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Biomedical subjects

C Nagata

Publications and source records attributed to C Nagata.

At least 127 records · Page 7Linked to original sources
PubMed1976

A molecular orbital study on the interaction between the cytochrome P-450 and its substrates.

Models for the interaction of the cytochrome P-450 with its substrates, namely for the type I interaction are proposed in which the molecular planes of the aromatic substrate and the porphyrins of P-450 are in parallel. Optical values such as transition energies and oscillator strengths for the isolated P-450 and P-450-substrate complex are calculated by means of molecular orbital method (ASMO SCF CI method), and they are compared with the observed values. The fact that no appreciable shift in the absorption peak of Soret band of P-450 was observed upon addition of substrate is reflected well in the calculation. Similarly, the well-known fact that the absorbance of the P-450 was decreased by mixing it with the substrate is also explained well by the calculated oscillator strength for the isolated P-450 and the stacked complexes. From the good agreement between the calculated results and the observed ones, it is suggested that the proposed models might be true reflections of the interactions between the P-450 and its substrates.

Binding Sites↗
PubMed1975

A fluorometric study of DNA-bound benzo[a]pyrene.

Comparisons were made among the fluorescence spectra of DNA-bound benzo[a]pyrenes which were produced in vivo and in vitro. DNA from mouse skin treated with benzo[a]pyrene had a maximum emission beyond 400 nm, which was clearly distinguished from that of DNA-bound benzo[a]pyrene 4,5-oxide. The emission spectra from mouse skin were classified into two groups, type I and type II. The former was similar to the spectrum of benzo[a]pyrene, although the two maxima were shifted to longer wavelengths (410 and 435 nm). Type II was characterized by a broad peak around 430 nm. Type I and type II were obtained from different fractions of hydroxylapatite chromatography, but type I was changed into type II during storage. This suggests that type II is a modified product of type I. The emission spectra of both groups also were detected in in vitro activating systems, including photoirradiation, iodine treatment, and hydrogen peroxide treatment. Treatment of Escherichia coli with benzo[a]pyrene during culture produced only fluorescence of type I. Although the relationship between types I and II remains to be established, both types of fluorescence evidently indicate that the conjugated ring structure of the parent compound, benzo[a]pyrene, is preserved intact in DNA-bound benzo[a]pyrene. Several lines of evidence suggest that the proximate (active) form is an unidentified hydroxylated product including an oxy radical, but a cation radical cannot be completely excluded.

Animals↗