Tadatoshi Yamaguchi

Generation of free radicals from dihydropyranzines with DNA strand-breakage activity

ESR spin-trapping techniques revealed that free radical species were generated in a buffer solution (pH7.1) of compounds (1∼5) having a dihydropyrazine skeleton. Oxygen radicals and several carbon-centered radicals were detected as adducts of spin traps: DMPO and DBNBS. Secondary and tertiary radicals trapped were assigned to the carbon-centered radical structures.

New compounds derived from dihydropyrazines having DNA strand-breakage activity

Abstract Dihydropyrazine derivatives such as 2,3-dihydro-5,6-dimethylpyrazine (1), 2,3-dihydro-2,5,6-trimethyl-pyrazine (2) and 2,3-dihydro-2,2,5,6-teramethylpyrazine (3) were found to be transformed into (2R∗, 3S∗, 5R∗)-1,2 ethylene-imino-1,7,10-triaza-2,3,6-trimethyl-3-hydroxy-spiro [4,5] decan-6-ene (4), the stereo-isomeric mixtures of 2,4aR∗,7,9aS∗-tetramethylcyclohexano [1,2-e: 4,5-e′]-dipiperazin-6-ene (5) and (4aR∗, 9aS∗)-2,2,4a,7,7,9a-hexamethylcyclohexano [1,2-e: 4,5-e′]-dipiperazin-6-ene (6), respectively. These dimerized compounds (4, 5 and 6), whose structures were determined by X-ray and nmr spectral analyses, showed almost the same DNA strand-breakage activity as their parent dihydropyrazines. The dimerization pathway is discussed on the basis of the PM3 calculation data.

Cloning, Sequence Analysis, and Expression of the Gene Encoding Sphingomonas paucimobilis FP2001 α- L -Rhamnosidase

The gene (rhaM) encoding the α-L-rhamnosidase of Sphingomonas paucimobilis FP2001 was cloned, sequenced, and expressed in Escherichia coli. The rhaM consisted of 3,354 nucleotides and had a promoter and Shine-Dalgarno sequences typical in bacteria. The rhaM encoding a protein (Rham) deducted from the sequence consisted of 1,117 amino acids and had a putative signal peptide of 25 amino acids. Rham has no similarity to other known rhamnosidases. Rham has a sugar-binding domain of glycoside hydrolase family 2, which has been well conserved in β-glucuronidase, β-mannosidase, and β-galactosidase, in its C-terminal region. Rham is possibly a member of a new bacterial subfamily in glycoside hydrolase family 78 (α-L-rhamnosidase). RT-PCR analysis of rhaM mRNA indicated that the induction of α-L-rhamnosidase by the addition of L-rhamnose occurred on the transcriptional level.

Structure-activity relationships in the induction of single-strand breakage in plasmid pBR322 DNA by amino sugars and derivatives

Structure-activity relationships in the induction of strand breakage in plasmid pBR322 DNA by amino sugars and their derivatives were investigated using agarose gel electrophoresis. The coexistence of a potential free aldehyde group at the C-1 position and a free amino group at the C-2 position in the molecules was indispensable for the display of DNA strand-breaking activity in both mono- and oligo-aminosaccharides. The activity was increased by the introduction of an acidic group, especially a phosphate group, at the C-6 position. The activity was also increased by the addition of Cu2+. The order of activity of the amino monosaccharides tested was D-isoglucosamine > D-mannosamine > D-galactosamine > D-glucosamine, and it is suggested that this order is correlated with the portion of acyclic (aldehydo) form in the solution of each sugar. The possible chemical basis for DNA strand breakage by amino sugars is discussed.

Reaction of 2,3-butanedione with propylenediamine observed by 1H-NMR spectroscopy

2,3-Butanedione reacted with propylenediamine to form an initial intermediate: acetylated methyl-N-(3-aminopropyl) imine, which was a geometrical mixture of syn - and anti- isomers. The intermediate isomerized to anti- orsyn-form via pyrimidine ring flip on heating. A steric factor of the isomers affected the formation of the final products. The mechanism based on NMR spectroscopy and molecular orbital calculation is proposed.