In the current report, the temperature dependence of photoinduced electron transfer between tetrakis-(4-tetram-ethylpyridyl)porphine (T4MPyP) and guanine monophosphate (GMP) has been examined. In the presence of GMP the fluorescence lifetime analysis reveals a Lorentzian distribution of lifetimes centered at 0.7 ns with a width of 0,9 ns displaying significant temperature dependence, Fitting temperature dependent data to the Marcus equation gives a reorganizational energy (lambda) for the electron transfer reaction of 0.6 eV and an electronic coupling factor (H-AB) of 3 x 10(-3) eV. These results suggest conformational regulation of electron transfer within the non-covalent porphyrin:nucleotide complex.