Structure and Activity of Lysozyme on Binding to ZnO Nanoparticles

• Published in: Langmuir 2010-03, Vol.26 (5), p.3506-3513
• Main Authors: Chakraborti, Soumyananda, Chatterjee, Tanaya, Joshi, Prachi, Poddar, Asim, Bhattacharyya, Bhabatarak, Singh, Surinder P, Gupta, Vinay, Chakrabarti, Pinak
• Format: Article
• Language: English
• Subjects: Anilino Naphthalenesulfonates - metabolism; Animals; Biological Interfaces: Biocolloids, Biomolecular and Biomimetic Materials; Calorimetry; Catalytic Domain; Chemistry; Colloidal state and disperse state; Cross-Linking Reagents - pharmacology; Exact sciences and technology; General and physical chemistry; Glutaral - pharmacology; Guanidine - pharmacology; Hydrogen-Ion Concentration; Models, Molecular; Muramidase - chemistry; Muramidase - metabolism; Nanoparticles - chemistry; Particle Size; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Protein Denaturation - drug effects; Protein Multimerization - drug effects; Protein Structure, Quaternary - drug effects; Protein Structure, Secondary - drug effects; Spectrometry, Fluorescence; Surface physical chemistry; Thermodynamics; Urea - pharmacology; Zinc Oxide - chemistry; Zinc Oxide - metabolism; Zinc Oxide - pharmacology
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la903118c

The interaction between ZnO nanoparticles (NPs) and lysozyme has been studied using calorimetric as well as spectrophotometric techniques, and interpreted in terms of the three-dimensional structure. The circular dichroism spectroscopic data show an increase in α-helical content on interaction with ZnO NPs. Glutaraldehyde cross-linking studies indicate that the monomeric form occurs to a greater extent than the dimer when lysozyme is conjugated with ZnO NPs. The enthalpy-driven binding between lysozyme and ZnO possibly involves the region encompassing the active site in the molecule, which is also the site for the dimer formation in a homologous structure. The enzyme retains high fraction of its native structure with negligible effect on its activity upon attachment to NPs. Compared to the free protein, lysozyme−ZnO conjugates are more stable in the presence of chaotropic agents (guanidine hydrochloride and urea) and also at elevated temperatures. The possible site of binding of NP to lysozyme has been proposed to explain these observations. The stability and the retention of a higher level of activity in the presence of the denaturing agent of the NP-conjugated protein may find useful applications in biotechnology ranging from diagnostic to drug delivery.