Quantum chemical studies on chelation in nano-bio conjugate between ZnO nanoparticles and cellular energy carrier molecules

Nano-bio complexes, made up of nanoparticle and biomolecules, have wide applications in biomedical nanotechnologies. This makes microscopic understanding of such materials important. Here, we carry out quantum chemical calculations based on DFT on nano-bio conjugate between Zn12O12 cluster (ZnONP) and energy carrier biomolecules in cellular environment, like, ATP, ADP and AMP. We focus on microscopic details of chelation by individual groups, namely, phosphate, ribose and adenine of these molecules with ZnONP. Electronic structures and bonding interactions in ground states of all the complexes are presented through the molecular orbital (MO) theory and the natural bond orbital (NBO) analyses as well as the Raman Spectra. DFT-optimized geometries and bond indices suggest presence of Zn–N(adenine) bond and multiple Zn–O(phosphate) bonds. Phosphate groups form additional O–H⋯O non-classical bonds with ZnONP. Kohn-Sham MOs and natural population analyses suggest that the adenine moiety forms a coordinate covalent bond (Zn–N) with ZnONP through adenine → ZnONP charge transfer (CT), while phosphate groups from coordinate covalent bonds (Zn–O) through ZnONP → phosphate CT in all nano-bio complexes, leading to better stability of bio-molecules-ZnONP complex with increasing of number of phosphate groups in the bio-molecules.