Comparison of the solid-matrix luminescence properties and photophysical parameters of two products from benzo(a)pyrene-DNA adducts.

The solid-matrix luminescence properties and several calculated photophysical parameters of two important products from the benzo(a)pyrene-DNA adducts were compared. The products were benzo(a)pyrene-r-7,t-8,9,c-10-tetrahydrotetrol (I-1) and 7R,8S,9S-trihydroxy-10R-(N2-deoxyguanosyl-3'-phosphate)-7,8,9,10- tetrahydrobenzo(a)pyrene (BPDE-dG). The solid-matrix luminescence data were obtained for I-1 and BPDE-dG adsorbed on two different solid matrices, namely, 1% alpha-cyclodextrin (CD)/NaCl and 25% trehalose/NaCl and at two different temperatures (93 K and 296 K). The 25% trehalose/NaCl gave higher fluorescence and phosphorescence quantum yields from both I-1 and BPDE-dG in contrast to the 1% alpha-CD/NaCl matrix. The BPDE-dG showed lower fluorescence quantum yields on the solid matrices compared to I-1. The lower fluorescence quantum yields for BPDE-dG were attributed to a photoinduced electron transfer mechanism. In contrast to the room-temperature solution fluorescence of BPDE-dG, BPDE-dG gave rather high fluorescence quantum yields at room temperature when adsorbed on the two solid matrices. From solid-matrix luminescence quantum yields and solid-matrix luminescence lifetimes, many photophysical parameters were calculated and compared. Several differences among the rate constants were noted with the two solid matrices for BPDE-dG and I-1. For example, BPDE-dG showed internal conversion at 296 K with 25% trehalose/NaCl, but no internal conversion was observed at 93 K with this solid matrix. Also, for BPDE-dG the phosphorescence rate constants at 296 K and 93 K were very small with 25% trehalose/NaCl, but the intersystem crossing rate constants from the triplet state to the ground state were very large.(ABSTRACT TRUNCATED AT 250 WORDS)