黄芪总黄酮对DNA损伤防护作用的研究

用DNA解旋荧光检测法(FADU)研究了黄芪总黄酮(TFA)对γ射线和H₂O₂所致V79细胞DNA链断裂的防护作用. 结果表明TFA对这两种损伤因子所致的DNA损伤均有不同程度的防护作用, 当TFA浓度达到0.4g/L和0.6g/L时, 分别对H₂O₂和γ射线所致的损伤有保护作用(P<0.05), 而浓度增至0.8g/L和1.2g/L时, 分别对两种因素所致的DNA链断裂损伤有非常显著的防护效果(P<0.01), 对H₂O₂的防护效果优于对γ射线.     

用快速琼脂糖层析纯化磷酸甘油酸激酶及磷酸甘油醛脱氢酶

研究了用快速琼脂糖离子交换层析(DEAE—Fast Flow sepharose)结台PEG 4000／Reppal PES双水相体系从黄豆中分离纯化磷酸甘油酸激酶(PGK)及磷酸甘油醛脱氢酶(GAPDH)。控制床层高度(10～20cm),径向放大具有压降低的优点．设计多点进料取代传统的中心管进料,解决了径向流场不均匀的问题。GAPr)H的总收率及纯化倍数分别为58％和144,PGK的总收率及纯化倍数分别为41％和44。工艺成本为2．92美元／ku GPADH,具有一定的实用价值。     

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．     

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。     

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.     

Thermotolerance induced by heat shock in Chlorella

Thermotolerance in cultures of Chlorella zofingiensis was induced by heat shock treatment at supraoptimal temperatures (40and 45 °C for 30 min). Thermotolerance was assayed by two methods: the survival of the cells at 70 °C and the growth of diluted cultures at 35 and 45 °C. A culture without heat shock treatment was unable to grow at 45 °C. According to eletrophoretic analyses, the synthesis of proteins of 95, 73, 60, 43 and 27 kDa was induced by heat shock treatment. The large molecular weight proteins (95, 73, 60 and43 kDa) were present in non-heat treated cells, but the heat shock treatment increased their quantity in cells. The synthesis of a low molecular weight protein (27 kDa) was induced by heat shock treatment. The induced thermotolerance could be inhibited by the presence of an 80S ribosomal translation inhibitor, cycloheximide(CHI). The first 12 amino acid residues from the N-terminus of the27 kDa heat shock induced protein are Val-Glu-Trp-Try-Gly-Pro-Asn-Arg-Ala-Lys-Phe-Leu. This revised version was published online in August 2006 with corrections to the Cover Date.