Quantum Dot Molecules Assembled with Genetically Engineered Proteins

We report the assembly of quantum dots using an approach that attempts to capitalize on the self-assembling properties of naturally occurring proteins. Colloidal quantum dots made of cadmium selenide core and a zinc sulfide shell, (CdSe)ZnS, were incubated with a genetically modified, bacterial cellulosomal protein, cohesin, and the resultant mixture subjected to fractionation using high-pressure size exclusion chromatography (HPSEC). We note that the HPSEC profile is distinctly bimodal. The peak corresponding to particles of larger effective hydrodynamic radius (R_e) contains a plethora of sizable protein-coated, quantum dot assemblies with a predominance of structures that are trefoil-shaped. The fraction corresponding to particles of smaller R _e contains individual, protein-coated quantum dots that are chemically different from their larger counterparts. This overall procedure is shown to successfully assemble novel quantum dot bioconjugates that exhibit light harvesting properties as well as providing an effective method of purifying quantum dot samples.