Quantum dots are rapidly becoming biomedical researchers' tool of choice for adding a fluorescent label to a wide variety of biomolecules.
Now, thanks to work from a multi-institutional team of investigators, researchers may have a simple, generic method for attaching quantum dots to proteins in a highly controlled manner. Amy Blum, Ph.D., of the Naval Research Laboratory, led this team, which published its results in the journal Nanotechnology.
The investigators took advantage of the fact that quantum dots bind strongly to short peptides containing the amino acid histidine, and that such histidine-containing peptides bind strongly to regions of a protein that contain the amino acid lysine. The researchers start by first mixing a commercially available histidine-containing peptide with the protein they want to label – in this paper, the researchers used an antibody and a virus particle as their target proteins. They then add water-soluble cadmium selenide/zinc sulfide quantum dots to the modified protein, let the mixture sit at room temperature for two days, and then remove the unreacted quantum dots using either gel electrophoresis for small batches or size exclusion chromatography for larger batches.
Experiments with the virus particle showed that quantum dot labeling was uniform and controlled using this method. The researchers observed that this method prevented the formation of quantum dot-protein aggregates, a common occurrence using other labeling techniques. The researchers note that while other investigators obtained similar results using proteins that had been engineered to have histidines available to bind quantum dots, this new method uses off-the-shelf chemicals rather than laboriously engineered proteins to achieve the same end.