title: Small-molecule ligands strongly affect the Förster resonance energy transfer between a quantum dot and a fluorescent protein.
abstract: We report herein the study of Förster resonance energy transfer (FRET) between a CdSe/ZnS core/shell quantum dot (QD) capped with three different small-molecule ligands, 3-mercaptopropionic acid (MPA), glutathione (GSH), and dihydrolipoic acid (DHLA), and a hexa-histidine (His(6))-tagged fluorescent protein, mCherry (FP). The Förster radius (R(0)) and the corresponding donor-acceptor distances (r) for each of the QD-FP FRET systems were evaluated by using the Förster dipole-dipole interaction formula. Interestingly, both the FRET efficiency (E) and r were found to be strongly dependent on the capping small-molecule ligands on the QD surface, where E ≈ 85% was obtained at a FP:QD copy number of 2:1 for the MPA capped QD, while that for the DHLA capped QD was <25% under the same conditions. A molecular model was proposed to explain the possible reasons behind these observations. The dissociation constants (K(d)s) and kinetics of the self-assembled QD-FP systems were also evaluated. Results show that the QD-FP self-assembly process is fast (completes in minutes at low nM concentrations), strong (with K(d) ≈ 1 nM) and positively cooperative (with the Hill coefficient n > 1), suggesting that the QD-His(6)-tagged biomolecule self-assembly is a facile, effective approach for making compact QD-bioconjugates which may have a wide range of sensing and biomedical applications.
authors.affiliation: School of Chemistry and Astbury Centre for Structural Molecular Biology, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Haiyan
authors.initials: H
authors.lastname: Zhang
authors.forename: Jeff
authors.initials: J
authors.lastname: Hollins
authors.forename: Michael E
authors.initials: ME
authors.lastname: Webb
authors.forename: Dejian
authors.initials: D
authors.lastname: Zhou
mesh_terms: D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D045663:Quantum Dots
chemical_list: D005456:Fluorescent Dyes; D008024:Ligands