Fluorescence and energy transfer of polypeptides containing naphthyl groups in their side chains

Energy transfer in the singlet state was studied in solution at 25 degrees C for poly(beta-1-naphthylmethyl L-aspartate) and copolymers of beta-1-naphthylmethyl L-aspartate and gamma-benzyl L-glutamate. Transfer efficiencies, migration coefficients, migration lengths, and interaction radii were determined from the quenching studies using biacetyl as a quencher. The migration coefficient increases with increasing naphthyl groups in the copolymers. This means that singlet energy migrates among more naphthyl groups with increasing naphthyl groups in the polymer chain. Interaction radius for the fluorescence quenching by biacetyl was estimated to be in the range of 5.8 to 8.9 A irrespective of whether energy donor is monomer or excimer. Moreover, it was shown that energy migration via excimer does not take place and energy of the excimer is localized.