Fluorescence anisotropy of protein - gold nanoclusters

Red-emitting gold nanoclusters (BSA-Au-25) have been synthesized in Bovine Serum albumin and found to have a characteristic fluorescence lifetime of 1.25 mu s. Fluorescence anisotropy measurements of BSA-Au-25 reveal a dramatic increase in protein size as the pH is reduced from 7 to 3.1, consistent with the change of BSA from N form to E form. This study suggests the possibility of exploiting fluorescent protein-gold nanoclusters to probe protein conformational changes in response to the local environment