Characteristic features of the structure of co-integrating plasmids and simple insertions formed during transposition of the IS1 element in transposon Tn9'

Earlier we have studied unstable dissociating IS1/Tn9'-mediated cointegrates between the plasmids pDK57 (pBR322::Tn9') and pRP3.1, a deletion derivative of RP1, and two types of such cointegrates containing three and four copies of IS1 were revealed. In the present paper we studied the structure of stable IS1/Tn9'-mediates cointegrates and simple insertions formed by interaction between the plasmids pDK57 and pRP3.1 in the E. coli recA- cells. It was shown, that the stable cointegrates were formed by insertion of pDK57 in different loci of pRP3.1 and these cointegrates contain three copies of IS1, i.e. one copy of IS1 and a copy of Tn9' at the junction of the two replicons. The cointegrates are formed predominantly due to the activity of the left copy of Tn9', which occupies a proximal position in regard to the promoter of the cat gene. It was found that the integration of pDK57 into the kan gene region of pRP3.1 leading to the formation of the KmS cointegrates occurs only in one of the two possible orientations. Meanwhile the insertions of the transposon Tn9' into the kan region of pRP3.1 leading to simple insertions occurs in the orientation opposite to the orientation of the transposon in the KmS cointegrates. It is proposed that simple insertions are not the products of direct transposition of Tn9', but they are formed from unstable cointegrates under the action of IS1-specific resolvase.     

Interaction between D-glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase labeled by fluorescein-5'-isothiocyanate: evidence that the dye participates in the interaction

An interaction of rabbit muscle D-glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase labeled with FITC was studied by following the changes in fluorescence intensity of the bound dye. The association between the two enzymes was found to be a rather slow process characterized by a second order rate constant of 1.1 +/- 0.2.10(3) M-1 s-1, the KD of the complex between apoenzymes being 3.2.10(-7) M. The stability of the complex increased upon increase of temperature and ionic strength of the medium, suggesting a hydrophobic character of association. The ligands which bind at the active centers of the two enzymes (NAD+, ATP, 3-phosphoglycerate) weakened the bienzyme association. Unlabeled 3-phosphoglycerate kinase was unable to displace the FITC-labeled enzyme from the complex. Taken together, the results indicate that interaction between D-glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase labeled by FITC is assisted by the dye, which may bind at nucleotide-binding sites of GPDH. No interaction was observed between the FITC-labeled 3-phosphoglycerate kinase and lactate dehydrogenase, which suggests that protein-protein interaction at specific "recognition" sites may be a prerequisite for the complex formation.     

Function of crossing-over

The literature data are considered concerning the significance of genetic recombination and crossing over. An obvious result of recombination is production of the genotypically diverse offspring, but the main role of recombination consists of combining the genes from diverging subspecies and races, thus maintaining a rather wide ecological potential of a species. This effect of recombination substantiates the tendency for increasing complexity of organic forms in progressive evolution. Accordingly, evolution is considered as a chain of recombinational "syntheses". The literature data treating crossing over as a mechanism of DNA repair are discussed. This function of crossing over is interpreted, based on a notion implying, from the composition of genetic code, that a crystalline associate composed of bases as free molecules precedes the appearance of DNA in evolution. The stability of the crystalline associate of bases was due to "balanced" distribution of bases for their electrochemical properties. The degeneracy of genetic code seems to provide possibility of construction of the electrostatically "balanced" base sequences in highly expressed bacterial genes. Crossing over possibly recovers "balanced" distribution of bases for their electrochemical properties and thus "repairs" a high level of heterocatalytic DNA activity.     

The genetic code as a clue to understanding of molecular evolution

The genetic code is comprised of a system concerning the distribution of doublets of the first two codon bases among amino acids. According to this system a definite order in the relative distribution of the first and the second codon bases coincides with a definite order among the common amino acids and their distribution for the number of hydrogen atoms per molecule (an unexpected parameter). The pattern of the relative distribution of the first and the second codon bases suggests it originated from a crystalline-like structure in which the set of bases AUGC served as an elementary structural unit and the base doublets played the role of structural analogs to the amino acids. These hypothetical crystalline-like aggregates are composed of the free molecules of amino acids and bases, and although different in their composition, should have an even number of hydrogen atoms per standard structural module.     

我国微茎类吸虫研究:ⅩⅢ.微茎类吸虫成虫结构特征排序

对我国52种微茎类吸虫的18项成虫形态学特征进行主成分分析,结果表明:卵巢位置、子宫延伸位置等7项性状对第一主成分贡献较大,提示描述器官位置的指标是重要的分类依据。52个虫种在前三个主成分上的排序图显示应将其划分成4个亚科。     

柱萤叶甲属研究（Ⅰ）鞘翅具黑色刻点的种类记述（鞘翅目：叶甲科）

本文就萤叶甲亚科中柱萤叶甲属鞘翅具黑色刻点的种类进行研究,共记述４种,我国已记录３种,其中１种为新种。     

我国微茎类吸虫的研究Ⅻ.类茎属及多黄属二新种报道：复殖目：微茎科

本文报道在湛江市附近海域海鸟体内获得的两种吸虫,经鉴定为新种,命名为巨口类茎吸虫,新种Ｍｉｃｒｏｐｈａｌｌｏｉｄｅｓ ｍａｃｒｏｓｔｏｎｒｓ ｓｐ．ｎｏｖ．,珊瑚多黄吸虫,新种Ｍｕｌｔｉｖｉｔｅｌｌｕｓ ｃｏｒａｌｉｕｓ ｓｐ．ｎｏｖ．     

以化学纯饲料饲养北京的桃蚜

应用修改后的Dadd和Mitter(1966)全纯饲料配方配制成人工饲料饲养定居在北京温室烟草上的桃蚜 Myzus persicae可完成生活史井连续饲养3代。本文描述饲料配制、饲养和取食量测定的方法。这3代初羽化无翅孤雌胎生雌蚜的平均体重分别为:440±90.7μg,264±104.9μg和312±127.9μg。用放射性同位素稀释法测定取食量的结果得悉若虫期的总取食量每蚜约为1.74μg,相当于1.16μl。     

Transposition of the deo operon structural genes in Escherichia coli K-12 to plasmid RP4 using bacteriophage mu]

Transposition of the structural genes of the deo operon of Escherichia coli K-12 into plasmid RP4 by means of temperate bacteriophage Mu was carried out. Some variants of composite RP4-deo-Mu plasmids were obtained and the expression of the deo genes integrated into the RP4 plasmid genome was studied. It was shown that the expression of these genes remains under the control of the chromosomal regulatory genes (deoR and cytR); although the activity of thymidine phosphorilase in the strain E. coli which contains hybrid plasmid is 4-6 fold greater than that in strains of E. coli with chromosomal localization of the deo operon.