黄芪有效成分对氧自由基清除作用的ESR研究

用电子自旋共振技术研究了黄芪总黄酮(TFA)、黄芪总皂甙(TSA)和黄芪总多糖(TPA)对次黄嘌呤／黄嘌呤氧化酶体系产生的超氧阴离子自由基和H₂O₂－Fe²⁺体系产生的羟自由基的清除作用．结果表明,这3种成分均有清除氧自由基的作用;对超氧阴离子自由基的清除效能大于对羟自由基的清除作用;其作用强度依次为TFA＞TSA＞TPA．结果提示清除氧自由基可能是黄芪抗衰老的主要机理之一,TFA和TSA是黄芪抗氧化作用的主要药理活性成分．     

胁迫处理对林生山黧豆蛋白质多肽及其含量的影响

应用二维电泳技术,分析了经水分胁迫（ＰＥＧ）、盐分胁迫（ＮａＣｌ）和热激（４０℃）处理后林生山黧豆（ＬａｔｈｙｒｕｓｓｙｌｖｅｓｔｒｉｓＬ．）体内蛋白质多肽及其含量的变化。有些蛋白质经ＰＥＧ、ＮａＣｌ和热激处理后可以产生相同的变化。两种不同的胁迫因子对某些蛋白质的影响有一定的共同性。特定的胁迫条件可以造成特定的影响。不同胁迫因子对同一蛋白质多肽可以造成不同的影响。胁迫下蛋白质的变化可能与林生山黧豆抵抗和适应胁迫条件的能力以及体内非蛋白质氨基酸的代谢有关     

萌发花生种子子叶肽链内切酶的纯化和性质

萌发花生种子子叶的肽链内切酶经硫酸铵沉淀,ＳｅｐｈａｄｅｘＧ－１００凝胶层析,ＤＥＡＥ－纤维素２３阴离子交换层析和ＤＥＡＥ－ＳｅｐｈａｄｅｘＡ５０层析,得到纯化的酶,该酶有两条同工酶,分子量分别为５８和５５ＫＤ,Ｋｍ为９．９μｍｏｌ／Ｌ,是半胱氨型肽链内切酶（ＥＣ３．４．２２）,对未萌发花生种子的贮藏蛋白没有明显降解作用．     

用多引物PCR分析γ射线引起人外周血淋巴细胞hprt基因突变

正常人外周血用~（６０）Ｃｏ射线分别进行１～８Ｇｙ照射后,在含６－ＴＧ的培养基上克隆和筛选人淋巴细胞ｈｐｒｔ突变细胞。细胞的突变频率与γ射线的照射剂量呈正相关．获得４２个ｈｐｒｔ突变细胞株,用８对ｈｐｒｔ寡核苷酸引物进行多聚酶链反应（ＰＣＲ）从细胞粗提物中分别扩增ｈｐｒｔ各个外显子,分析突变细胞的ｈｐｒｔ基因突变,约６０％（２５／４２）的ｈｐｒｔ基因突变为基因缺失,其中１３个突变是ｈｐｒｔ基因全部缺失,而１２个是部分ｈｐｒｔ基因外显子缺失,约有４０％（１７／４２）的突变无明显的ＰＣＲ扩增变化．同时显示ｈｐｒｔ基因外显子的缺失突变与辐射剂量有关,实验结果提示,此方法有可能用于估计辐射剂量和进行辐射远后效果观察,进而揭示辐射致突的分子机理．     

链霉菌酪氨酸酶基因的克隆与表达

本文综述了近年来对链霉菌酪氨酸酶基因的研究。由酪氨酸酶合成黑色素是链霉菌属各个种的共同特性,并受到酪氨酸酶基因的控制。链霉菌几个种的酪氨酸酶基因已克隆到,其产黑色素的特性使之作为重要的标记基因得以广泛应用,同时,该基因在链霉菌的不同种及不同属的微生物中得到了高水平的表达。链霉菌酪氨酸酶基因表达调控的分子机制也得到较深入的研究。     

海南坡鹿对生境的选择

１９８７～１９９４年,在海南省大田自然保护区及其外围地带对坡鹿的生境选择性进行了调查,发现坡鹿对自然生境有较强的选择性。对不同的生境的选择频率为：落叶季雨林生境４７．９３％;灌木草地生境３９．１４％;有刺灌丛生境１０．７２％;人工林生境２．２１％。还对各种生境进行了评价;并提出了保护生境的对策     

Cloning and characterization of CER2, an Arabidopsis gene that affects cuticular wax accumulation.

Cuticular waxes are complex mixtures of very long chain fatty acids and their derivatives that cover plant surfaces. Mutants of the ECERIFERUM2 (cer2) gene of Arabidopsis condition bright green stems and siliques, indicative of the relatively low abundance of the cuticular wax crystals that comprise the wax bloom on wild-type plants. We cloned the CER2 gene via chromosome walking. Three lines of evidence establish that the cloned sequence represents the CER2 gene: (1) this sequence is capable of complementing the cer2 mutant phenotype in transgenic plants; (2) the corresponding DNA sequence isolated from plants homozygous for the cer2-2 mutant allele contains a sequence polymorphism that generates a premature stop codon; and (3) the deduced CER2 protein sequence exhibits sequence similarity to that of a maize gene (glossy2) that also is involved in cuticular wax accumulation. The CER2 gene encodes a novel protein with a predicted mass of 47 kD. We studied the expression pattern of the CER2 gene by in situ hybridization and analysis of transgenic Arabidopsis plants carrying a CER2-beta-glucuronidase gene fusion that includes 1.0 kb immediately upstream of CER2 and 0.2 kb of CER2 coding sequences. These studies demonstrate that the CER2 gene is expressed in an organ- and tissue-specific manner; CER2 is expressed at high levels only in the epidermis of young siliques and stems. This finding is consistent with the visible phenotype associated with mutants of the CER2 gene. Hence, the 1.2-kb fragment of the CER2 gene used to construct the CER2-beta-glucuronidase gene fusion includes all of the genetic information required for the epidermis-specific accumulation of CER2 mRNA.     

The binding motifs for Ac transposase are absolutely required for excision of Ds1 in maize

A reverse genetic system for studying excision of the transposable elementDs1 in maize plants has been established previously. In this system, theDs1 element, as part of the genome of maize streak virus (MSV), is introduced into maize plants via agroinfection. In the presence of theAc element, excision ofDs1 from the MSV genome results in the appearance of viral symptoms on the maize plants. Here, we used this system to study DNA sequences requiredin cis for excision ofDs1. TheDs1 element contains theAc transposase binding motif AAACGG in only one of its subterminal regions (defined here as the 5′ subterminal region). We showed that mutation of these motifs abolished completely the excision capacity ofDs1. This is the first direct demonstration that the transposase binding motifs are essential for excision. Mutagenesis with oligonucleotide insertions in the other (3′) subterminal region resulted in elements with either a reduced or an increased excision efficiency, indicating that this subterminal region also has an important function.     

Isoform-specific complementation of the yeast sac6 null mutation by human fimbrin.

The actin cytoskeleton is a fundamental component of eukaryotic cells, with both structural and motile roles. Actin and many of the actin-binding proteins found in different cell types are highly conserved, showing considerable similarity in both primary structure and biochemical properties. To make detailed comparisons between homologous proteins, it is necessary to know whether the various proteins are functionally, as well as structurally, conserved. Fimbrin is an example of a cytoskeletal component that, as shown by sequence determinations and biochemical characterizations, is conserved between organisms as diverse as Saccharomyces cerevisiae and humans. In this study, we examined whether the human homolog can substitute for the yeast protein in vivo. We report here that two isoforms of human fimbrin, also referred to as T- and L-plastin, can both substitute in vivo for yeast fimbrin, also known as Sac6p, whereas a third isoform, I-fimbrin (or I-plastin), cannot. We demonstrate that the human T- and L-fimbrins, in addition to complementing the temperature-sensitive growth defect of the sac6 null mutant, restore both normal cytoskeletal organization and cell shape to the mutant cells. In addition, we show that human T- and L-fimbrins can complement a sporulation defect caused by the sac6 null mutation. These findings indicate that there is a high degree of functional conservation in the cytoskeleton, even between organisms as diverse as S. cerevisiae and humans.