title: Effect of copper oxide nanoparticles on the conformation and activity of β-galactosidase.
abstract: The primary objective of this study is to explore the interaction of β-galactosidase with copper oxide nanoparticles (CuO NPs). Steady-state absorption, fluorescence and circular dichroism (CD) spectroscopic techniques have been employed to unveil the conformational changes of β-galactosidase induced by the binding of CuO NPs. Temperature dependent fluorescence quenching results indicates a static quenching mechanism in the present case. The binding thermodynamic parameters delineate the predominant role of H-bonding and van der Waals forces between β-galactosidase and CuO NPs binding process. The binding was studied by isothermal titration calorimetry (ITC) and the result revealed that the complexation is enthalpy driven, the ΔH°<0, ΔS°<0 indicates the formation of hydrogen bonds between β-galactosidase and CuO NPs occurs. Disruption of the native conformation of the protein upon binding with CuO NPs is reflected through a reduced functionality (in terms of hydrolase activity) of the protein CuO NPs conjugate system in comparison to the native protein and CuO NPs exhibited a competitive mode of inhibition. This also supports the general belief that H-bond formation occurs with NPs is associated with a lesser extent of modification in the native structure. Morphological features and size distributions were investigated using transmission electron microscopy (TEM) and dynamic light scattering (DLS). Additionally the considerable increase in the Rh following the addition of CuO NPs accounts for the unfolding of β-galactosidase. Chemical and thermal unfolding of β-galactosidase, when carried out in the presence of CuO NPs, also indicated a small perturbation in the protein structure. These alterations in functional activity of nanoparticle bound β-galactosidase which will have important consequences should be taken into consideration while using nanoparticles for diagnostic and therapeutic purposes.
authors.affiliation: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202 002, India.
authors.forename: Gulam
authors.initials: G
authors.lastname: Rabbani
authors.affiliation: School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor DE 43600, Malaysia.
authors.forename: Mohd Jahir
authors.initials: MJ
authors.lastname: Khan
authors.affiliation: Indian Institute of Toxicology Research, Post Box No. 80, Mahatma Gandhi Marg, Lucknow 226 001, India.
authors.forename: Abrar
authors.initials: A
authors.lastname: Ahmad
authors.affiliation: School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor DE 43600, Malaysia.
authors.forename: Mohamad Yusof
authors.initials: MY
authors.lastname: Maskat
authors.affiliation: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202 002, India. Electronic address: rizwanhkhan@hotmail.com.
authors.forename: Rizwan Hasan
authors.initials: RH
authors.lastname: Khan
mesh_terms: D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D019791:Guanidine / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D013816:Thermodynamics; D001616:beta-Galactosidase / Q000737:chemistry*
chemical_list: D003300:Copper; D001616:beta-Galactosidase; D019791:Guanidine; C000520:cuprous oxide
keywords: Circular dichroism; Copper oxide nanoparticles; Dynamic light scattering; Guanidinium hydrochloride unfolding; Hydrolase activity; Thermal denaturation; β-Galactosidase