Polypeptides films, optical rotation

When the most common spiropyran SP-4 was mixed in poly(y-benzylglutamate) to prepare a film, a reversible change in optical rotation was observed upon 365 nm light irradiation and visible light irradiation [49], The largest Aa before and after UV irradiation at sodium D-line (589 nm) was 1.225° for 4 mol% concentration. It was supposed that the change might have arisen from the chiral interaction between the chiral polypeptide environment and the colored merocyanine. Indeed, an induced CD was observed. 

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