title: Capping of CdSe-ZnS quantum dots with DHLA and subsequent conjugation with proteins.
abstract: We provide a detailed protocol for designing water-soluble CdSe-ZnS quantum dots (QDs) based on cap exchange of the native hydrophobic shell with dihydrolipoic acid (DHLA) ligands, and the preparation of functional QD bioconjugates for use in immunoassays. Our conjugation strategy is based on non-covalent self-assembly between DHLA-capped QDs and protein appended with either an electrostatic attachment domain (namely, the basic leucine zipper) or a polyhistidine tag. These bioconjugates combine the properties of the QD and attached biomolecule to create structures with desirable luminescent and biologically specific properties. This method also allows the preparation of mixed surface conjugates, which results in the conjugates gaining multiple biological activities. Conjugation of DHLA-capped QDs to maltose binding protein (MBP), the immunoglobulin-G-binding beta2 domain of streptococcal protein G (PG) and avidin will be described. MBP and PG were modified by genetic fusion with either a charged leucine zipper or a polyhistidine interaction domain.
authors.affiliation: US Naval Research Laboratory, Optical Sciences Division, Code 5611, 4555 Overlook Avenue SW, Washington, DC 20375, USA.
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Clapp
authors.forename: Ellen R
authors.initials: ER
authors.lastname: Goldman
authors.forename: Hedi
authors.initials: H
authors.lastname: Mattoussi
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000378:metabolism*; D001360:Avidin; D001426:Bacterial Proteins; D019187:Cadmium Compounds / Q000737:chemistry*; D002352:Carrier Proteins; D007118:Immunoassay / Q000379:methods*; D058619:Maltose-Binding Proteins; D011506:Proteins / Q000378:metabolism*; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D019187:Cadmium Compounds; D002352:Carrier Proteins; C034284:IgG Fc-binding protein, Streptococcus; D058619:Maltose-Binding Proteins; D011506:Proteins; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; D001360:Avidin; C058667:cadmium selenide; D015126:8,11,14-Eicosatrienoic Acid; C031238:zinc sulfide