The binding interaction between cadmium-based, aqueous-phase quantum dots with Candida rugosa lipase

Area of Science:

• Biomaterials Science
• Biochemistry
• Toxicology

Background:

• Quantum dots (QDs) are promising biolabeling materials with potential applications.
• The toxicity of QDs to biological organisms is a significant concern requiring further investigation.

Purpose of the Study:

• To investigate the molecular mechanisms behind structural and activity alterations in Candida rugosa lipase (CRL) upon binding with 3-mercaptopropionic acid-capped CdTe QDs.
• To elucidate the in vitro toxicity of QDs on protein structure and function.

Main Methods:

• Spectroscopic methods (fluorescence quenching)
• Isothermal titration calorimetry (ITC)
• Enzyme activity assays

Main Results:

• CdTe QDs statically quenched CRL's intrinsic fluorescence, indicating binding.
• QDs bind to CRL via hydrophobic interactions, causing protein unfolding, loosening of the skeleton, and secondary structure changes.
• QDs enter the CRL pocket, interacting with Ser-209 and surrounding residues, exposing the catalytic triad and inhibiting enzyme activity by ~15%.

Conclusions:

• 3-mercaptopropionic acid-capped CdTe QDs can negatively affect Candida rugosa lipase.
• This study provides a molecular mechanism for QD-induced toxicity in proteins.
• In vitro analysis is crucial for understanding QD-protein interactions and potential biological impacts.