Baranova L A, Volotovskiĭ I D
Biofizika. 1978 Jan-Feb;23(1):152-3.
Using energy transfer from 4-aminobenzene-sulfonamide triplet level to tryptophanyl one of the main energy contributions to trypsin and chymotrypsin inactivation at the temperature of liquid N2 has been shown to make singlet excited state of their tryptophanyls.