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Biomedical subjects

B Lubas

Publications and source records attributed to B Lubas.

At least 19 recordsLinked to original sources
PubMed1986

Interaction of haemoglobin and cytochrome c with aliphatic alcohols as studied by 1H NMR spectroscopy.

Association of haeme proteins, haemoglobin and cytochrome c, with eight aliphatic alcohols (methanol, ethanol. two isomeric propanols and four butanols) was studied by 1H NMR spectroscopy. NMR spectra of alcohols were monitored at 60 MHz at increasing concentration of the proteins. Selective broadening of the NMR signals of individual segments of alcohols was observed only in the case of alcohol-haemoglobin systems. Its quantitative evaluation and interpretation in terms of formation of low affinity intermolecular alcohol--protein complexes led to the conclusion that haemoglobin associates with alcohol molecules in a way depending on the length and isomeric branching of the alkyl chains; in particular, the methylene and methine groups vicinal to the hydroxyl are subject to stronger immobilization than the terminal methyls or other groups. Thus, the model of hydrophobic complexes stabilized by hydrogen bonds described previously for association of bovine serum albumin with alcohols (Lubas et al., Biochemistry, 18, 4943-4951, 1979) seems to apply also to haemoglobin association. In the case of cytochrome c association, 1H NMR data alone are insufficient for structural evaluation of the mechanism of formation of the alcohol--cytochrome c complexes.

Alcohols↗
PubMed1984

Association of the radiosensitizers metronidazole and misonidazole (RO-07-0582) with bovine serum albumin. Effect of urea and ionic strength.

The stability of association of nitroimidazole radiosensitizers (metronidazole and misonidazole) with bovine serum albumin (BSA) was examined in aqueous solutions by 1H n.m.r. spectroscopy in the presence of urea (0-8M) as denaturant, or high salt concentration (NaCl0-5M). A broadening of n.m.r. lines of the two radiosensitizers observed in the presence of BSA disappeared with increasing urea concentration. An especially large narrowing effect was observed for the lines attributed to the methylene group near to the hydroxyl in the side chain of misonidazole. The results suggest a release of both radiosensitizers from their binding sites on unfolding by urea of the polypeptide chain of BSA. The increase of ionic strength I caused a monotonic enhancement of broadening by BSA of the metronidazole lines. For misonidazole, the enhancement of broadening was observed at values of I greater than 1, but at low (less than 1 M) concentrations of NaCl the broadening disappeared. Thus, the results obtained in the systems with salt reflect quantitative changes in hydrophobic and hydrogen-bonded contributions to binding of aliphatic moieties of radiosensitizers to BSA.

Magnetic Resonance Spectroscopy↗
PubMed1983

1H and 13C NMR characteristics of the anticancerous derivative of acridine: Ledakrin C-283 (nitracrine).

For the anticancerous derivative of acridine--Ledakrin C-283 [1-nitro-9-(3-dimethylaminopropylamino)-acridine . 2HCl-H2O] 1H and 13C NMR spectra were assigned and analysed with particular emphasis on pH effects. On pH increase in 2H2O, the deprotonation of N(10) in Ledakrin aromatic core causes a high and selective upfield shift of the resonances for aromatic protons and strong deshielding for aromatic carbons C(11)-C(14), especially those adjacent to N(10). The signals of remaining aromatic carbons are shifted upfield on increase of pH, whereas those of protons and carbons in aminoaliphatic chain at C(9) are only slightly affected by change of pH. The above NMR characteristics of Ledakrin may be useful in studies on mechanisms of its interaction with proteins and nucleic acids in aqueous solution at various pH values.

Aminoacridines↗
PubMed1979

The effect of pH on colchicine conformation and structure.

The effect of various pH values between 0 and 14 on the structure and conformation of colchicine was examined using UV-vis spectrophotometry at a concentration of 1.7 x 10(-5) M and NMR techniques at a colchicine concentration of 0.1M. The complete interpretation of the colchicine NMR spectrum in D2O is given. A stable structure of the colchicine molecule in aqueous solutions at pH from 2 to 12 was demonstrated. However, during incubation at 40 degrees C colchicine was found to be stable only at pH values between 2 and 10. The significance of these data for reactions of cholchicine in regard to metabolism and interaction with macromolecules is discussed.

Colchicine↗