Biomimetic interactions of proteins with functionalized cadmium sulfide quantum dots

Interactions between various modified semiconductor nanocrystal, cadmium sulfide quantum dots (CdS QDs) and bovine serum albumin (BSA) and lysozyme (LZY) were investigated. CdS QDs capped with mercaptoethanol (MPA), l-cysteine (Lcys) and glutathione (GSH) were synthesized in aqueous solution and characterized by UV–vis and fluorescence spectrum. Circular dichroism (CD) and fluorescence spectrum were used to detect the interactions between as-prepared CdS QDs and protein molecules. The interaction parameters, including binding constant (Kb), binding site number (n) and quench constant (Kq), were determined by fluorescence spectrum. The changes of secondary structures of the proteins were detected by CD. The results imply that CdS QDs modified by different agents have dramatically different binding strength with protein molecules. The results obtained here analyze the biosafety of CdS QDs in terms of the biological behavior of biomolecules and could serve as basis for the application of CdS QDs to bioscience.

Interactions between three different capped (MPA, GSH, Lcys) CdS QDs and two proteins (BSA and LZY) were investigated by fluorescence spectrum and circular dichroism (CD).Figure optionsDownload as PowerPoint slideHighlights
► Interactions between three modified CdS QDs and two proteins were investigated.
► MPA, GSH and Lcys capped CdS QDs showed different affinity to proteins.
► GSH capped CdS QDs showed weakest quenching effects.
► All three CdS QDs could change the microenvironment of Tyr residues in proteins.
► Second structures of proteins changed differently with addition of three CdS QDs.