Fluorescent amino acids as reporter systems in peptido-cyclodextrin inclusion compounds

Abstract

The inclusion behaviour of mono-6-(N-acetyltyrosinyl)amino-6-deoxy-β-cyclodextrin and mono-6-(N-acetyltryptophanyl)amino-6-deoxy-β-cyclodextrin with regard to borneol, menthol and 5-methoxypsoralen have been investigated by fluorescence spectroscopy, circular dichroism and NMR spectroscopy. For mono-6-(N-acetyltryptophanyl)amino-6-deoxy-β-cyclodextrin, the weakly self-included indole residue is disincluded, and for 5-methoxypsoralen, fluorescence resonant energy transfer is observed. In contrast, for mono-6-(N-acetyltyrosinyl)amino-6-deoxy-β-cyclodextrin the self-inclusion is sufficiently strong that no disinclusion occurs. A binary complex is postulated to arise from hydrogen bonding between borneol and mono-6-(N-acetyltyrosinyl)amino-6-deoxy-β-cyclodextrin.