Chiral discrimination between d- and l-tryptophan based on the alteration of the fluorescence lifetimes by the chiral additives

The chiral microenvironmental properties of bovine serum albumin, cyclodextrins and their mixtures were comparatively investigated based on pyrene as the fluorescence probe. On this basis, a time resolved fluorescence technique to discriminate d- and l-tryptophan (Trp) without separation was developed. This method was based on the quenching rate difference between d- and l-Trp to pyrene in various media including bovine serum albumin, cyclodextrins and their mixtures. Pyrene, tryptophan and bovine serum albumin (or cyclodextrin) could form ternary complexes, which provided a possibility for the discrimination of d- and l-Trp enantiomers. The results indicated that the chiral discrimination of Trp enantiomers could be obtained in the mixture system of γ-cyclodextrin and BSA system, in which the fluorescence lifetime difference (Δτ) and the lifetime difference percentage (Δτ/τ) were 55.8 ns and 28.50%, respectively.