Masaru Shin

The core and complementary sequence responsible for biological activity of the diapause hormone of the silkworm, Bombyx mori

To evaluate the structure-function relationship of the diapause hormone of the silkworm, Bombyx mori, the entire molecule and selected fragment and deleted analogues were chemically synthesized to compare their biological activity. The C-terminal pentapeptide amide was the shortest fragment that elicited 11% diapause eggs at maximum, indicating that this sequence is the core-active structure required for a biological response. The full biological response of about 70% diapause eggs was expressed by the C-terminal hexapeptide amide. However, an ED50 value of this peptide amide was 1000-fold higher than that of the parent molecule. The serial elongation of peptide chain lengths toward the N-terminus brought about the sudden decrease in ED50 values at two positions between Arg9-Gly10 and Thr1-Asp2. The deletion of duplicated sequence(s) located in the middle part of the molecule or the truncation of N-terminal region of the parent molecule increased ED50 values but had no effects on response. Thus, N-terminal region and duplicated sequences act as the complementary structures for full potency of diapause hormone.

Formation and degradation of urea derivatives in the azide method of peptide synthesis. Part 1. The curtius rearrangement and urea formation

The azide method of peptide synthesis (R1CON3+ R2NH2→ R1CO·NHR2) has been investigated with respect to the effect of reaction conditions especially on the formation of urea derivatives (R1NH·CO·NHR2) as side products. Z-Gly-Phe-N3 and H-Gly-OBut were used as model compounds for R1CON3 and R2NH2, respectively, and the rate of formation of peptide was compared with that of urea under various conditions. Peptide formation was estimated from the consumption of R2NH2 and urea formation by the extent of the rate-determining Curtius rearrangement (R1CON3→ R1NCO + N2). Data have also been obtained for other azides and amines. The results show that the conditions currently used in azide couplings (ca. 0.1 M-solutions and 0–5 °C) are generally adequate for minimising the side reaction. On the other hand, some urea derivatives, including Boc-Gly-Tyr-Ser-NH·CH(CH2·CH2·SMe)·NH·CO-Glu(OBut)-His-Phe-Arg-Trp-Gly-OH (6) and Z-Lys(Boc)-Pro-Val-Gly-NH·CH-([CH2]4·NH-Boc)·NH·CO-Lys(Boc)-Arg-Arg-NH2(5) can be synthesised from R1NCO and R2NH2. These ureas have been compared with the corresponding peptides in terms of chromatographic behaviour; the results suggest that when R1and R2are fairly large and complex as in (5) and (6) the separation of peptide from urea will present considerable difficulties.