β－内酰胺酶启动子C－17缺失对其强度的影响

通过酶学手段在β－内酰胺酶启动子间隔序列中造成Ｃ－１７的缺失突变,以氨苄青霉素为底物,检测突变前后β－内酰胺酶活力变化,并作了细菌的Ａｍｐ耐受性试验,实验结果表明,Ｃ－１７的缺失突变使启动子强度增加约６０％,含有突变启动子的细菌对Ａｍｐ的抗性明显增强,突变体生长的半抑制浓度为２８０μｇ／ｍｌ,而在此浓度下野生型菌体吸光度只有突变体的５０％左右,对启动子强度增加的原因进行了讨论。     

Zn2＋参与遗传调控的研究进展

Zn^2＋在遗传调控中的作用十分广泛而显著.结合新近的研究资料,着重从染色质结构与功能、核酸的生物合成、DNA的结构及构象、基因表达的调控等四个主要方面来反映Zn^2＋与遗传调控的相关性,并阐述Zn^2＋在其中发挥作用的机理.     

PV技术的计算机处理及其在树木水分关系研究中的应用

ＰＶ技术的计算机处理及其在树木水分关系研究中的应用刘建伟,刘雅荣,王世绩（中国林业科学研究院林业研究所,北京１０００９１）ＣｏｍｐｕｔｅｒＰｒｏｃｅｓｓｉｎｇｏｆＰＶＣｕｒｖｅＡｎａｌｙｓｉｓａｎｄＩｔｓＡｐｐｌｉｃａｔｉｏｎｉｎｔｈｅＲｅｓｅａｒｃ...     

触珠蛋白研究进展

触珠蛋白是一种酸性糖蛋白,属急性期反应蛋白之一,由于所含轻链类型的不同,触珠蛋白具有遗传多态性,触珠蛋白的合成和降解主要在肝脏进行,并受细胞因子、前列腺素、激素等的调节,触珠蛋白具有广泛的生物学功能,可能是一种重要的调节蛋白.     

鲑鱼生长激素基因分泌型表达质粒的构建

生长激素(GH)是动物垂体前叶分泌的一种多肽类激素.应用分子重组及PCR等技术,构建了一种鲑鱼生长激素基因分泌型表达质粒pOsGH153,使编码鲑鱼生长激素成熟肽的序列克隆在大肠杆菌分泌型表达载体PIN-Ⅲ-ompA内,直接位于编码大肠杆菌外膜蛋白A信号肽序列的下游,在Lpp-Lac杂合启动子控制下,经IPTG诱导,分子量约23 000的鲑鱼生长激素在大肠杆菌中获得高效表达,该产物具有天然鲑鱼生长激素的免疫活性,直接分泌到细胞周质,而信号肽被自动剪除.     

民勤红砂岗地区绵刺分布和繁殖方式及濒危原因调查

本文调查了民勤红砂岗地区绵刺的分布现状和面积,初步观测了它的生活习性和繁殖方式,发现枝条生根是它的重要繁殖方式,并对绵刺濒危的原因和保护措施进行了讨论。     

合理用药生态控制茶小绿叶蝉主要措施与评价

合理用药生态控制茶小绿叶蝉主要措施与评价张觉晚,王沅江（湖南省茶叶研究所,长沙４１０１４５）ＰｒｉｎｃｉｐａｌＴｅｃｈｎｉｑｕｅｓｏｆＲａｔｉｏｎａｌＵｓｅｏｆＰｅｓｔｉｃｉｄｅｆｏｒＥｃｏｌｏｇｉｃａｌＣｏｎｔｒｏｌｏｖｅｒＴｅａＧｒｅｓｎＬｅａｆ...     

短杆菌肽通道内离子K~＋，Na~＋，Li~＋与水的相关性

基于右手螺旋短杆菌肽Ａ离子通道模型,利用分子动力学计算机模拟方法研究了通道内离子Ｋ＋,Ｎａ＋,Ｌｉ＋与水分子的相关性．     

Sucrose Synthase,Starch Accumulation,and Tomato Fruit Sink Strength

Contrasting evidence has accumulated regarding the role of acid invertase and sucrose synthase in tomato fruit sink establishment and maintenance. In this work the relationships among the activities of sucrose synthase and acid invertase, Lycopersicon esculentum Mill cv UC-82B fruit growth, and starch accumulation were analyzed in fruit at 0 to 39 d after anthesis. Sucrose synthase, but not acid invertase, was found to be positively correlated with tomato fruit relative growth rate and with starch content in the pericarp tissue. A similar association between sucrose synthase activity and starch accumulation was also evident in the basal portion of the stem. Heat-shock treatments, which inhibited the increase in sucrose synthase activity at the beginning of the light period and had no effect on acid invertase activity, were used to examine the importance of sucrose synthase in relation to sucrose metabolism and starch synthesis. After the heat-shock treatment, concomitantly with the suppressed sucrose synthase activity relative to the controls, there was a reduction in sucrose cleavage and starch accumulation. These data substantiate the conclusion that, during the early phases of tomato fruit development, sucrose synthase rather than acid invertase is the dominant enzyme in metabolizing imported sucrose, which in turn plays a part in regulating the import of sucrose into the fruit.