CHIRAL DISCRIMINATION IN THE FLUORESCENCE QUENCHING OF PYRENE COMPLEXED TO BETA-CYCLODEXTRIN

Chiral discrimination was observed for the quenching by D- and L-trypt ophan of excited singlet pyrene when complexed to beta-CD in the prese nce of alcohols or short chain alkyl sulfates. Alcohols or alkyl sulfa tes were added to increase the association constant of pyrene with bet a-cyclodextrin. In all cases the quenching by D-tryptophan is more eff icient than for L-tryptophan. The largest discrimination was observed in the presence of tert-butanol (K-sv(D)/K-sv(L)) = 3.6) owing to a ma rked decrease of the quenching efficiency by L-tryptophan. Quenching o ccurs through a static mechanism indicating that pyrene and tryptophan are in close proximity within the cyclodextrin complex.