摘要
A series of polypeptides (CAP n WNs, where n = 3, 6, 10, and 13), mainly composed of consecutive prolines, were covalently anchored onto the surfaces of gold nanoparticles through the terminal cysteine to form Au-S bonds. A tryptophan near the C-terminus of the peptide exposed to water serves as a fluorophore. By changing the number of prolines, the distance between the tryptophan and the gold nanoparticle can be systematically adjusted within the range of 5 nm. The kinetics of the tryptophan fluorescence in pure CAP n WNs at 355-365 nm upon 266 nm excitation is insignificantly accelerated in comparison with that of pure tryptophan. As CAP n WNs are attached onto ca. 13 nm gold nanoparticles, the fluorescence kinetics of tryptophan is drastically accelerated as its distance to the gold nanoparticle surface is shortened. Accounting for the nanosurface energy transfer (NSET) and electron transfer process from the excited state of tryptophan to the gold nanoparticle, an apparent decay factor β attributed to electron transfer is derived as 0.11 Å -1 , referring to a long-distance electron transfer pathway. An additional rate coefficient, attributed to the tryptophan-tryptophan intermolecular energy transfer at a short distance, was also taken into consideration and suggested the close occupancy of CAP n WNs on the nanoparticle surface. Our results further suggested that polyprolines are capable of serving as molecular rulers and molecular wires in conjugating with nanomaterials. (Figure Presented).