[Study on interaction mechanism between meso-tetra-(4-hydroxyphenyl)-Zn porphyrin and bovine serum albumin by fluorescence method].

In the present paper, the binding reaction between meso-tetra-(4-hydroxyphenyl)-Zn porphyrin (TPP-Zn) and bovine serum albumin (BSA) was studied at different temperatures by fluorescence method. It was shown that meso-tetra-(4-hydroxyphenyl)-Zn porphyrin has a strong ability of quenching the fluorescence of bovine serum albumin. Based on the mechanisms of fluorescence quenching of bovine serum albumin caused by meso-tetra-(4-hydroxyphenyl)-Zn porphyrin, the binding constants between meso-tetra-(4-hydroxyphenyl)-Zn porphyrin and bovine serum albumin were measured under different temperatures. The experiment showed that meso-tetra-(4-hydroxyphenyl)-Zn porphyrin and bovine serum albumin have strong interactions. The binding constants of the reaction at 27 degrees C, 35 degrees C and 42 degrees C were 1.521 x 10(6) L x mol(-1), 7.048 x 10(5) L x mol(-1) and 1.473 x 10(5) L x mol(-1), respectively, and were decreased with increasing the temperature. The constants of maximum diffusion collision quenching rate-K(q) were above 2.0 x 10(10) L x mol(-1) x s(-1). Therefore, the sort of quenching between meso-tetra-(4-hydroxyphenyl)-Zn porphyrin and bovine serum albumin was determined as static quenching. By the theory of Förster of non-radiation energy transfer, the binding distance and the energy transfer efficiency at 27 degrees C between meso-tetra-(4-hydroxyphenyl)-Zn porphyrin (accepter of energy) and bovine serum albumin (donor of energy) were obtained, respectively. The binding distance was 3.72 nm, which is less than 7 nm, therefore, the interaction was similar to the non-radiation energy transfer, and the static quenching was further proved. According to the thermodynamic parameters, the main sorts of binding force between meso-tetra-(4-hydroxyphenyl)-Zn porphyrin and bovine serum albumin could be judged as electrostatic force when deltaG < 0, deltaH < 0 and deltaS > 0.