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排序方式: 共有125条查询结果,搜索用时 15 毫秒
1.
Analysis of synonymous codon usage in H5N1 virus and other influenza A viruses   总被引:11,自引:0,他引:11  
Zhou T  Gu W  Ma J  Sun X  Lu Z 《Bio Systems》2005,81(1):77-86
In this study, we calculated the codon usage bias in H5N1 virus and performed a comparative analysis of synonymous codon usage patterns in H5N1 virus, five other evolutionary related influenza A viruses and a influenza B virus. Codon usage bias in H5N1 genome is a little slight, which is mainly determined by the base compositions on the third codon position. By comparing synonymous codon usage patterns in different viruses, we observed that the codon usage pattern of H5N1 virus is similar with other influenza A viruses, but not influenza B virus, and the synonymous codon usage in influenza A virus genes is phylogenetically conservative, but not strain-specific. Synonymous codon usage in genes encoded by different influenza A viruses is genus conservative. Compositional constraints could explain most of the variation of synonymous codon usage among these virus genes, while gene function is also correlated to synonymous codon usages to a certain extent. However, translational selection and gene length have no effect on the variations of synonymous codon usage in these virus genes.  相似文献   
2.
外来物种入侵严重威胁着乡土植物多样性并削弱了生态系统服务功能。本文基于滇西北怒江河谷植被调查的样方数据, 从群落水平研究了乡土和入侵植物多样性的空间分布格局, 以及地形、气候、人类干扰等因子对两种格局的影响。本研究共记录到外来入侵植物26种, 隶属于13科21属; 乡土植物1,145种, 分属于158科628属。沿着怒江河谷, 入侵植物物种丰富度随纬度与海拔的增加而减少; 乡土物种丰富度则随纬度增加而增加, 并在海拔梯度上呈单峰格局。运用广义线性模型分析公路边缘效应(反映生境干扰)、气候、地形和土壤等环境因素对物种丰富度分布格局的影响。等级方差分离的结果显示, 公路两侧的生境干扰对入侵种和乡土种的丰富度格局均具有首要影响。在自然环境因子中, 降水量是入侵植物丰富度的主要限制因子, 而乡土物种丰富度则主要受到地形因子尤其是坡向的影响。结构方程模型的分析结果也表明, 乡土植物和入侵植物丰富度之间的负相关关系反映了二者对环境响应的差异。本文结果支持物种入侵的资源可利用性限制假说, 并强调了人类活动对生物多样性的负面影响; 乡土植物或已较好地适应了干旱河谷气候, 但并没有显示出对外来物种入侵的抵抗作用。  相似文献   
3.
脱氧核糖核酸(Deoxyribonucleic Acid, DNA)是一种天然的信息存储介质,具有存储密度高、存储时间长、损耗率低等特点。在传统存储方式不能满足信息增长的需求时,DNA数据存储技术逐渐成为研究热点。DNA编码是用尽可能少的碱基序列无错的存储数据信息,包括压缩(尽可能少的占用空间)、纠错(无错存储)和转换(数字信息转为碱基序列)3部分。DNA编码是DNA存储中的关键技术,它的结果直接影响存储性能的优劣和数据读写的完整。本文首先介绍DNA存储的发展历史,然后介绍DNA存储的框架,其中重点介绍DNA编码技术,最后对DNA存储中的编解码技术的未来发展方向进行讨论。  相似文献   
4.
环状RNA(circular RNA,circRNA)是一类具有重要生物作用的内源性RNA,大多在可变剪接过程中通过5'端和3'端反向共价连接形成闭合环状结构.目前,环状RNA的识别策略主要分为两大类:一类方法从高通量测序(RNA-seq)数据中检测反向剪接位点,另一类直接从RNA序列中检测成环特征.由于数据本身和识别...  相似文献   
5.
Yang  Meifang  Wei  Ming  Wang  Chengjian  Lu  Yu  Jin  Wanjun  Gao  Xi  Li  Cheng  Wang  Langhong  Huang  Linjuan  Wang  Zhongfu 《Glycoconjugate journal》2020,37(2):165-174
Glycoconjugate Journal - The study of carbohydrates requires large amounts of glycans. N-Glycans can be synthesized but generating large quantities of N-glycans with diverse structures remains...  相似文献   
6.
Recent studies have implied that miRNAs act as crucial modulators for epithelial-to-mesenchymal transition (EMT). We found that miR-148a is significantly downregulated in non-small cell lung cancer (NSCLC) compared to adjacent non-cancerous lung tissues, and the downregulated miR-148a was significantly associated with lymph-node metastasis. Functional assays demonstrated that miR-148a inhibited EMT in NSCLC cells. Moreover, miR-148a decreased 3′-untranslated region luciferase activity of ROCK1 and ROCK1 protein expression. Knockdown of ROCK1 reversed EMT resembling that of miR-148a overexpression. Furthermore, ROCK1 was widely upregulated in NSCLC, and its mRNA levels were inversely correlated with miR-148a expression. These findings suggest that miR-148a acts as a novel EMT suppressor in NSCLC cells, at least in part by modulation of ROCK1.  相似文献   
7.
Three homologues of TGF-β exist in mammals as follows: TGF-β1, TGF-β2, and TGF-β3. All three proteins share high homology in their amino acid sequence, yet each TGF-β isoform has unique heterologous motifs that are highly conserved during evolution. Although these TGF-β proteins share similar properties in vitro, isoform-specific properties have been suggested through in vivo studies and by the unique phenotypes for each TGF-β knock-out mouse. To test our hypothesis that each of these homologues has nonredundant functions, and to identify such isoform-specific roles, we genetically exchanged the coding sequence of the mature TGF-β1 ligand with a sequence from TGF-β3 using targeted recombination to create chimeric TGF-β1/3 knock-in mice (TGF1Lβ3/Lβ3). In the TGF1Lβ3/Lβ3 mouse, localization and activation still occur through the TGF-β1 latent associated peptide, but cell signaling is triggered through the TGF-β3 ligand that binds to TGF-β receptors. Unlike TGF1−/− mice, the TGF1Lβ3/Lβ3 mice show neither embryonic lethality nor signs of multifocal inflammation, demonstrating that knock-in of the TGF-β3 ligand can prevent the vasculogenesis defects and autoimmunity associated with TGF-β1 deficiency. However, the TGF1Lβ3/Lβ3 mice have a shortened life span and display tooth and bone defects, indicating that the TGF-β homologues are not completely interchangeable. Remarkably, the TGF1Lβ3/Lβ3 mice display an improved metabolic phenotype with reduced body weight gain and enhanced glucose tolerance by induction of beneficial changes to the white adipose tissue compartment. These findings reveal both redundant and unique nonoverlapping functional diversity in TGF-β isoform signaling that has relevance to the design of therapeutics aimed at targeting the TGF-β pathway in human disease.  相似文献   
8.
The primary objective of this 3 years study was to determine the prevalence of porcine pathogens of the lungs of swine in swine farms in southern China. A total of 5,420 samples were collected from 200 swine farms. The bacterium that was most commonly isolated was Streptococcus suis, with 10.24 % of the samples being positive, 114 lungs (2.1 %) were positive for pseudorabies virus and 263 (4.85 %) were positive for classical swine fever virus; much lower than positive for PRRSV (15.1 %, p = 0.023) and PCV2 (13.8 %, p = 0.038). lungs that were positive for PRRSV and/or PCV-2 have significantly increased odds of being positive for any of the S. suis (9.79 vs. 0.44 %, p = 0.003).  相似文献   
9.
环状RNA是新发现的一类具有重要生物学功能的RNA。现有的环状RNA识别工具依赖高通量测序数据,因数据本身和识别方式的弊端而普遍存在准确性不足、不同方法间重复性低以及假阳性率/假阴性率高等缺点。为了解决该问题,我们搭建模型来实现不依赖于测序数据而根据序列的内在特征的环状RNA从头预测。本文选取了包括剪接位点上下游内含子的长度、A-to-I密度和Alu重复序列等100个与RNA成环相关的序列特征,建立了机器学习模型,并识别了人类基因组中的环状RNA,比较了两种机器学习方法随机森林法(RF)和支持向量机(SVM)的分类效果。结果表明,所选序列特征能有效地鉴别RNA能否成环,同时,不同序列特征对模型的分类预测能力的贡献也不同。相比于SVM方法,RF分类的效果更好。  相似文献   
10.
Gu W  Zhou T  Ma J  Sun X  Lu Z 《Bio Systems》2004,73(2):89-97
The role of silent position in the codon on the protein structure is an interesting and yet unclear problem. In this paper, 563 Homo sapiens genes and 417 Escherichia coli genes coding for proteins with four different folding types have been analyzed using variance analysis, a multivariate analysis method newly used in codon usage analysis, to find the correlation between amino acid composition, synonymous codon, and protein structure in different organisms. It has been found that in E. coli, both amino acid compositions in differently folded proteins and synonymous codon usage in different gene classes coding for differently folded proteins are significantly different. It was also found that only amino acid composition is different in different protein classes in H. sapiens. There is no universal correlation between synonymous codon usage and protein structure in these two different organisms. Further analysis has shown that GC content on the second codon position can distinguish coding genes for different folded proteins in both organisms.  相似文献   
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