Secondary structural analysis of the mRNA regions encoding the hemagglutinin cleavage site basic amino acids of the avian influenza virus H5N1 subtype samples

Here we report the codon bias and the mRNA secondary structural features of the hemagglutinin （HA） cleavage site basic amino acid regions of avian influenza virus H5N1 subtypes. We have developed a dynamic extended folding strategy to predict RNA secondary structure with RNAstructure 4.1 program in an iterative extension process. Statistical analysis of the sequences showed that the HA cleavage site basic amino acids favor the adenine-rich codons, and the corresponding mRNA fragments are mainly in the folding states of single-stranded loops. Our sequential and structural analyses showed that to prevent and control these highly pathogenic viruses, that is, to inhibit the gene expression of avian influenza virus H5N1 subtypes, we should consider the single-stranded loop regions of the HA cleavage site-coding sequences as the targets of RNA interference.     

Type II restriction endonucleases: structure and mechanism

Type II restriction endonucleases are components of restriction modification systems that protect bacteria and archaea against invading foreign DNA. Most are homodimeric or tetrameric enzymes that cleave DNA at defined sites of 4–8 bp in length and require Mg²⁺ ions for catalysis. They differ in the details of the recognition process and the mode of cleavage, indicators that these enzymes are more diverse than originally thought. Still, most of them have a similar structural core and seem to share a common mechanism of DNA cleavage, suggesting that they evolved from a common ancestor. Only a few restriction endonucleases discovered thus far do not belong to the PD...D/ExK family of enzymes, but rather have active sites typical of other endonuclease families. The present review deals with new developments in the field of Type II restriction endonucleases. One of the more interesting aspects is the increasing awareness of the diversity of Type II restriction enzymes. Nevertheless, structural studies summarized herein deal with the more common subtypes. A major emphasis of this review will be on target site location and the mechanism of catalysis, two problems currently being addressed in the literature.Received 15 November 2004; accepted 9 December 2004     

Menadione-induced apoptosis and the degradation of lamin-like proteins in tobacco protoplasts

Detection of stereotypic hallmarks of apoptosis during cell death induced by menadione, including DNA laddering and the formation of apoptotic bodies, is reported. Comet assay and the TdT-mediated dUTP nick end labelling (TUNEL) procedure were also performed to detect DNA fragmentation. Inhibition of DNA fragmentation by Ac-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO) and phenylmethylsulfosyl (PMSF) implicated the involvement of caspase-like proteases in menadione-induced apoptosis in plants. We further studied the cleavage of lamin-like proteins during apoptosis in menadione-treated tobacco protoplasts. In animals, it has been reported that the solubilization of nuclear lamina and lamin degradation occurs during apoptotic cell death. However, little is known about the fate of lamins in apoptotic plant cells. Our study provided evidence that lamin-like proteins degraded into 35-kDa fragments in tobacco protoplasts induced by menadione, and this preceded DNA fragmentation. The results thus indicated that proteolytic cleavage of nuclear lamins was also conserved in programmed cell death in plants. Received 16 November 1998; received after revision 21 December 1998; accepted 23 December 1998     

我国罕见的有色宝石矿物——透视石

本文报导了作者对新近在我国发现的透视石所做的测定结果．在实测过程中，使用了显微硬度计、宝石显微镜、偏光显微镜、平面光删光谱仪、激光光谱仪、Ｘ射线自动衍射仪以及红外光谱仪等仪器．所得的结果补充了前人工作的不足．文中最后还对透视石的宝石学价值作了简要的评述     

四组催化体系对甲基化短梗霉多糖的还原裂解

选用了四组催化体系，并以不同的配比对甲基化短梗霉多糖进行了还原裂解，其产的用ＧＣ，ＩＲ和ＮＭＲ进行了分析测试。结果表明，用这四组催化体系对甲基化短梗霉多糖的还原裂解都能得到了予期的产品，当Ｅｔ３ＳｉＨ：ＴＭＳＯＭＳ：ＢＦ３ＯＥｔ２＝５：５：１时效果好，同时测定了短梗霉多糖的结构。     

焊缝解理断裂评定的局部法

对尜平台用钢Ａ５３７由ＬＢ５２ＮＳ焊条施焊的接头焊缝采用局部法进行了脆断评定，通过拉伸试验和有限元计算得出了Ａ５３７钢焊缝金属的局面部理参量－威布尔指数ｍ和临界解理应力σｕ，可用于结构的防断设计和安全评定。     

不同晶粒尺寸C-Mn钢低温韧性的研究

对不同晶粒尺寸C-Mn钢低温缺口及裂纹断裂韧性进行了研究。结果发现:在-196～-30℃范围内,细晶钢的缺口断裂韧性显著高于粗晶钢;而在-110℃时粗晶钢裂纹断裂韧性接近或反而高于细晶钢,前者的平均值明显高于后者。粗晶钢最低韧性试样启裂点距预裂纹的距离小于细晶钢而韧性却高于细晶钢,从而否定了粗晶裂纹断裂韧性商是由于其具有大的特征距离(RKR模型)的观点。在缺口试样中细晶钢的σ_f~*/σ_(?)高于粗晶钢,而在裂纹试样中,细晶的σ_f~*/σ_(?)接近戏反而低于粗晶,这是粗、细晶粒钢缺口及裂纹断裂韧性变化不一致的主要原因,也说明σ_f~*/σ_(?)是一个有价值的韧性参量。     

水杨醛甘氨酸Schiff碱铜配合物的合成、结构、磁性及其化学核酸酶活性研究

合成了一个水杨醛甘氨酸Schiff碱铜配合物.X-射线单晶结构分析表明,铜离子通过配体羧基氧桥联形成一个三维的孔洞结构.采用电子吸收光谱、荧光光谱、电化学、凝胶电泳等方法,研究了配合物与DNA的相互作用.化学核酸酶作用机理研究表明,超氧阴离子自由基参与氧化断裂DNA反应.     

有机胺存在下烃基卤化锡与巯基乙酸Sn—Ph键断裂反应机理研究

研究了在有机胺存在下烃基卤化锡与巯基乙酸的反应特性.烃基卤化锡中烃基的种类和数目对产物结构有很大的影响,当三烃基卤化锡中含有苯基时,得到了Sn—Ph键断裂产物.对Sn—Ph键断裂反应机理进行了推理和验证.