title: Solution-phase single quantum dot fluorescence resonance energy transfer.
abstract: We present a single particle fluorescence resonance energy transfer (spFRET) study of freely diffusing self-assembled quantum dot (QD) bioconjugate sensors, composed of CdSe-ZnS core-shell QD donors surrounded by dye-labeled protein acceptors. We first show that there is direct correlation between single particle and ensemble FRET measurements in terms of derived FRET efficiencies and donor-acceptor separation distances. We also find that, in addition to increased sensitivity, spFRET provides information about FRET efficiency distributions which can be used to resolve distinct sensor subpopulations. We use this capacity to gain information about the distribution in the valence of self-assembled QD-protein conjugates and show that this distribution follows Poisson statistics. We then apply spFRET to characterize heterogeneity in single sensor interactions with the substrate/target and show that such heterogeneity varies with the target concentration. The binding constant derived from spFRET is consistent with ensemble measurements.
authors.affiliation: Optical Sciences Division, Code 5611, Center for Bio/Molecular Science and Engineering, Code 6900, Naval Research Laboratory, Washington, D.C. 20375, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pons
authors.forename: Igor L
authors.initials: IL
authors.lastname: Medintz
authors.forename: Xiang
authors.initials: X
authors.lastname: Wang
authors.forename: Douglas S
authors.initials: DS
authors.lastname: English
authors.forename: Hedi
authors.initials: H
authors.lastname: Mattoussi
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D002232:Carbocyanines / Q000737:chemistry; D002352:Carrier Proteins / Q000737:chemistry*; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000737:chemistry*; D058619:Maltose-Binding Proteins; D045663:Quantum Dots; D012235:Rhodamines / Q000737:chemistry; D018036:Selenium Compounds / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D002232:Carbocyanines; D002352:Carrier Proteins; D005456:Fluorescent Dyes; D058619:Maltose-Binding Proteins; D012235:Rhodamines; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; C089187:cyanine dye 3; C085321:cyanine dye 5; C058667:cadmium selenide; C031238:zinc sulfide