Selective fluorometry of cytochrome c using glutathione-capped CdTe quantum dots in weakly basic medium

Glutathione-capped CdTe quantum dots (GSH-CdTe QDs) were synthesized in aqueous medium. Their interactions with proteins, especially three heme-containing proteins, were investigated over a broad pH range. At 6.0∈<∈pH∈<∈8.0, the fluorescence of the GSH-CdTe QDs can be effectively quenched by cytochrome c (Cyt. c) and hemoglobin, respectively. At pH∈>∈8.0, only cytochrome c quenched the fluorescence of the GSH-CdTe QDs, and no significant fluorescence changes were observed for hemoglobin or other proteins. Based on the distinct fluorescence response, a novel method has been developed for the selective determination of cytochrome c using GSH-CdTe QDs as the fluorescence probe at pH 9.0. Under optimum conditions, the linear range of the calibration curve is from 3.2∈×∈10^-8 to 2.4∈×∈10 ^-6∈mol L^-1 and the detection limit is 3.0∈×∈10^-9∈mol L^-1. The method has been applied to the determination of cytochrome c in three synthetic and real samples, and satisfactory results were obtained with QDs through selecting the proper pH value.