Yasushi Kodera

Dinitrofluoranthene: induction, identification and gene mutation

By renitrating 3-nitrofluoranthene in the presence of fuming nitric acid, some additional nitro-derivatives were induced; they were identified as 3,7-, 3,9- and 3,4-dinitrofluoranthene (DNF), and two trinitrofluoranthenes (TNF, 3,4,7- and 3,4,8- or 3,4,9-isomers) on the basis of the results of mass spectrometry and 1H-nuclear magnetic resonance. The yield of 3,7- and 3,9-DNF was about 61.3% in all of the derivatives induced. All of the DNFs yielded positive results in the rec-assay system, inducing DNA-damaging activity in Bacillus subtilis. Both 3,7- and 3,9-DNF converted Salmonella typhimurium His- strains TA98, TA97 and TA1538 from autotrophy to prototrophy, indicating a frameshift-type mutation for both; for strain TA98, 3,7-, 3,9- and 3,4-DNF gave mutagenicity of 422, 355 and 15.5 His+ revertants, respectively, per nanogram, corresponding to the specific activity of 1,6-dinitropyrene (DNP), a powerful mutagen. These DNFs are known to be potential mutagens which are eluted at adjacent retention times with 1,3-, 1,6- and 1,8-DNP on a column for high-performance liquid chromatography.

Environment-dependent conformation and antimicrobial activity of a gramicidin S analog containing leucine and lysine residues

An analog of gramicidin S, cyclo(‐L‐Leu‐L‐Lys‐L‐Leu‐D‐Leu‐L‐Leu‐)2, in which four out of five amino acid components of gramicidin S were substituted, has been synthesized. This analog assumes a conformation similar to that of gramicidin S in acidic liposomes and a random conformation in neutral liposomes. The antimicrobial activity of this analog corresponded to one‐fourth of that of gramicidin S. A possible mechanism for conformational changes in acidic liposomes is discussed.

Conformations and CD curves of cyclo(L- or D-Phe-L-Pro-Aca): cyclized models for specific types of β-bends

β‐Bend CD Measurement Conformational energy calculation Cyclic peptide Gramicidin S NMR measurement

Enhancement of Enantioselectivity in the Optical Resolution of Primary Alcohols with Modified Cyclodextrin Colyophilized Lipase

Abstract Colyophilization of lipase was carried out with immobilized β‐cyclodextrins (β‐CyD) bearing methyl, acetyl, benzoyl, and nicotinoyl substituents. The colyophilizates enhanced stereoselectivity in the acylation of several alcohols. The enantioselectivity in the acylation of ethyl‐1‐hydroxymethyl‐phenylphosphine oxide using colyophilized lipase with nicotinoyl‐β‐CyD increased approximately threefold (from E=34 to E=113). The amphiphilic character of modified CyDs has been found to influence the enhancement of enantioselectivity.

Conformations of chicle(l- or d-Phe-l-Pro-Aca) and chicle(l-Pro-l- or d-Phe-Aca): Cyclized dipeptide models for specific types of β-bends

Abstract Conformational analyses on four cyclic model peptides of the β-bend, chicle( l - or d -Phe- l -Pro-ϵ-aminocaproyl(Aca)) and cyclo( l -Pro- l - or d -Phe-Aca), were carried out both experimentally and theoretically. Chicle( d -Phe- l -Pro- Aca) was shown to exist as a single conformer taking the type II′ β-bend. The comparison of its CD spectra with those of chicle ( l -Ala- l -Ala-Aca) revealed that type I and II′ β-bends, both with α-helix-like CD spectra, can be distinguished. Chicle ( l -Phe- l -Pro-Aca) was shown to exist as a single conformer with a cis l -Phe- l -Pro peptide bond, taking the type VI β-bend. Its CD spectrum has thus been observed for the first time for the bend containing a cis peptide bond. Chicle( l -Pro- l -Phe-Aca) was shown to exist as a mixture of two conformers, the major one taking the type I β-bend with a trans Aca- l -Pro peptide bond and the minor one with a cis Aca- l -Pro peptide bond. Chicle( l -Pro- d -Phe-Aca) was suggested to exist as a mixture of two conformers, the major one taking the type II β-bend with a trans Aca- l -Pro peptide bond and the minor one with a cis Aca- l -Pro peptide bond.