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Biomedical subjects

N A Kravchenko

Publications and source records attributed to N A Kravchenko.

At least 37 records · Page 2Linked to original sources
PubMed1978

[Action of egg lysozyme on representatives of the family Micrococcaceae. Its action on Micrococcus].

The results of the study of the effect of various concentrations of egg lysozyme on M. luteus and M. varians using 2 methods, i.e. serial dilutions in agar and turbidimetric are presented. It was found that the MIC of lysozyme for M. luteus ranged within wide limits, from less than 0.0003 to 1 mg/ml. M. varians was stable to lysozyme. The MIC for all the strains was 8 mg/ml. The turbidimetric method provided determination of general regularities in changes of the optical density in all the strains of M. luteus under the effect of various concentrations of lysozyme. On the basis of these data it was possible to consider the method as the most deep means for determining the intraspecies similarities in the surface structures of Micrococcus as compared to the method of serial dilutions in agar. The dynamics of the changes in the optical density of the M. luteus suspension markedly differed from that of M. varians.

Animals↗
PubMed1978

[Preparation and characteristics of carboxymethylated lysozyme derivatives].

Hen egg-white lysozyme (EC 3.2.1.17) was carboxymethylated with iodoacetic acid and the individual products of various degree of modification were isolated by column chromatography on Amberlite CG-50. Peptide mapping of the products obtained reveals that His-15, Lys-1, -33, -96 (or -97) residues are blocked; the Lys-13 and -116 residues are unmodified. Salt activation of the carboxymethylated derivatives is facilitated with the increase of the number of modified groups; this fact is consistent with the increased lytic activity and affinity to substrate of the derivatives at lowered ionic strength.

Chromatography, Ion Exchange↗
PubMed1978

[Mobility on peptide maps of peptides obtained by tryptic hydrolysis of lysozyme oxidized at the S-S-bonds].

The peptide map obtained by tryptic hydrolysis of the lysozyme oxidized at the S--S-bonds was characterized and compared with that of tryptic hydrolysis of the reduced lysozyme. It was shown that the mobility of peptides containing oxidized amino acid residues is decreased under electrophoresis and chromatographic treatment. Under a decrease in the peptide charge during oxidation, the changes in electrophoretic and chromatographic mobilities show a correlation. In case when the peptide charge remains unchanged, only chromatographic mobility may be altered. It is demonstrated that the cystein residues significantly interfere with the effects of trypsin on the adjacent bonds.

Chromatography, Paper↗
PubMed1977

[Interrelationship between toxigenic and non-toxigenic diphtheria microbes in the epidemic process].

A study of the circulation of toxigenic and nontoxigenic diphtheria bacilli was carried out in several carrier state foci under conditions of a natural course of the epidemic process. There were 2623 persons under observation. A total of 32158 analyses were carried out, and 2271 strains were isolated and studied. No formation of the toxigenic variants of diphtheria bacillus as a result of phage conversion was revealed in the foci of carrier state despite the wide spread in them of nontoxigenic lysosensitive cultures capable of acquiring the toxigenic properties under experimental conditions, and of the cultures which had converting corinephages. Thus, autonomy of the circulation of the toxigenic and nontoxigenic diphtheria bacilli occurred in the carrier state foci; the leading role in the change of the diphtheria bacillus type belonged to reinfection.

Bacteriophage Typing↗
PubMed1977

[The role of the tryptophan-62 residue in the structure and function of lysozyme].

The thermostability and thermodinamics of formation of the enzyme-substrate complex of two oxidation products of chicken egg lysozyme with the tryptophane-62 residue modified to N'-formylkinurenine (with 2.5% activity) and kinurenine (with 27.5% activity) have been studied. In thermostability and pH effect on the substrate binding the lysozyme oxidation products do not differ from native lysozyme. The data obtained and thermodynamical characteristics of the enzyme-substrate complex formation suggest that the chemical nature of the 62 residue does not significantly affect the conformational properties of lysozyme, however, having a strongly pronounced effect on the binding of substrate and hence the total enzyme activity.

Chemical Phenomena↗
PubMed1977

[Isolation and some properties of mink lysozyme].

Lysozyme (EC 3.2.1.17) from spleen, kidney and liver of mink was isolated by affinity chromatography on deaminated chitin. The histidine content of mink lysozyme is unusually high and comprises 7 residues per mole of the protein. The acidic and basic amino acid residues are present in the mink lysozyme in nearly equal amounts (20-22); in this respect, the degree of amidation of the side chain carboxylic groups is relatively low (8-10). The lysozyme preparations obtained are found to contain an unknown, tightly bound component, absorbing at 400-420 nm.

Amino Acids↗
PubMed1976

[Discontinous nature of heat denaturation of lysozyme].

Optical density of lysozyme solutions at 290 nm on heating from 20 to 80 degrees C is shown to be changing in multistep way. Character of the changing depends on pH and ionic strength of medium. It is assumed that the results obtained reflect the multistep nature of lysozyme thermal denaturation.

Hot Temperature↗
PubMed1976

[Nature of tryptophan photooxidation products in lysozyme in the presence of methylene blue].

One out of six trytophan residues in two lysozyme modification, obtained under lysozyme photooxidation in the presence of methylene blue, is found to be oxidized to N'-formylkinurenine (in one modification) and to kinurenine (in the other modification). The transition of one modification into another via detaching of N'-formyl group by soft acid hydrolysis has shown that one and the same tryptophan residue is oxidized in both products, Possible mechanism of tryptophan oxidation to the products mentioned is discu-sed on the basis of the hypothesis on signlet mechanism of lysozyme photooxidation in the presence of methylene blue.

Chitin↗
PubMed1976

[Selectivity of lysozyme oxidation by singlet oxygen].

Peptide analysis of tryptic hydrolysates of two lysozyme forms derived from oxidation of lysozyme with singlet oxygen shows that Trp-62, located at the active site, is destroyed. This is confirmed by the protective effect of the substrate (chitin), whose presense practically prevents the oxidation. A possibility of oxidating different tryptophan residues is discussed from the view-point of their availability to the reagent.

Animals↗
PubMed1975

[Production of a lysozyme-like enzyme by various representatives of the genus Staphylococcus].

On the basis of studying 855 strains of various staphylococci it was shown that production of a lysozyme-like enzyme (LLE) failed to serve as a characteristic sign for all the representatives of Staphylococcus genus. It was mostly observed in S. aureus (in 85% of the strains). In nonpathogenic strains of S. epidermidis LLE could not be revealed either by the dish or by affine chromatography on chitin; among S. epidermidis, isolated from the patients there were cultures which did or did not form the LLE. Cultures occupying an intermediate position (coagulase-negative or mannite-negative) formed the LLE in 66.9% of cases. It was shown that the virulence and the general biological activity of the lysozyme-positive intermediate strains were higher than in the lysozyme-negative ones.

Animals↗
PubMed1975

[Antibacterial activity of a lysozyme-like enzyme from staphylococci].

A lysozyme-like enzyme isolated from the culture broth of Staph. aureus 712 presented in its native state a lipoproteid complex. The lytic and antibacterial spectrum of the enzyme was similar to that of the egg albumin enzyme. However, the lipoproteid complex was somewhat superior to the egg albumin complex in its activity against Micrococcus lysodeikticus, a number of gramnegative bacteria and staphylococci. Out of the organisms studied Microccus lysodeikticus, Sarcina and Bac. subtilis proved to be most sensitive to the both enzymes. Comparison of the amount of the enzyme formed in the culture medium with its minimum inhibitory concentration with respect to most of the microbes tested provided a supposition that the lipoproteid enzyme did not play a significant role in the process of the microbial antagonism.

Acetylglucosaminidase↗