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Biomedical subjects

E Borowski

Publications and source records attributed to E Borowski.

At least 73 records · Page 4Linked to original sources
PubMed1990

Influence of net charge on the aggregation and solubility behaviour of amphotericin B and its derivatives in aqueous media.

The poor solubility of polyene antibiotics in aqueous media limits their application in the therapy of systemic fungal infections. In the present paper we have demonstrated that the ionic state (net electrical charge) of the antibiotic molecule is an important factor in determining the aggregation and solubility properties of amphotericin B and its derivatives. A multi-step model of polyene self-association in aqueous media has been proposed as an explanation for the fact that some major differences are observed when aggregation is monitored by different techniques.

Amphotericin B↗
PubMed1990

Anticandidal properties of N3-(4-methoxyfumaroyl)-L-2,3-diaminopropanoic acid oligopeptides.

Tri-, tetra-, and pentapeptides containing N3-(4-methoxyfumaroyl)-L-2,3-diaminopropanoic acid (FMDP), an inactivator of glucosamine 6-phosphate synthase of fungal origin (a key enzyme in the biosynthesis of macromolecular components of the fungal cell wall) have been synthesized and investigated as anticandidal agents. Structure-activity relationships of a series of peptides revealed that tripeptides were generally more active than the other peptides examined. In this study, the lysyl peptide, Lys-Nva-FMDP has been found to be the most active compound in the series.

Alanine↗
PubMed1990

Antimicrobial properties of N3-(iodoacetyl)-L-2,3-diaminopropanoic acid-peptide conjugates.

Six peptide conjugates consisting of either norvaline, methionine, or lysine and N3-(iodoacetyl)-L-2,3-diaminopropanoic acid--a strong, irreversible inactivator of bacterial and fungal glucosamine-6-phosphate synthase--were synthesized and their antibacterial and antifungal activities were evaluated. Antimicrobial potencies of these peptides were correlated with their transport and cleavage rates inside the cells. Bacteriolysis of Bacillus pumilus cells and inhibition of [14C]glucose incorporation into cell-wall polysaccharides of Candida albicans as a result of glucosamine 6-phosphate inactivation were also observed. Reversal of growth inhibitory effect of these peptides by N-acetylglucosamine in bacteria and fungi suggests the effective delivery of N3-iodoacetyl-L-2,3-diaminopropanoic acid into the cell by a peptide-transport system.

Anti-Bacterial Agents↗
PubMed1990

Low stimulation of NADH oxidation and oxygen consumption by 5-iminodaunorubicin and its derivatives.

NADH oxidation and oxygen consumption mediated by 5-iminodaunorubicin and its derivatives have been studied. Experiments were carried out using two enzyme system: microsomes isolated from rat liver and cytochrome c-reductase. All 5-iminoanthracyclines examined were relatively poor electron transfer mediators. In addition, 5-imino-derivatives of daunorubicin modified at sugar moiety were less effective in stimulating NADH oxidation and oxygen radical production than 5-iminodaunorubicin itself. This may be due to the additive effect of 5-imino structure and the presence of bulky substituents at sugar moiety, which might make the compounds poor enzyme substrates.

Animals↗
PubMed1989

Lack of competition between cytochrome c and anthraquinone type drugs for the reductive sites of NADH dehydrogenase.

We have shown that (i) the cytochrome c reductase activity of the commercial NADH dehydrogenase does not perturb its ability to catalyse the reduction of various antitumor compounds of the anthracycline class, (ii) the reduction of these compounds by NADH, catalysed by commercial NADH dehydrogenase, correlates with their reduction by NADH catalysed by microsomes. Moreover, our data strongly suggest that two catalytic sites are present, one for cytochrome c and one for quinone type compounds.

Animals↗
PubMed1989

Relationship between ionophoric and haemolytic activities of perimycin A and vacidin A, two polyene macrolide antifungal antibiotics.

The ionophoric and hemolytic activities of two antifungal aromatic heptaenes: vacidin A and perimycin A, were studied on human red blood cells. Measurements of hemolysis, K+ influx and efflux, H+ movement and potential difference across the cell membrane, show that the hemolytic activity, being related to the K+ permeability induced by the polyene, is strongly dependent on the ability of this polyene to induce H+ movement. It was shown that: (1) both antibiotics have approximately the same efficiency in inducing K+ permeability, but a 100-fold difference in their hemolytic activity; (2) their hemolytic activity is related to their ability to induce H+ movement; (3) the protonophoric activity requires the existence of a free carboxyl group in the macrolide ring, as in vacidin A. The hemolytic activity is determined by the intrinsic efficiency of a K+/H+ exchange induced by this polyene. With perimycin A, which lacks the free carboxyl group, the hemolytic activity is dependent on the Cl- conductive flux which slows down the K+ flux.

Acetophenones↗
PubMed1989

Comparative conformational analysis of cholesterol and ergosterol by molecular mechanics.

A comparative conformational analysis of cholesterol and ergosterol has been carried out using molecular mechanics methods. These studies are aimed at giving a better understanding of the molecular nature of the interaction of these sterols with polyene macrolide antibiotics. Structures of cholesterol and ergosterol determined by X-ray methods have been used as initial geometries of these molecules for force field calculations. The calculation of steric energy has also been made for conformations which do not appear in the crystal. The latter conformers have different conformations of the side chain as well as different conformations of rings A and D. The rotational barriers around bonds C17-C20 and C20-C22 have also been calculated. The results obtained on differences and similarities in the conformations of cholesterol and ergosterol allow us to postulate a mechanism for differential interaction with the antibiotics. The relatively rigid side chain of ergosterol (stretched molecule) in comparison with the flexible side chain of cholesterol (bent molecule), allows better intermolecular contact of the first sterol molecule with a polyene macrolide and in consequence facilitates complex formation involving Van der Waal's forces.

Calorimetry↗
PubMed1989

The structure of vacidin A, an aromatic heptaene macrolide antibiotic. I. Complete assignment of the 1H NMR spectrum and geometry of the polyene chromophore.

The constitution of vacidin A, a representative of the aromatic heptaene macrolide antibiotics was established on the basis of 13C and 1H-1H double quantum filtered correlated spectroscopy, rotating frame nuclear Overhauser effect spectroscopy, J-resolved 1H as well as 1H-13C correlation NMR spectra. Geometry of the polyene chromophore was determined as 22E,24E,26E,28Z,30Z,32E,34E.

Anti-Bacterial Agents↗
PubMed1989

The structure of vacidin A, an aromatic heptaene macrolide antibiotic. II. Stereochemistry of the antibiotic.

On the basis of coupling constants and rotating frame nuclear Overhauser effect spectroscopy of vacidin A methoxycarbonylmethylamide, the stereochemistry of the antibiotic was established. The configuration of the aglycone was determined as (3R,7R,9R,11S,13S,15R,17S,18R,19S,21R, 36S,37R,38S). The aminosugar constituent of the antibiotic was identified as beta-(D)-mycosamine. The chiral center at C-41 remains to be assigned.

Anti-Bacterial Agents↗
PubMed1988

Quantitative structure-activity relationships in amphotericin B derivatives.

The quantitative structure-activity relationships studies of amphotericin B and its 16 semisynthetic derivatives obtained by modification at carboxyl and amino groups have been done. The results of five biological tests were subjected to principal component analysis, a numerical method useful in the investigation of large sets of data. For some compounds, also, interaction with lipidic vesicles was investigated by spectroscopic methods. The results obtained indicate that: (i) The presence of positively charged nitrogen atom (protonable or bearing fixed charge) is indispensable for biological activity and antibiotic-sterol interaction; (ii) The lack of free carboxyl group in the molecule favours the differentiation between cholesterol and ergosterol containing cells.

Amphotericin B↗
PubMed1988

Interaction of 14C-labelled amphotericin B derivatives with human erythrocytes: relationship between binding and induced K+ leak.

Four 14C-labelled amphotericin B (Am B) derivatives with different net electric charges were examined: zwitterionic N-fructosyl Am B, positively charged N-fructosyl Am B methyl ester, negatively charged N-acetyl Am B and neutral N-acetyl Am B methyl ester. The binding of these four derivatives to human red cells and their octanol-water partition coefficients were measured. Simple partitioning between red cells and buffer was found for the four compounds, regardless of concentration, within a range of 10(-8) and 10(-4) M. This indicates the absence of cooperativity and saturability of binding at least in this concentration range. The constant partition coefficients were found to be three to five times higher for the two methyl ester derivatives than for the two non-esterified compounds. All partition coefficients were proportional to those found for the octanol-water system. Efficiency in inducing K+ leak from red cells was measured during the binding experiments. Despite the higher partition coefficients of the two methyl ester derivatives, they were found to have much lower ionophoric efficiency than the two non-esterified compounds. These results are discussed in terms of the mechanism of permeability pathway formation by polyene antibiotics.

Amphotericin B↗
PubMed1988

Synthesis and antineoplastic evaluation of 1,4-bis(aminoalkanamido)-9,10-anthracenediones.

The effect of the replacement of amino groups, attached to the anthraquinone ring in [(aminoalkyl)amino]-anthraquinones, by an amido function on DNA binding, cytotoxicity, and antileukemic activity has been studied. The corresponding 1,4-bis(aminoalkanamido)-9,10-anthracenediones have been synthesized and examined. It has been concluded that such modification does not exclude the DNA binding and cytotoxicity of mentioned compounds but decreases or abolishes the in vivo antileukemic activity.

Animals↗