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Biomedical subjects

T Okuda

Publications and source records attributed to T Okuda.

At least 541 records · Page 30Linked to original sources
PubMed1975

Synthesis of DL- and D-gluco-hept-3-ulose.

DL-gluco-Hept-3-ulose was synthesised by oxidation of tri-O-isopropylidene-meso-glycero-gulo-heptitol with methyl sulphoxide-phosphorus pentaoxide, and subsequent hydrolysis. D-gluco-Hept-3-ulose (3) was synthesised by oxidation of one of the two isopropylidene derivatives from perseitol (D-glycero-D-galacto-heptitol), which is presumed to have the 2,2:4,5:6,7 structure, followed by hydrolysis. The crude product from the reduction of DL-gluco-hept-3-ulose with sodium borohydride showed two peaks corresponding to meso-glycero-gulo-heptitol and perseitol on g.l.c. of the trimethylsilyl derivatives. Isolation and acetylation of the latter heptitol revealed it to be racemic perseitol. Oxodation of DL-gluco-hept-3-ulose with oxygen in alkali followed by treatment with ferric acetate-hydrogen peroxide gave products with chromatographic behaviour characteristic of arabinonolactone and erythrose. Treatment of DL-gluco-hept-3-ulose with 2,4-dinitrophenylhydrazine gave a 1-deoxy-2,4-dinitrophenylosazone.

Heptoses↗
PubMed1975

Titration study of acetylated lysozyme.

To study the interaction between carboxyl groups and amino groups in native lysozyme [EC 3.2.1.17], and to identify the positions and the pK values of the abnormal carboxyl groups, N-acetylated lysozyme was prepared. The acetylation did not affect the molecular shape of the enzyme, but changed six amino groups to a non-ionizable form, leaving one amino group free; this was determined to be Lys 33. In addition, pH titration of the acetylated lysozyme in 0.2 or 0.02 M KCl aqueous solution indicated fewer titratable groups with pK(int) of 7.8 or 10.4 compared with the native protein, though the number of titratable carboxyl groups was not affected by the acetylation. From the pH titration results and structural considerations, the unititratable carboxyl groups were suggested to be Asp 48, Asp 66, and Asp 87. On the other hand, spectrophotometric titration in 0.2 M KCl showed that all three tyrosine residues are titratable in the acetylated protein, although an abnormal tyrosine residue exists in the native state. Tyr 20 was suggested to be untitratable in the pH range of 8-12.6.

Acetylation↗