和鉴定肝细胞上preS1受体打下了良好的基础。     

Changes in ovarian follicles and in vitro sex hormone release in the lizard Podarcis sicula sicula

An in vitro superfusion method was used to test sex hormone release from different kinds of ovarian follicle (growing follicles, postovulatory follicles, and atretic follicles) in the lizard Podarcis sicula sicula. Sex hormone output changes with the stage of follicle evolution and sexual cycle. Previtellogenetic follicles prevail in early-spring quiescent ovaries and secrete mainly progesterone, which is probably utilized at that phase to delay ovarian resumption. In the active ovary, progesterone output from previtellogenetic follicles decreases, whereas vitellogenetic follicles produce a significant amount of 17β-estradiol, which is necessary for sustaining vitellogenin synthesis by the liver and oviduct growth. As follicles become ripe, progesterone production is resumed, and it increases in young postovulatory follicles. This is in line with the functions assigned to the hormone at that phase of the sexual cycle, i.e., the induction of oocyte maturation and the regulation of egg retention in the oviduct. Postovulatory follicles can also synthetize 17β-estradiol. After oviposition, this hormone, which is secreted by the old postovulatory follicles, can reinitiate vitellogenin synthesis, allowing the development of a new oocyte set. Our data confirm that active, although ephemeral, corpora lutea are also formed in oviparous species. A limited contribution to ovarian sex steroid production derives also from atretic follicles, at least at the early stages of the breeding cycle. © 1993 Wiley-Liss, Inc.