Transmission electron microscopy and atomic force microscopy characterization of nickel deposition on bacterial cells

Recently bacterial cells have become attractive biological templates for the fabrication of metal nano- structures or nanomaterials due to their inherent small size, various standard geometrical shapes and abundant source. In this paper, nickel-coated bacterial cells (gram-negative bacteria of Escherichia coli) were fabricated via electroless chemical plating. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) characterization results reveal evident morphological difference between bacterial cells before and after deposition with nickel. The bare cells with smooth surface presented transverse outspreading effect at mica surface. Great changes took place in surface roughness for those bacterial cells after metallization. A large number of nickel nanoparticles were observed to be equably distributed at bacterial surface after activation and subsequent metallization. Furthermore, ultra thin section analytic results validated the presence and uniformity of thin nickel coating at bacte- rial surface after metallization.     

黑腹果蝇品系纯合体杂交后代翅型变异的遗传分析

目的探究实验室条件下果蝇杂交后代所表现出的基因连锁、互换与自由组合效应,计算白眼、卷刚毛、小翅基因座位间的距离,并探索可能的基因互作。方法将三隐性（白眼、卷刚毛、小翅）与残翅两种品系的果蝇进行杂交,并使F1代互交,对正反交的F2代进行表型数据统计分析。结果发现F2代出现新性状小皱翅,将其分为3种情况进行讨论,计算出了3个基因座位闻的距离。结论果蝇小翅和残翅基因互作产生了新性状小皱翅;在统计上它是一种“例外”新性状,而不是小翅或残翅范畴里的特情。     

黏性流中的链环涡管演化与螺旋度分析

本文通过直接数值模拟研究了链环涡管在不可压缩黏性流中的演化过程.在初始时刻的链环涡管由两个变形的涡环组合而成,其螺旋度为依赖于涡轴参数方程的解析表达式,进而可利用该初始流场进行涡管演化研究与螺旋度分析.发现当初始链环涡管的涡量方向具有相同手性时,链环涡管和环面纽结涡管的演化具有类似的涡动力学过程;而当它们具有相反手性时,涡管间的强涡量梯度会使两涡环在短时间内产生剧烈的涡重联,从而导致涡环由快速的尺度级串过程达到类湍流状态.     

QSAR analysis of substituted benzylamino- and heterocyclylmethylamino-carbodithioate derivatives of 4-（3H）-quinazolinone using CoMFA and SCORE2.0

Thymidylate synthase (TS) is a critical enzyme for DNA biosynthesis and many nonclassical lipophilic antifolates targeting this enzyme are quite efficient and encouraging as antitumor drugs. In this paper, the binding model of 14 antifolates of substituted benzylamino- and heterocyclylmethylamino- carbodithioate derivatives of 4-(3H)-quinazolinone with TS is examined using molecular simulation methods―― FlexiDock and SCORE2.0. The resulting conformation and orientation of these antifolates are directly applied to CoMFA study. The robust QSAR model, its three-dimensional contour map, and binding score of these antifolates derived from SCORE2.0 provide guidelines for structural optimiza- tion of current antifolates. The experiment indicates that deletion of cancer chemopreventive structure of dithiocarbamate is unfavorable for interaction between TS and antifolates.