Size-responsive differential modulation in α-amylase by MPA-CdSe QDs: multispectroscopy and molecular docking study.

QDs has been deftly explored, studied, and optimized because of its unique optical and physicochemical properties. However, their high production and usage arouses the concern of accidental or unavoidable release in environment which can have toxic impact on animals. It is thus indispensable to comprehend its non-target effect. In the present study, interaction of vital digestive enzyme α-amylase was investigated with water-soluble mercaptopropionic acid (MPA)-capped CdSe QDs of five different sizes (1.9 nm, 2.3 nm, 2.5 nm, 3.3 nm, and 3.9 nm) by various spectroscopic techniques. Distinctive increase in absorption spectra and fluorescence quenching of α-amylase was observed chiefly due to α-amylase-CdSe QDs ground state complex formation. Binding constant (Kb), binding sites (n), and quenching constant (Ksv) were also determined. The results illustrated that binding of α-amylase with CdSe QDs followed 1:1 stoichiometry and induced conformational changes in dose- and size-dependent manner. Effect on α-amylase activity in complex form with size varied CdSe QDs suggested higher inhibition of enzymatic activity by smaller size QDs as compared to larger size. Molecular docking of MPA ligand with α-amylase revealed that interaction was majorly driven by hydrophobic forces. It further suggested that MPA did not interact with active site of α-amylase, thus acting as non-competitive inhibitor. The study thus involved a comprehensive analysis of the structural and functional modulation in α-amylase by interaction with hydrophilic MPA-capped CdSe QDs of different sizes. [ABSTRACT FROM AUTHOR]