排序方式: 共有7条查询结果,搜索用时 15 毫秒
1
1.
The stability constants of the mixed ligand complexes of L-dopa, L-tyrosine, L-phenylalanine, and dopamine with copper(II) and nickel(II) ions and with 2,2'-bipyridyl and 1,10-phenanthroline were determined pH-metrically at 25 degrees C and an ionic strength of 0.2 mol/dm3 (KCl). Spectral studies were made to establish the binding mode of the ambidentate L-dopa in the ternary complexes. In contrast with the aromatic (N,N) donor atoms, the (O,O) binding mode of L-dopa is particularly favored in its ternary systems with copper(II) and nickel(II); thus, even at physiological pH there is a very considerable formation of (O,O)-bound mixed ligand complexes containing a free amino acid side-chain. Numerous binary transition metal-L-dopa complexes and the ternary complexes formed with various B ligands have been evaluated from a coordination chemistry aspect, with regard to the possibility of their therapeutic application in the treatment of Parkinson disease. 相似文献
2.
L.R. Barran J.Y. Daoust J.L. Labelle W.G. Martin H. Schneider 《Biochemical and biophysical research communications》1974,56(2):522-528
Light of wavelengths above 400 nm inactivated several active transport systems in E. coli ML 308. Rates of inactivation for uptake of threonine, glycine, leucine and methionine were similar and differed from those for methyl thio-β-D-galactoside and phenylalanine. These differential effects indicate that inactivation of the threonine, glycine, leucine and methionine systems is linked to a common photochemical lesion differing from that involved in the inactivation of the methyl thio-β-D-galactoside and phenylalanine systems. These lesions may serve as labels to identify molecules involved in transport or energy coupling processes. 相似文献
3.
4.
Amihai Karniel Devid Mrusek Wieland Steinchen Orly Dym Gert Bange Eitan Bibi 《Journal of molecular biology》2018,430(11):1607-1620
Much of our knowledge on the function of proteins is deduced from their mature, folded states. However, it is unknown whether partially synthesized nascent protein segments can execute biological functions during translation and whether their premature folding states matter. A recent observation that a nascent chain performs a distinct function, co-translational targeting in vivo, has been made with the Escherichia coli signal recognition particle receptor FtsY, a major player in the conserved pathway of membrane protein biogenesis. FtsY functions as a membrane-associated entity, but very little is known about the mode of its targeting to the membrane. Here we investigated the underlying structural mechanism of the co-translational FtsY targeting to the membrane. Our results show that helices N2–4, which mediate membrane targeting, form a stable folding intermediate co-translationally that greatly differs from its fold in the mature FtsY. These results thus resolve a long-standing mystery of how the receptor targets the membrane even when deleted of its alleged membrane targeting sequence. The structurally distinct targeting determinant of FtsY exists only co-translationally. Our studies will facilitate further efforts to seek cellular factors required for proper targeting and association of FtsY with the membrane. Moreover, the results offer a hallmark example for how co-translational nascent intermediates may dictate biological functions. 相似文献
5.
鲤鱼线粒体tRNA~(phe)基因的核酸序列已被测定。在鲸、人、爪蟾、牛、小鼠、鸡和鲤鱼中对此基因序列比较发现在D茎存在一个奇怪的保守结构,然而D茎在其余种类的已经测定的脊椎动物线粒体tRNA基因和细胞质tRNA基因中是极不保守的。这一保守结构包含有13bp碱基,我们将此保守区前7个碱基与真核生物RNA PolⅢ识别的A区相比较,发现在此不同物种的两种序列存在部分的同源性。考虑到tRNA~(phe)基因在线粒体基因组上位于置换环区和线粒体rRNA基因编码区之间这一特殊区域内,我们推测这一奇怪的保守结构可能存在其它更为有意义的功能。 相似文献
6.
大肠杆菌aroG基因的克隆表达及与pheA、tyrB基因的串联表达 总被引:1,自引:0,他引:1
3-脱氧-2-阿拉伯庚酮糖-7-磷酸合成酶(DAHP)是苯丙氨酸合成途径中关键酶之一,在大肠杆菌中由aroG基因编码。本文用NTG诱变得到对苯丙氨酸类似物间氟苯丙氨酸(mFP)和对氟苯丙氨酸(pFP)有抗性的大肠杆菌突变株,采用聚合酶链反应(PCR)扩增得到了aroG基因,在大肠杆菌中进行了表达。结果表明,该基因能在λ噬菌体的pR启动子驱动下得到表达,在SDS-聚丙烯酰胺凝胶电泳图上出现清晰的条带,酶的比活提高了1.7倍。在pheA(编码分枝酸变位酶CM和预苯酸脱水酶PD)、tyrB(编码苯丙氨酸转氨酶PAT)基因克隆、串联克隆和表达完成的基础上,将aroG基因和pheA、tyrB基因以aroG-pheA-tyrB的顺序三基因串联到表达载体进行表达,酶活测定结果表明,三个基因都能在λ噬菌体的pR启动子驱动下表达,与对照菌株相比,酶比活分别提高了1.7倍、13.9/7.8倍和2.3倍。 相似文献
7.
1