Biomedical subjects

M I Mendzhul

Publications and source records attributed to M I Mendzhul.

At least 37 records · Page 2Linked to original sources

PubMedDate not supplied

[Comparative characteristics of physico-chemical and regulating properties of aspartate kinases from three species of cyanobacteria].

Aspartokinases have been isolated from the cell-free extracts of Plectonema boryanum, Anabaena variabilis and Synechococcus cedrorum. Their physico-chemical characteristics and peculiarities of retroregulation by amino acids were studied. It has been shown that in P. boryanum cells aspartokinase reaction is catalyzed by only one enzyme, which is similar to the previously described bacterial origin enzymes. Three izoenzymes, which differ in their main properties and amino acids-effectors, have been founded in the cells of A. variabilis. One enzyme with aspartokinase activity, which differs from other cyanobacteria enzymes in some physico-chemical features has been founded in the cells of S. cedrorum.

Aspartate Kinase↗

PubMedDate not supplied

[Localization of DNAase activity in cyanobacterium Plectonema boryanum CALU 465].

It was shown in experiments carried out on cyanobacterium P. boryanum, that when cells are incubated in a buffer with low concentrations of nonion detergent (0.1%, Triton X-100) one can observe the DNAse activity release into the medium. The methods of supersound desintegration of cells and following gradient centrifugation of the cell-free extracts were used to obtain three fractions of the cell membranes identified by means of spectrophotometric analysis. It has been established that P. boryanum is characterised by high level of DNAse activity associated with the cytoplasmic cell membrane. As to its activity character the DNAse under study belongs to the class of nonspecific endonucleases.

Cell Membrane↗

PubMedDate not supplied

[Isolation and purification of nonspecific nuclease of cyanobacterium Plectonema boryanum CALU 465].

Nonspecific nuclease has been isolated from the cells of cyanobacterium Plectonema boryanum and purified to homogenic state. It has been established that the method of centrifugation of cell-free culture extract in the sucrose density gradient is efficient for the separation of pigment proteins and enzyme concentration. Under the successive use of two ion-exchangers the nuclease activity was determined in the concentration range of NaCl 0.065-0.085 M after separation of the cell-free cyanobacterium extract on the column with phosphocellulose in the range of 0.2-0.25 M, on the column with DEAE--Toyopearl respectively. The molecular mass of nuclease which is 40 kDa, has been determined by electrophoresis in polyacrylamide gel under denaturating conditions and gel-filtration on Sephadex G-100. It has been also established that the given enzyme is monosubunitary as to its structure.

Cellulose↗

PubMedDate not supplied

[Phagoresistance of filamentous cyanobacteria clones].

The paper deals with formation regularities of phagoresistant clones of cyanobacteria in two productive virus-cell systems: heterocyst cyanobacterium Nostoc linckia--cyanophage N-2, and mutant in heterocysts strain of Anabaena variabilis--cyanophage A-1. Frequency of spontaneous formation of phagoresistant clones of cyanobacterium N. linckia varies within 1.0-8.0 x 10(-6) per a cell, A. variabilis--5.0 x 10(-6)-7.0 x 10(-7) per cell. All the studied phagoresistant clones of N. linckia have identical morpho-cultural properties and do not differ from those of the initial culture. Phagoresistant clones of A. variabilis are presented by two groups. One of them, as to its properties, does not practically differ from the wild type culture. The second group differs considerably from the initial culture A. variabilis as to a number of characteristics--time of colonies appearance, their amount, length of trichomas, specific rate of growth and biomass accumulation. Spontaneous transfer of cyanophages to the culture liquid of clones resistant forms of cyanobacteria has not been revealed. Lysis of cells of the studied clones also was not induced under the effect of mytomycin C, thermal treatment and UV-irradiation. Cyanophage N-2 is not adsorbed by the cells of resistant cloned forms of cyanobacteria N. linckia. Only nonspecific adsorption takes place on the cells of phage-resistant clones of A. variabilis of both groups: about 20% of virions introduced in the adsorption mixture. Basing on the data obtained, it is supposed that phage-resistance of stable clones of filamentous cyanobacteria under the conditions of the given experiment is determined by the structure modification of cells receptors.

Anabaena↗

PubMedDate not supplied

[pSTS4--a new shuttle vector for cyanobacterium Plectonema boryanum CALU 465].

Three vector constructions--pSTS2, pSTS3 and pSTS4 have been obtained on the basis of the standard vector for Escherichia coli pBR 322, cyanobacterial plasmid pSM1 and its separate fragments. The structure of pSTS4, carrying the full-size plasmid pSM1 (cloned by the restriction site Hpa II), replicated both in the cells of E. coli and in the cells-transconjugants of the trichomal cyanobacterium Plectonema boryanum. Under these conditions resistance of P. boryanum cells to ampicillin increases three orders, and to tetracyclin--50 times. Structural integrity of pSTS4 is stably supported in conjugates during seven successive passages (time of the experiment) and preserved the transforming capacity in respect of the cells of E. coli. It is supposed that pSTS4 is a shuttle-vector with two active origins of replication; one of them provides for the replication of pSTS4 in E. coli cells, another--in P. boryanum cells.

Ampicillin↗

PubMedDate not supplied

[2 site-specific endonucleases of the cyanobacterium Nostoc linckia].

Two restrictases Nli387/7 I and Nli387/7 II have been isolated from cyanobacterium Nostoc linckia using chromatography on phosphocellulose, "Mono Q" column, and heparin sepharose 4B. The preparations are described by the method of electrophoresis in polyacrylamide gel under denaturing conditions. Catalytic properties of restrictases are determined: optimal pH of the action--9.0--9.5, optimal concentration of Na+--5 mM, that of Mg2+--6 mM, optimal temperature--37 degrees C. The isolated enzymes are isoschizomers of restrictases avaI and AvaII. The point of cutting is determined for enzyme Nli387/7 I. It is shown that restrictase Nli387/7 I is a false isoschizomer Ava I.

Binding Sites↗

PubMedDate not supplied