Counterion effects in protein nanoparticle electrostatic binding: a theoretical study.
Effects of counterions on the folding conformation of proteins, bound electrostatically on the surface of charge-ligand functionalized nanoparticles, have been investigated based on the protein folding energy calculation. The folding energy of a protein has been taken as a sum of the short range interaction energies, like, the van der Waals attraction and the hydrogen bond energies, and the long range coulomb interaction energy. On electrostatic binding, counterions associated with surface ligands of nanoparticles diffuse into bound proteins through the medium of dispersion. As a result, bound proteins partially unfold, as observed in circular dichroism experiments, which has been realized using the "charge-dipole" and the "charge-induced dipole" interactions of counterions with polar and non-polar residues, respectively. The effect of counterions solvation in the dispersing medium, e.g., water, which causes water molecules to polarize around the counterions, has also been considered. The folding energy of bound proteins has been seen to decrease proportionally with the increasing number of diffusion of counterions and their polarizability.
UGC-DAE Consortium for Scientific Research, Mumbai Centre, Trombay, Mumbai 400085, India. Electronic address: ghoshg@yahoo.com.
Goutam
G
Ghosh
D000818:Animals; D000838:Anions / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D002417:Cattle; D002645:Chickens; D004058:Diffusion; D006860:Hydrogen Bonding; D007768:Lactalbumin / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009113:Muramidase / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D011485:Protein Binding; D017510:Protein Folding; D055672:Static Electricity; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D000838:Anions; D002412:Cations; D014867:Water; D007768:Lactalbumin; D009113:Muramidase
Counterion effects; Dipole and induced-ion interactions; Ion solvation in water; Protein folding energy; Protein–nanoparticle electrostatic binding