Peptide-labeled quantum dots for imaging GPCRs in whole cells and as single molecules.
We report a robust and practical method for the preparation of water-soluble luminescent quantum dots (QDs) selectively coupled through an amine or thiol linkage to peptide ligands targeted to G-protein coupling receptors (GPCRs) and demonstrate their utility in whole-cell and single-molecule imaging. We utilized a low molecular weight ( approximately 1200 Da) diblock copolymer with acrylic acids as hydrophilic segments and amido-octyl side chains as hydrophobic segments for facile encapsulation of QDs (QD 595 and QD 514) in aqueous solutions. As proof of principle, these QDs were targeted to the human melanocortin receptor (hMCR) by chemoselectively coupling the polymer-coated QDs to either a hexapeptide analog of alpha-melanocyte stimulating hormone or to the highly potent MT-II ligand containing a unique amine. To label QDs with ligands lacking orthogonal amines, the diblock copolymers were readily modified with water-soluble trioxa-tridecanediamine to incorporate freely available amine functionalities. The amine-functionalized QDs underwent facile reaction with the bifunctional linker NHS-maleimide, allowing for covalent coupling to GPCR-targeted ligands modified with unique cysteines. We demonstrate the utility of these maleimide-functionalized QDs by covalent conjugation to a highly potent Deltorphin-II analog that allowed for selective cell-surface and single-molecule imaging of the human delta-opioid receptor (hDOR).
Zhou
Min
M
Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041, USA.
Nakatani
Eri
E
Gronenberg
Luisa S
LS
Tokimoto
Takahira
T
Wirth
Mary J
MJ
Hruby
Victor J
VJ
Roberts
Amber
A
Lynch
Ronald M
RM
Ghosh
Indraneel
I
D002478:Cells, Cultured / Q000378:metabolism; D005453:Fluorescence; D006801:Humans; D007124:Immunoenzyme Techniques; D007668:Kidney / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry; D008668:Metallothionein / Q000737:chemistry / Q000378:metabolism; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D011108:Polymers / Q000737:chemistry; D045663:Quantum Dots; D044105:Receptor, Melanocortin, Type 4 / Q000737:chemistry / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry*; D017465:Receptors, Opioid, delta / Q000737:chemistry / Q000378:metabolism
D008051:Lipid Bilayers; C470072:MC4R protein, human; D009842:Oligopeptides; D010446:Peptide Fragments; D011108:Polymers; D044105:Receptor, Melanocortin, Type 4; D043562:Receptors, G-Protein-Coupled; D017465:Receptors, Opioid, delta; C060209:deltorphin II, Ala(2)-; D008668:Metallothionein