Based on the semiclassical model of the electron transfer, kinetic parameters of the electron transfer between tryptophan and tyrosine have been calculated by using the AM1 semi-empirical method. Optimization of the systems of the donor,the acceptor,and the bridge has been performed. A linear reaction coordinate R is used in the construction of the double-well potential for the intermolecular electron transfer from phenol anion radical to indole radical. It has been found that the crossing of the two diabatic potential energy surfaces appears at R=(约等于)0.10. The inner reorganization energy and the exothermicity of the reaction are then determined. Closed shell HF SCF calculations have been carried out for the systems Tryptophy1-Tyrosine and Tyrosyl-Tryptophan for different values of R, and the Koopmans^，theorem is invoked to estimate the energy level splitting A(三角形).From the obtained A(三角形)~m~i~n, the values of electron transfer matrix element V~D~A are determined to be 0.96kJ. mol^-^1 and 0.87kJ.mol^-^1 for Tryptophyl-Tyrosine and Tyrosyl- Tryptophan, respectively.The solvent reorganization energy has been estimated to be 64.60kJ.mol^-^1 according to Marcus^,two-spherical model.

Key words: TYROSINE, TRYPTOPHAN, PEPTIDE, GEOMETRICAL ISOMERISM