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Synthesis and conformational study of poly(Nδ-carbobenzoxy, Nδ-benzyl-L-ornithine) and poly(Nδ-benzyl-L-ornithine)

✍ Scribed by Hiroyuki Yamamoto; Tadao Hayakawa; Jen Tsi Yang

Publisher
Wiley (John Wiley & Sons)
Year
1974
Tongue
English
Weight
438 KB
Volume
13
Category
Article
ISSN
0006-3525

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✦ Synopsis

Abstract

Poly(N^δ^‐carbobenzoxy, N^δ^‐benzyl‐L‐ornithine) (PCBLO) was prepared by the standard NCA method. PCBLO was converted into poly(N^δ^‐benzyl‐L‐ornithine) (PBLO) through decarbobenzoxylation with hydrogen bromide. The monomer N^δ^‐benzyl‐L‐ornithine was synthesized by reacting L‐ornithine with benzaldehyde, followed by hydrogenation. The conformation of the two polypeptides was studied by optical rotatory dispersion and circular dichroism. PCBLO forms a right‐handed helix in helix‐promoting solvents. In mixed solvents of chloroform and dichloroacetic acid (DCA) it undergoes a sharp helix–coil transition at 12% (v/v) DCA at 25°C, as compared with 36% for poly(N^δ^‐carbobenzoxy‐L‐ornithine) (PCLO). Like PCLO, the helix–coil transition is “inverse,” that is, high temperature favors the helical form. PBLO is soluble in water at pH below 7 and has a “coiled” conformation. In 88% (v/v) 1‐propanol above pH (apparent) 9.6 it is completely helical. In 50% 1‐propanol the transition pH (apparent) is about 7.4; this compares with a pH~tr~ of about 10 for poly‐L‐ornithine in the same solvent.

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