1996 Volume 59 Issue 3 Pages 457-464
Polypeptide having about 50% carbazolyl groups (Poly {γ-[β-(N-carbazolyl) ethyl]-Lglutamate/methyl-L-glutamate} copolypeptide (PC 50 LG)) was synthesized. The molar ellipticity corresponding to the α-helical structure of PC 50 LG was considerably increased by adding the cyanine dye both in solution and in film. This can be attributed to the change in the main chain structure of PC 50 LG and/or the conformation of side chain caused by the interaction between conjugated π-electron of carbazolyl group on PC 50 LG side chain and conjugated π-electron of cyanine dye. The induced circular dichroism (ICD) was also found in the absorption band corresponding to the cyanine dye both for the film and for the solution containing PC 50 LG and cyanine dye. Further, the shape and the magnitude of this ICD significantly varied with the methine length in cyanine dye. Taking the molecular length of the cyanine dyes and the estimated molecular structure of PC 50 LG into account, these results suggest that cyanine dyes interact with carbazolyl groups on α-helical chain of PC 50 LG and the conformation of the cyanine dye·PC 50 LG complex is affected by the methine length in cyanine dye. The photocurrent of cyanine dye-doped PC 50 LG was also examined. Consequently, NK- 76 doped PC 50 LG film, showing the strongest ICD in the present experiment, gave about 10 times larger photocurrent than PC 50 LG film containing no cyanine dye.
