Binding of Cytochrome c to CdTe Colloidal Quantum DotsInvestigation of Stoichiometry and Thermodynamics of the Nanohybrid Creation Process.

Protein binding to the colloidal quantum dot (QD) is necessary for the construction of nanobiohybrids. The calculation of stoichiometry may not be simple; QD is a sphere with a uniform surface, and the QD-protein junction may influence protein conformation and shape. Protein shape allows for different packing on the QD surface. Herein, we characterized binding between two types of QDs, differing by their radii, and three versions of a cytochrome c protein, native one, and with 6xHisTag on N- or C-terminus. The average stoichiometry was 2.44/8-9 protein molecules per nanoparticle, depending on QD. The binding of HisTag-proteins to QD was enthalpy-driven, with negative entropy. We verified the binding constants in different methods, allowing the exposition of the different surfaces of cytochrome c for binding.