非天然氨基酸及非天然蛋白合成的研究进展

非天然氨基酸是天然氨基酸的衍生物,其具有重要的生理和药理功能.由非天然氨基酸合成的非天然蛋白同样具有特别的功能与活性.非天然氨基酸插入蛋白质中的研究为新型生物材料和蛋白质药物等的合成和应用提供了新的指导方向.基于此,本文综述了非天然氨基酸的生物合成方法,分析了非天然氨基酸生物合成目前存在的难点,总结了非天然氨基酸插入蛋...     

氨基酸的分子结构与遗传密码简并及二维集合分类

根据氨基酸遗传密码子的简并程度,可将64个遗传密码子分为高简并度类（3,4,6度简并组）和低简并度类（1,2度简并组）两大类。高简并度类有9个氨基酸,其分子量比较小,等电点的分布比较集中。低简并度类有11个氨基酸,其分子结构比较复杂,参考Taylor对氨基酸特性的分类图,本文提出以分子量（M）及等电点（P）作为氨基酸的化学特性坐标,作出其二维集合MP分类图,MP分类图可以反映出氨基酸的各种属性,如分子量的大小,简并度的高低,极性与非极性、带电荷或不带电荷,疏水性与亲水性,以及氨基酸残基的种类等。根据氨基酸的分类分析,可以认为：高简并度氨基酸多数是脂烃类和羟脂烃类的氨基酸,分子量比较小,分子结构比较简单,大部分为疏子性,主要组成跨膜结构或蛋白质的结构域,可能是出现较早的氨基酸;而低简并度的氨基酸,分子结构比较复杂,分子量比较大,多数是和蛋白质功能有密切联系的基团,可能是进化出现较晚的结构。     

破译尼安德特人的遗传密码

尼安德特人是历史上人类已消失的近亲,这些来自3．8万年前尼安德特人的DNA正在改变曾一度沉寂的古生     

遗传密码扩充技术

遗传密码的扩充打破了天然生命体基因只能编码天然氨基酸的限制.遗传密码扩充技术使人们可以将具有特殊性质的非天然氨基酸通过基因表达到生物活体的蛋白质中.该文对遗传密码扩充的原理、方法及意义进行简述.     

遗传密码子进化的阶段性

密码子的起源与进化可划分为4个阶段,即：前密码子期,tRNA形成期,原密码子与有序肽同步起源期,以及密码子进化期。不同的观点,大都能在不同时期找到自己的位置,从而是互补的。在此基础上,首次将主要理论的主旨整合为一个进化过程的理论框架,基本上协调了持续了近半个世纪的确定论和偶然论之争,并且解释了密码子设定的多态性的由来。     

Analysis of synonymous codon usage bias in Chlamydia

Chlamydiae are obligate intracellular bacterial pathogens that cause ocular and sexuallytransmitted diseases,and are associated with cardiovascular diseases.The analysis of codon usage mayimprove our understanding of the evolution and pathogenesis of Chlamydia and allow reengineering of targetgenes to improve their expression for gene therapy.Here,we analyzed the codon usage of C.muridarum,C.trachomatis(here indicating biovar trachoma and LGV),C.pneumoniae,and C.psittaci using the codonusage database and the CUSP(Create a codon usage table)program of EMBOSS(The European MolecularBiology Open Software Suite).The results show that the four genomes have similar codon usage patterns,with a strong bias towards the codons with A and T at the third codon position.Compared with Homosapiens,the four chlamydial species show discordant seven or eight preferred codons.The ENC(effectivenumber of codons used in a gene)-plot reveals that the genetic heterogeneity in Chlamydia is constrained bythe G+C content,while translational selection and gene length exert relatively weaker influences.Moreover,mutational pressure appears to be the major determinant of the codon usage variation among the chlamydialgenes.In addition,we compared the codon preferences of C.trachomatis with those of E.coli,yeast,adenovirus and Homo sapiens.There are 23 codons showing distinct usage differences between C.trachomatisand E.coli,24 between C.trachomatis and adenovirus,21 between C.trachomatis and Homo sapiens,butonly six codons between C.trachomatis and yeast.Therefore,the yeast system may be more suitable for theexpression of chlamydial genes.Finally,we compared the codon preferences of C.trachomatis with those ofsix eukaryotes,eight prokaryotes and 23 viruses.There is a strong positive correlation between the differ-ences in coding GC content and the variations in codon bias(r=0.905,P<0,001).We conclude that thevariation of codon bias between C.trachomatis and other organisms is much less influenced by phylogeneticlineage and primarily determined by the extent of disparities in GC content.     

A Method for Identification of Selenoprotein Genes in Archaeal Genomes

The genetic codon UGA has a dual function: serving as a terminator and encoding selenocysteine. However, most popular gene annotation programs only take it as a stop signal, resulting in misannotation or completely missing selenoprotein genes. We developed a computational method named Asec-Prediction that is specific for the prediction of archaeal selenoprotein genes. To evaluate its effectiveness, we first applied it to 14 archaeal genomes with previously known selenoprotein genes, and Asec-Prediction identified all reported selenoprotein genes without redundant results. When we applied it to 12 archaeal genomes that had not been researched for selenoprotein genes, Asec-Prediction detected a novel selenoprotein gene in Methanosarcina acetivorans. Further evidence was also collected to support that the predicted gene should be a real selenoprotein gene. The result shows that Asec-Prediction is effective for the prediction of archaeal selenoprotein genes.     

时代与巨人

达尔文进化论的诞生至今将近一个半世纪,在这期间,枝繁叶茂的进化树替代了干瘪粗糙的分类树;抽象无形的遗传密码接管了有限的形态特征成为了人们研究生物学的利器,生物学的发展可谓日新月异。但惟有达尔文的进化论,好似巨人厚重的肩膀,承载着后来者,让我们站在一个更高的水平去探索生命世界的规律。     

对ERP非专业成员有用的遗传术语词汇表（1）

脱氧核糖核苷酸（DNA） 在多数机体里,DNA携带了主要遗传信息,一个机体的所有DNA的总合成为基因组。DNA包含一个由我们称作遗传密码的硷基亚单位组成的长链。部分DNA或基因可以复制并翻译成蛋白。DNA的其他部分为调节元件,调控基因在正确的时间编码正确数量的蛋白,因此它们控制了基因的表达。