Chemical composition of a preparation of the cell walls of Corynebacterium diphtheriae

The chemical characteristics of 6 batches of the preparation, obtained from the cell wall of C. diphtheriae grown in liquid and solid culture media, with respect to their content of nitrogen, hexoses, pentoses, total amino sugars, lipids and to the possible admixture of nucleic acids are presented. From the results of the chemical analysis of these batches their standardization according to the ratio of total amino sugars and pentoses to total nitrogen in C. diphtheriae cell-wall preparation is proposed.     

蚕豆叶片发育与衰老过程中超氧物歧化酶活性与丙二醛含量变化

蚕豆植株叶片随茎节自上而下表现出明显的发育与衰老顺序,可作为衰老特征的是叶绿素和蛋白质含量明显下降。蚕豆叶中SOD活性主要定位于12 000× g离心后所得的上清液和叶绿体组分。衰老叶片的SOD总活性和叶绿体组分的相对活性都有所下降,SOD同工酶谱也发生了改变。O_2~ 产生速率随叶龄增大而稍上升;而MDA含量在叶片外观表现枯黄衰老征兆前就急剧上升。可能因为衰老叶片过氧化氢酶活性大幅度下降与SOD之间的不平衡,致使O_2~ 代谢中间产物累积而引起膜的损伤.     

Genetic analysis of the yeastCandida maltosa by means of induced parasexual processes

The usefulness of hybridization by protoplast fusion and mitotic segregation for the genetic analysis of the imperfect fodder yeastCandida maltosa was tested. Mitotically stable fusion hybrids were obtained with frequencies between 10^–6 and 10^–7. Complementation tests were performed by protoplast fusion. Substances that are known to induce frequent mitotic segregation in other yeast species such as benomyl, p-fluorophenylalanine, and acriflavine were ineffective inC. maltosa. UV irradiation induced mitotic segregation in up to 10%. This agent induced mainly mitotic crossing over inC. maltosa. Our data enabled the construction of the linkage group I with the sequenceCEN-ade-26-pro-1.     

Biosynthesis of lysosomal hydrolases: their synthesis in bound polysomes and the role of co- and post-translational processing in determining their subcellular distribution

By in vitro translation of mRNA’s isolated from free and membrane-bound polysomes, direct evidence was obtained for the synthesis of two lysosomal hydrolases, β-glucuronidase of the rat preputial gland and cathespin D of mouse spleen, on polysomes bound to rough endoplasmic reticulum (ER) membranes. When the mRNA’s for these two proteins were translated in the presence of microsomal membranes, the in vitro synthesized polypeptides were cotranslationally glycosylated and transferred into the microsomal lumen. Polypeptides synthesized in the absence of microsomal membranes were approximately 2,000 daltons larger than the respective unglycosylated microsomal polypeptides found after short times of labeling in cultured rat liver cells treated with tunicamycin. This strongly suggests that nascent chains of the lysosomal enzymes bear transient amino terminal signals which determine synthesis on bound polysomes and are removed during the cotranslational insertion of the polypeptides into the ER membranes. In the line of cultured rat liver cells used for this work, newly synthesized lysosomal hydrolases showed a dual destination; approximately 60 percent of the microsomal polypeptides detected after short times of labeling were subsequently processed proteolytically to lower molecular weight forms characteristic of the mature enzymes. The remainder was secreted from the cells without further proteolytic processing. As previously observed by other investigations in cultured fibroblasts (A. Gonzalez-Noriega, J.H. Grubbs, V. Talkad, and W.S. Sly, 1980, J Cell Biol. 85: 839-852; A. Hasilik and E.F. Neufeld, 1980, J. Biol. Chem., 255:4937-4945.) the lysosomotropic amine chloroquine prevented the proteolytic maturation of newly synthesized hydrolases and enhanced their section. In addition, unglycosylated hydrolases synthesized in cells treated with tunicamycin were exclusively exported from the cells without undergoing proteolytic processing. These results support the notions that modified sugar residues serve as sorting out signals which address the hydrolases to their lysosomal destination and that final proteolytic cleavage of hydrolase precursors take place within lysosome itself. Structural differences in the carbohydrate chains of intracellular and secreted precursors of cathespin D were detected from their differential sensitivity to digestion with endoglycosidases H and D. These observations suggest that the hydrolases exported into the medium follow the normal secretory route and that some of their oligosaccharides are subject to modifications known to affect many secretory glycoproteins during their passage through the Golgi apparatus.     

The Search for Agroislands in the Chickpea Genome

Biophysics - The concentration of genes that control domestication traits in so-called “agroislands” complicates breeding. Therefore, information about where such islands are located in...     

Genetic Identification of Soybean Varieties Using Single-Nucleotide Polymorphisms

Biophysics - Abstract—A method for certification of soybean varieties was developed based on single-nucleotide polymorphisms. A genetic algorithm was used to select an optimal set consisting...