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41.
Metabolic labelling by [14C]palmitic acid showed that growth of Streptococcus mutans LT11 in raffinose, an inducer of the msm operon, resulted in increased production of a 45-kDa lipoprotein corresponding to MsmE, which is believed to be a sugar-binding protein. MsmE was also labelled when an msmE clone was expressed in Escherichia coli. The presence of a lipid anchor on MsmE provides a likely explanation of how the sugar-binding protein component of the msm binding protein-dependent multiple sugar transport system is retained at the cell surface. 相似文献
42.
Depression of Neuronal Protein Synthesis Initiation by Protein Tyrosine Kinase Inhibitors 总被引:2,自引:1,他引:1
Abstract— Growth factors stimulate cellular protein synthesis, but the intracellular signaling mechanisms that regulate initiation of mRNA translation in neurons have not been clarified. A rate-limiting step in the initiation of protein synthesis is the formation of the ternary complex among GTP, eukaryotic initiation factor 2 (elF-2), and the initiator tRNA. Here we report that genistein, a specific tyrosine kinase inhibitor, decreases tyrosine kinase activity and the content of phosphotyrosine proteins in cultured primary cortical neurons. Genistein inhibits protein synthesis by >80% in a dose-dependent manner (10–80 μg/ml) and concurrently decreases ternary complex formation by 60%. At the doses investigated, genistein depresses tyrosine kinase activity and concomitantly stimulates PKC activity. We propose that a protein tyrosine kinase participates in the initiation of protein synthesis in neurons, by affecting the activity of elF-2 directly or through a protein kinase cascade. 相似文献
43.
Eviostachya hoegii Stockmans在中国五通组的首次发现 总被引:2,自引:0,他引:2
首次描述了Eviostachya hoegii Stockmans的营养部分,通过大量标本的观察,修订了前人有关其生殖部分和解剖部分的描述,并对其生殖部分进行了复原.同意Emberger(1968)的观点,将其归于Eviostachyrales中. 相似文献
44.
Hindered diffusion of high molecular weight compounds in brain extracellular microenvironment measured with integrative optical imaging. 总被引:4,自引:0,他引:4 下载免费PDF全文
This paper describes the theory of an integrative optical imaging system and its application to the analysis of the diffusion of 3-, 10-, 40-, and 70-kDa fluorescent dextran molecules in agarose gel and brain extracellular microenvironment. The method uses a precisely defined source of fluorescent molecules pressure ejected from a micropipette, and a detailed theory of the intensity contributions from out-of-focus molecules in a three-dimensional medium to a two-dimensional image. Dextrans tagged with either tetramethylrhodamine or Texas Red were ejected into 0.3% agarose gel or rat cortical slices maintained in a perfused chamber at 34 degrees C and imaged using a compound epifluorescent microscope with a 10 x water-immersion objective. About 20 images were taken at 2-10-s intervals, recorded with a cooled CCD camera, then transferred to a 486 PC for quantitative analysis. The diffusion coefficient in agarose gel, D, and the apparent diffusion coefficient, D*, in brain tissue were determined by fitting an integral expression relating the measured two-dimensional image intensity to the theoretical three-dimensional dextran concentration. The measurements in dilute agarose gel provided a reference value of D and validated the method. Values of the tortuosity, lambda = (D/D*)1/2, for the 3- and 10-kDa dextrans were 1.70 and 1.63, respectively, which were consistent with previous values derived from tetramethylammonium measurements in cortex. Tortuosities for the 40- and 70-kDa dextrans had significantly larger values of 2.16 and 2.25, respectively. This suggests that the extracellular space may have local constrictions that hinder the diffusion of molecules above a critical size that lies in the range of many neurotrophic compounds. 相似文献
45.
鼎湖山自然林豆科固氮植物资源的调查研究 总被引:3,自引:1,他引:2
本文在调查鼎湖山自然林木本豆科植物结瘤固氮的基础上,参阅了国内外有关豆科植物结瘤固氮的主要文献,研究了鼎湖山自然林木本豆科植物的固氮资源。结果得出鼎湖山自然林中常见的木本豆科植物共有41种,其中乔木15种,灌木6种,木质藤本20种;有结瘤固氮特性的26种,其中乔木11种,灌木5种,木质藤本10种;经初步调查未见根瘤的6种,其中乔木2种,灌木1种,木质藤本3种;未调查的9种,其中乔木2种,木质藤本7种。本研究结果为鼎湖山木本豆科固氮植物资源的保护、管理和开发利用提供了科学论据,在理论和应用方面均有重要意义。 相似文献
46.
47.
Crevice-forming mutants in the rigid core of bovine pancreatic trypsin inhibitor: crystal structures of F22A, Y23A, N43G, and F45A. 总被引:4,自引:4,他引:0 下载免费PDF全文
A. T. Danishefsky D. Housset K. S. Kim F. Tao J. Fuchs C. Woodward A. Wlodawer 《Protein science : a publication of the Protein Society》1993,2(4):577-587
Crystal structures of four mutants of bovine pancreatic trypsin inhibitor (F22A, Y23A, N43G, and F45A), engineered to alter their stability properties, have been determined. The mutated residues, which are highly conserved among Kunitz-type inhibitors, are located in the rigid core of the molecule. Replacement of the partially buried bulky residues of the wild-type protein with smaller residues resulted in crevices open to the exterior of the molecule. The overall three-dimensional structure of these mutants is very similar to that of the wild-type protein and only small rearrangements are observed among the atoms lining the crevices. 相似文献
48.
Rukui Zhu Yu Liang Huajian Luo Huishan Cao Yi Liu Shan Huang Qi Xiao 《Journal of molecular recognition : JMR》2023,36(1):e3000
In this work, binding interactions of artemisinin (ART) and dihydroartemisinin (DHA) with human serum albumin (HSA) and bovine serum albumin (BSA) were investigated thoroughly to illustrate the conformational variation of serum albumin. Experimental results indicated that ART and DHA bound strongly with the site I of serum albumins via hydrogen bond (H-bond) and van der Waals force and subsequently statically quenched the intrinsic fluorescence of serum albumins through concentration-dependent manner. The quenching abilities of two drugs on the intrinsic fluorescence of HSA were much higher than the quenching abilities of two drugs on the intrinsic fluorescence of BSA. Both ART and DHA, especially DHA, caused the conformational variation of serum albumins and reduced the α-helix structure content of serum albumins. DHA with hydrophilic hydroxyl group bound with HSA more strongly, suggesting the important roles of the chemical polarity and the hydrophilicity during the binding interactions of two drugs with serum albumins. These results reveal the molecular understanding of binding interactions between ART derivatives and serum albumins, providing vital information for the future application of ART derivatives in biological and clinical areas. 相似文献
49.
50.
İncili Çınar Yiğit Arslan Büşra Çelik Esra Nurten Yer Ulu Ferhat Horuz Erdoğan Baloglu Mehmet Cengiz Çağlıyan Ebrar Burcu Gamze Bayarslan Aslı Ugurlu Altunoglu Yasemin Celik 《Protoplasma》2023,260(2):509-527
Protoplasma - Watermelon and melon are members of the Cucurbitaceae family including economically significant crops in the world. The expansin protein family, which is one of the members of the... 相似文献