Analysis of the energies of the triple base triplets

Sixty-four sets of three-dimensional models of DNA triplex base triplets (TBT) were built up based on codons by homologous modeling method and their energies were minimized. According to sequence of TBT and orientation of the third ODN strand third, the energies of monomers and water-K+-TBT ternary complexes of TBT were analyzed. The results showed: (i) The energies of the symmetric parallel monomers are generally lower than those of the symmetric anti-parallel monomers of TBT, but the energies of the symmetric parallel ternary complexes are higher than those of the symmetric anti-parallel ternary complexes of TBT. (ii) No matter TBTs are monomers or ternary complexes, the energies of asymmetric parallel TBTs are generally lower than those of the asymmetric anti-parallel ones. (iii) Although the energies of the parallel TBTs are correlated with those of the anti-parallel ones, the energy differences are significant between them. The results here suggest the sequences of TBTs and the orientations of the third ODN strands are two of the key factors that can influence the formation and stability of TBT. (C) 2002 Elsevier Science B.V. All rights reserved.

鲤鱼多态性EST标记的筛选与特性分析

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湖北钉螺在不同温度下的发育速率及形态变化

从野外采回的钉螺在室内各实验温度条件下均能正常产卵,其产卵量的高低与室温无关;在15-30℃的温度范围内,随着温度的升高钉螺的孵化期逐渐缩短;利用有效积温公式得知钉螺卵孵化的有效积温为193.55日度,发育起点温度为10.86℃;在各温度下初孵幼螺随着生长发育,螺壳的长宽比也随之加大.

香溪河流域水体环境因子研究

基于香溪河及其三大支流古夫河、高岚河与九冲河的8年监测数据,对该流域水体的环境因子及其时空动态进行了比较分析。结果显示,香溪河流域的水体呈中性偏弱碱性,属于中等硬度水,水体溶解氧丰富,还原性物质以及氯化物水平不高,具有较强的缓冲能力。多数环境因子具有明显的季节变化,而年际变化规律不显著。香溪河流域水体的主要营养元素氮含量较高,并以有城镇影响的古夫河为最;高岚河由于受到生活污水与农业活动的影响,水质相对较差;香溪河的磷污染严重;森林覆盖率较高的九冲河的水质最佳。在香溪河流域,氮主要以面源污染的方式进入河道,

丙体六六六对斜生栅藻生长及光合色素和膜脂过氧化影响的研究

采用室内培养试验方法,研究了丙体六六六(γ-HCH)对斜生栅藻生长和生理生化的影响。结果表明,在γ-HCH浓度<0.2mg·L-1时对斜生栅藻生长有促进作用,在2mg·L-1时则表现为抑制作用,其对叶绿素的影响与对藻密度的影响一致,显示浓度-效应关系。γ-HCH对斜生栅藻的超氧化物歧化酶(SOD)的影响表现为,在0.02mg·L-1时达到峰值,然后下降,在2mg·L-1时其活性只有对照的38.18%。γ-HCH对斜生栅藻的膜脂过氧化的影响,在<0.02mg·L-1时变化不大,而在0.2mg·L-1和2mg

人工湿地中试系统基质中藻类组成的研究

从2003年3月到2004年2月,在水力负荷为600mm/d的条件下研究了人工湿地中试系统(mediumscaleplot,MSP)基质中藻类的组成.结果表明,栅藻、小球藻、盘星藻、空星藻、纤维藻、舟行藻、小环藻、平裂藻和颤藻属的一些种类在下行池基质各层不同季节均有出现,下行池表层藻类较丰;上行池基质中不同季节的藻类组成中念珠藻和鱼腥藻均为固氮种类,菱板藻、舟行藻和卵形藻属的一些种类在上行池表层出现较多,上行池藻类组成较下行池少.本实验探讨了在人工湿地基质中存在的藻类组成,为湿地除藻机理和评估系统的稳定性