Human T-cell gamma genes contain N segments and have marked junctional variability

The gamma-chain genes are encoded by immunoglobulin-like gene segments in germline DNA which rearrange during the somatic development of T cells to form an active gene. The protein produced by these genes has not been identified and the diversity of the proteins that the genes can express has not been determined. We expect that the diversity of expressed gamma-chains is produced by the same three mechanisms that produce diversity of other immunoglobulin-like genes: (1) germline variable (V) and joining (J) region repertoires; (2) somatic mutation; and (3) junctional diversity. To define the contribution of each of these mechanisms to the generation of gamma-chain diversity, several gamma-chain complementary clones and rearranged gamma-chain genes have been characterized. Most of these clones seem to encode a defective gamma-chain, the variable- and constant-region portions being joined such that they would not be translated in the same reading frame. Here we report that the germline J-region diversity of the human T-cell gamma-chain is very limited and that somatic mutation does not contribute to the diversity of the gamma-chains encoded by the cloned segments. However, the junctional diversity of these gamma-chain genes is extensive. We suggest that N sequences (template-independent sequences) have been inserted enzymatically into all of the gamma-chain genes characterized.     

Establishment of idiotypic helper T-cell repertoires early in life

Immunoglobulin variable-region (V) genes, it is now recognized, do not encode specific receptors for T lymphocytes. Classical observations on T-cell expression of immunoglobulin idiotypes had remained unexplained until recent experiments showed that immunoglobulin idiotypes expressed by T lymphocytes in normal mice are absent in cells of the same specificity isolated from donors whose B-cell system has been suppressed by administration of anti-mu antibodies from birth. This observation provided evidence for the 'learning' of T-cell idiotypes from the B-cell/antibody system and, therefore, for the importance of idiotypic network interactions in the selection of available lymphocyte repertoires before antigenic challenge. Previously described influences of B cells and/or antibodies on the T-helper (Th) cell compartment would appear to operate at the level of clonal repertoires by complementarities with defined immunoglobulin idiotypes. Other authors, however, had previously shown the striking stability of T-cell idiotype expression in chimaeric animals reconstituted with T and B cells originating from donors showing differential idiotype expression. We have now investigated this apparent discrepancy and present here results demonstrating that immunoglobulin-dependent selection of T-cell (idiotypic) repertoires only operates for the first 3 weeks of life.     

Binding activities of a repertoire of single immunoglobulin variable domains secreted from Escherichia coli

In antibodies, a heavy and a light chain variable domain, VH and VL, respectively, pack together and the hypervariable loops on each domain contribute to binding antigen. We find, however, that isolated VH domains with good antigen-binding affinities can also be prepared. Using the polymerase chain reaction, diverse libraries of VH genes were cloned from the spleen genomic DNA of mice immunized with either lysozyme or keyhole-limpet haemocyanin. From these libraries, VH domains were expressed and secreted from Escherichia coli. Binding activities were detected against both antigens, and two VH domains were characterized with affinities for lysozyme in the 20 nM range. Isolated variable domains may offer an alternative to monoclonal antibodies and serve as the key to building high-affinity human antibodies. We suggest the name 'single domain antibodies (dAbs)' for these antigen binding demands.     

六品系猪SLA-2多肽结合区分子结构差异研究

为研究我国饲养的不同品系猪sLA_2抗原多肽结合区分子结构差异,设计引物,克隆了六品系猪SLA-2基因cDNA全长序列,用分子生物学软件分析其基因特征,比较各品系猪SLA-2分子结构差异,并通过同源模建显示变异住点的空间位置．结果表明,六品系猪SLA-2cDNA全长为1119bp,其中3-1097为编码区,共编码364个氨基酸,分别在第125,188,227,283位置出现半胱氨酸残基,含有2对链内二硫键．六品系猪SLA-2胞外区氨基酸差异主要集中在α1区的62-70及77-82和口2区的143-156．同源模建显示,这些变异位点均位于SLA-2多肽结合区的口螺旋结构上,推测可能与动物的抗病毒免疫特性有关．可为猪品系的改良及抗病毒免疫研究提供参考．     

求解波动方程混合问题的曲线积分法

传统的求解一维波动方程混合问题的方法是分离变量法,进而求出该问题的Fourier级数解.本文首先用特征线将求解区域分割成若干个小区域,然后在每个小区域内用曲线积分法求出该问题的解,最终给出该问题在求解区域内解的显式表达式.     

基于区间相容技术与GA的测试数据自动生成方法

针对测试数据自动生成完全依赖约束集求解问题（Constraint Solving Problem，CSP）进行求解会导致耗时较大甚至求解不出最终测试用例，以及采用动态GA算法又无法确定变量的最初论域空阃，首次将基于CSP求解与GA的动态算法进行了有机结合，摒弃了二者固有的缺陷，吸取了静态算法对变量论域空间削减速度快的优点。采用eBox区间相容削减标准，过滤变量的论域空间，并在经过削减的空间上采用GA搜索算法自动产生测试数据，应用常变量的逆向推导技术、表达式直接遗传等技术，大幅度地提高了测试数据的生成速度。     

一种新的变换域变步长批处理LMS算法及其应用

将变换域LMS算法和变步长LMS算法及批处理LMS算法相结合,提出了一种新的变换域变步长批处理LMS自适应算法,该算法融合了前面3种算法的优点,可以有效地降低输入信号的自相关程度,克服了固定步长因子所导致算法在快的收敛速度和较低的稳态误差之间存在的矛盾,并且实时性较好。计算机仿真结果表明该算法具有更快的收敛速度和更小的失调噪声,可以有效地应用于自适应收发隔离系统。     

菠菜转录因子MYB基因家族的鉴定及表达分析

利用生物信息学手段鉴定了76个具有典型R结构的菠菜转录因子（Spinacia oleracea） MYB,其中包括72条R2R3-MYB基因（2R-MYB）和4条R1R2R3-MYB基因（3R-MYB）。通过生物信息学对菠菜MYB转录因子家族成员的理化性质、染色体定位、结构域序列保守性和系统进化关系进行了分析,结果表明：菠菜MYB家族有32个基因位于染色体正链,另外44个基因位于染色体反链;MYB的DNA结合域中的保守域主要位于两个R重复序列的第二和第三螺旋之间,结合域中每个R重复的第一和第二色氨酸之间的氨基酸序列相对不保守;根据菠菜、拟南芥及甜菜的MYB家族系统进化关系可以推测,菠菜MYB家族中56个成员可以按功能划分为4类,在菠菜的生长发育过程中可能起着重要的调节作用,其余成员中有7个MYB基因可能参与菠菜响应氮素浓度的氮素利用及生长发育进程。     

精子载体法转基因动物研究进展

精子作为基因的载体制作转基因动物,以其简单、高效和广泛适用等特点而吸引众多的研究小组在不同水平上进行研究。本就四个方面：不同种动物精子与ＤＮＡ结合的研究;精子与ＤＮＡ结合的调控机制;与精子结合的ＤＮＡ的定位及去向;利用精子载体法制作转基因动物的研究,对他们的研究加以系统综述。     

改进的实码加速遗传算法

对实码加速遗传算法(RAGA)8个步骤的局部参数进行修改,再对最后一次加速收缩后的区间用标准遗传算法(SGA)进行精细搜索。经过实例证明,改进后的算法计算机运行的次数减少,并且精度也得到提高。另外,对加速后的区间产生偏向最优点一侧的概率做了理论上的探讨,提出了把区间端点值重新赋给2个个体参加下一轮搜索。这样处理后避免舍去上次搜索的最优值,在一定程度上避免了某个变量的搜索区间在最优值一侧发生偏移。     

Chromosomal clustering of muscle-expressed genes in Caenorhabditis elegans

Chromosomes are divided into domains of open chromatin, where genes have the potential to be expressed, and domains of closed chromatin, where genes are not expressed. Classic examples of open chromatin domains include 'puffs' on polytene chromosomes in Drosophila and extended loops from lampbrush chromosomes. If multiple genes were typically expressed together from a single open chromatin domain, the position of co-expressed genes along the chromosomes would appear clustered. To investigate whether co-expressed genes are clustered, we examined the chromosomal positions of the genes expressed in the muscle of Caenorhabditis elegans at the first larval stage. Here we show that co-expressed genes in C. elegans are clustered in groups of 2-5 along the chromosomes, suggesting that expression from a chromatin domain can extend over several genes. These observations reveal a higher-order organization of the structure of the genome, in which the order of the genes along the chromosome id correlated with their expression in specific tissues.     

大豆bHLH转录因子家族成员的进化及功能分化研究

碱性螺旋-环-螺旋蛋白(basic Helix-Loop-Hleix,bHLH)转录因子家族是动植物中最大的转录因子家族之一,主要由碱性氨基酸区域和螺旋-环-螺旋区域组成,在动植物生长发育和胁迫应答反应中发挥着重要作用.本研究通过对大豆全基因组生物信息学分析和分子生物学研究手段,深入研究了大豆bHLH基因家族的进化机制,同时探讨了该基因家族在大豆中的功能分化.结果表明,大豆中含有340个非冗余的bHLH基因家族成员,通过对这些成员的Pfam蛋白结构域、Motif组成和系统进化关系的分析,将这些成员分为15组共24个亚家族,在大豆20条染色体上呈现不均匀分布.bHLH理化性质差异较大,编码的大豆氨基酸数量为91～815aa,相对分子量为10 273.88～91 300.38,理论等电点为4.56～10.40;碱性氨基酸区含有His5-Glu9-Arg13保守序列,与靶基因结合有关,HLH区含有Arg23和Arg55,与形成二聚体有关,同时含有5种保守元件.多数成员在大豆根以及花发育的5个时期中具有组织表达特异性,不同基因表达量差异较大.     

用状态变量法研究轴承-转子系统稳定性

在计算轴承－ 转子系统的稳定性和轴心轨迹时,为克服特征根法、Ｆｏｕｒｉｅｒ 级数法等计算方法的局限性,提出了用状态方程的时域分析法计算流体润滑轴承在位移扰动、冲击载荷和不平衡激励等典型扰动下的轴心轨迹和判断稳定性的方法,根据当前时刻的状态变量值,只要进行一次矩阵乘法即可得到下一时刻的状态变量值,具有不受步长大小的限制而保持较高的计算精度。同时还讨论了小扰动理论的使用条件。     

Progress in crystallization of major histocompatibility complex class I in vertebrates

The major histocompatibility complex(MHC)of proteins that exists in all vertebrates is encoded by a cluster of genes associated with the immune response and related functions.MHC is divided into MHC I,II,and III;MHC I is involved in antigenic presentation,binding T cell receptors,and leading ultimately to specific cellular immune responses.The complicated functions of MHC I are determined by the nature of the complex.The crystal structure of MHC I has been solved for many animals,revealing the relationship between spatial structure and function.MHC I consists of an a heavy chain and a b2m light chain,both ligated non-covalently to a complex when a peptide is bound to the antigenic-binding groove.The a heavy chain is divided into an extracellular domain,a transmembrane domain,and an intracellular domain.The extracellular domain consists of sub-regions a1,a2,and a3.The a1 and a2 together form the antigenic-binding groove and bind antigenic peptides with 8–10 amino acid residues.MHC I can form a stable spatial structure;however,it should be noted that there are differences in the structure of MHC I among animal species,including anchored amino acids in binding peptides,binding sites,molecular distance,crystallization conditions,etc.Here,progress in determination of the crystal structure of human,mouse,chicken,non-human primate,and swine MHC I is described in detail.     

市电频率的谱分析测量法

频率测量在电力工业中极具实用价值．笔者研究表明，利用相继两次DFT分析可以精确得出周期信号(如市电信号)各频率分量的频率、幅度与相位．这一方法的测量精度远优于其它方法，并可适用于一切具有分立谱线的时域变量的测量．     

聚合酶链反应法扩增免疫球蛋白变区基因

用异硫氰酸胍抽提抗人小细胞肺癌单克隆抗体杂交瘤细胞株2F7的总RNA,用逆转录酶合成第一链cDNA,用PCR技术扩增出351 bp的重链变区基因(V_H)和324bp轻链变区基因(V_L),分别克隆至pUCV_(NP)-PCR和pWR13载体上,经筛选和DNA序列分析研究,证实已获得了该单克隆抗体的变区基因.