Competition between energy transfer and deactivation during quenching of tryptophan fluorescence of albumin by dye molecules

Using quenching of Trp fluorescence by different dyes, bound to bovine seru m albumin, it is shown that the spectral overlap between emission and absor ption spectra does not necessarily lead to energy transfer as the sole quen ching mechanism. A correlation of the limiting quenching value with the For ster overlap integral was not observed. The energy transfer efficiency was less than the quenching efficiency because of competitive radiationless dea ctivation processes induced by dye binding.