Photophysical and photochemical studies of chlorophyll a and cobalt(II)tetraphenylporphyrin in poly(l-glutamate)-decylammonium ion complex

Spectroscopic studies were carried out on chlorophyll a and cobalt(II)tetraphenylporphyrin solubilized in a poly(l-glutamate) (Poly(Glu))-decylammonium chloride (DeAC) complex system, in the presence of methylviologen (MV2+). The cooperative binding occurred between the anionic Poly(Glu) and the cationic DeAC, leading to the formation of micelle-like hydrophobic clusters of DeAC and also the change in conformation of the Poly(Glu) from the random coil to the α-helix. All of the absorption spectra, the fluorescence quantum yields and the fluorescence lifetimes indicated the existence of equilibrium between the aggregated biofunctional molecules in the bulk phase and the monomeric species in the complex phase of the Poly(Glu)–DeAC solution. The fluorescence quenching of the biofunctional molecules by methylviologen indicates that the conformation-dependent electron transfer occurs in the complex phase.