Assay of L-3-hydroxyacyl-coenzyme A dehydrogenase with substrates of different chain lengths

A method for assaying L-3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35) which permits rate measurements with L-3-hydroxyacyl-CoA substrates of various chain lengths at physiological pH is described. The method is based on a coupled assay system in which 3-ketoacyl-CoA compounds formed by the dehydrogenase are cleaved by 3-ketoacyl-CoA thiolase (EC 2.3.1.16) in the presence of CoASH. The advantages of this assay method are its irreversibility and elimination of product inhibition. The assay procedure was used to determine the kinetic parameters (Km, Vmax) of pig heart L-3-hydroxyacyl-CoA dehydrogenase with several substrates of various chain lengths. The data obtained show the enzyme to be most active with medium-chain substrates whereas Km values for medium-chain and long-chain substrates are almost equal but much lower than those previously reported.     

Effects of acetylene on hydrogenases from the sulfate reducing and methanogenic bacteria

The effect of acetylene on the activity of the three types of hydrogenase from the anaerobic sulfate reducing bacteria has been investigated. The (Fe) hydrogenase is resistant to inhibition by acetylene while the nickel-containing hydrogenases are inhibited by acetylene with the (NiFe) hydrogenase being 10-50 fold more sensitive than the (NiFeSe) hydrogenase. In addition the Ni(III) EPR signal (g approximately 2.3) of the "as isolated" (NiFe) hydrogenase was significantly decreased in intensity upon exposure to acetylene.     

Inhibited enzyme electrodes. Part 3: A sensor for low levels of H2S and HCN

It is shown that an inhibited enzyme electrode, using cytochrome oxidase, will respond to H₂S, HCN and azide ion. For all three inhibitors the kinetics of the inhibition and recovery processes have been analysed using the theoretical model presented previously (Albery et al., 1990a). Rearrangement of the differential equation describing inhibition and the development of the necessary software has enabled us to obtain values of the concentration of inhibitor in a matter of seconds after exposure of the sensor. The sensor will measure concentrations of H₂S down to 1 ppm in the gas phase and concentrations of HCN and azide ion down to 0·4 μmol dm⁻³ in the solution     

国产磨芋属的染色体核型报道(1)

本文报道了磨芋属(Amorphophallus Blume)六个种的染色体数目和核型,其中5个种属于首次报道。其核型公式如下: 1.滇磨芋 K(2n)=2x=26=26m.2.磨芋 K(2n)=2x=26=26m.3.攸落磨芋K(2n)=2x=26=22m(2SAT)+4sm.(2SAT).4.西盟磨芋 K(2n)=2x=26=20m+4sm+2st.5.勐海磨芋 K(2n)=2x=26=22m+4sm.6.白磨芋 K(2n)=2x=26=20m(2SAT)+6sm。     

植物单盐毒害和离子拮抗机理研究Ⅰ.单盐和混合盐对植物原生质体膜某些特性、超氧物歧化酶和过氧化氢酶活性的影响

单盐(KCl, CaCl_2或MgCl_2)和混合盐(KC_1+CaCl_2或KCl+MgCl_2)对植物原生质体完整率、存活率和膜透性等均有明显影响。K~+、Ca~(2+)或Mg~(2+)等单种阳离子明显降低原生质体膜完整率和存活率而增加其物质渗漏量,其中以单价阳离子K~+的影响为甚。上述单种阳离子还明显降低小麦幼叶超氧物歧化酶(SOD)和过氧化氢酶活性。只有由单价和二价阳离子组成的平衡混合盐才能使原生质体维持较高的完整率、存活率和较正常的膜透性.并能使细胞维持较高的SOD和过氧化氢酶活性。 认为单盐毒害机理可能是首先引起细胞膜发生不正常的膜相变或细胞累积较多的有害氧自由基,引起膜脂发生过氧化或脱酯化而破坏膜结构。在离子平衡混合盐作用下,膜系才能维持正常液晶相,具有较高活性的SOD和过氧化氢酶等生物保护性酶系是离子拮抗作用之原因。     

中国3个地区汉族人群补体C6的遗传多态性研究

运用聚丙烯酰胺凝胶等电聚焦(PAGIF)和免疫吸引技术,研究了3个地区汉族人群的C6多态性。得到的基因频率如下:漳州市——C6*A:0.4634、C6*B:0.5000、C6*R:0.0366(C6*B2:0.0317);成都市——C6*A:0.4975,C6*B:0.4484,C6*R:0.0545(C6*B2:0.0395);哈尔滨市——C6*A:0.4708,C6*B:0.5219,C6*R:0.0073(C6*B2:0.0073)。蒙古人种的C6*A频率一般都低于0.5,高加索人种的C6*A频率一般都高于0.6。黑人则介于两者之间。蒙古人种与高加索人种的另一个区别在于前者的C6*B2频率在0.03到0.07之间,而后者几乎没有C6*B2。     

Endurance at intermediate swimming speeds of Atlantic mackerel, Scomber scombrus L., herring, Clupea harengus L., and saithe, Pollachius virens L.

Endurance and swimming speed were measured in mackerel, herring and saithe when they were induced by the optomotor response to swim at prolonged speeds along a 28-m circular track through still water in a 10-m diameter gantry tank. The maximum sustained swimming speed ( U _ms was measured as body lengths per second ( b.l.s ⁻¹) for each species and for saithe of different size groups. Herring with U _ms of 4.06 b.l.s ⁻¹ (25.3 cm, 13.5°C) were the fastest, mackerel U _ms was 3.5 b.l.s ¹ (33 cm, 11.7°C) and saithe (14.4°C) showed a size effect where U _ms at 25 cm was 3.5 b.l.s ¹ and at 50 cm 2.2 b.l.s ¹. When swimming at speeds higher that U _ms, all three species showed reduced endurance as speed increased. How the curved track reduces the swimming speed is discussed.     

蛋白和酯酶电泳在根霉鉴定上的应用

对根霉(Rhizopus)属的十个种或变种共二十四株菌的菌体可溶性蛋白和酯酶同工酶进行了电泳的研究得到对这个属分类上更多的依据.在严格控制培养,提取和电泳条件的情况下,同一株菌不同批次所得菌体蛋白电泳图谱有较好的重复性.在相同的条件下,每个种的根霉有各自特征性蛋白图谱,种内不同菌株的蛋白图谱和酯酶酶谱基本相同.特别是形态特征明显、分类地位明确的种,种内各株的图谱也较一致,如R. stolonifer;与R.circinans.在确定新变种R. delemar var. latoapicalis时,电泳图谱与R.delemar var.delema:有明显不同,起到了佐证作用.因此认为,蛋白图谱与酯酶酶谱相辅相成,在根霉种的分类中是一有效的辅助手段.     

中国人线粒体DNA的八种限制酶图及其电镜结构

尽管Anderson等人(1981)已测定了人mtDNA的全部序列,但还不能全面地反映整个人类mtDNA核苷酸序列的情况。因此,在具有代表特征的中国人mtDNA序列被测定之前,为了开展对中国人mtDNA的遗传学研究,笔者构建了中国人mtDNA的8种限制酶图。并通过电镜技术对mtDNA进行了研究,发现了一种周长为2μm的小环状DNA,推测它可能在核DNA和mtDNA之间的信息传递或衰老发生中起到某些作用。