title: Capillary electrophoretic studies on displacement and proteolytic cleavage of surface bound oligohistidine peptide on quantum dots.
abstract: Subtle changes in the chemical structure or the composition of surface bound ligands on quantum dots (QDs) remain difficult to detect. Here we describe a facile setup for fluorescence detection coupled capillary electrophoresis (CE-FL) and its application in monitoring ligand displacement on QDs through metal-affinity driven assembly. We also describe the use of CE-FL to monitor amide bond cleavage by a specific protease, based on Förster resonance energy transfer (FRET) between Cy5 and QDs spaced by a hexahistidine peptide (H6-Cy5). CE-FL allowed separation of unbound QDs and ligand bound QDs and also revealed an ordered assembly of H6-Cy5 on QDs. In a ligand displacement experiment, unlabeled hexahistidine peptide gradually displaced surface bound H6-Cy5 until finally reaching equilibrium. The displacement intermediates were clearly separated on CE-FL. Proteolytic cleavage of surface bound H6-Cy5 by thrombin was monitored by CE-FL through mobility shift, peak broadening, and FRET changes. Enzymatic parameters thus obtained were comparable with those measured by fluorescence spectroscopy.
authors: Department of Chemistry, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, PR China. minuswan@gmail.com
authors: Jianhao
authors: J
authors: Wang
authors: Jiang
authors: J
authors: Xia
mesh_terms: D002232:Carbocyanines / Q000737:chemistry; D019075:Electrophoresis, Capillary; D031541:Fluorescence Resonance Energy Transfer; D005978:Glutathione / Q000737:chemistry; D006639:Histidine / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D059748:Proteolysis; D045663:Quantum Dots; D013499:Surface Properties; D013917:Thrombin / Q000378:metabolism
chemical_list: D002232:Carbocyanines; C471213:His-His-His-His-His-His; D009842:Oligopeptides; C085321:cyanine dye 5; D006639:Histidine; D013917:Thrombin; D005978:Glutathione