title: Interpreting the adsorption of serum albumin and lactoglobulin onto ZnS nanopaticles: effect of conformational rigidity of the proteins.
abstract: The work we have undertaken is to investigate the adsorption of two different proteins (BSA and BLG) having near same IEP and differing in their conformational flexibility, onto the surface of ZnS nanoparticles (ZnS NPs). BSA and BLG both have an IEP value around pH~5. BSA is more prone to conformational deformation and considered "soft" while BLG holds the conformational rigidity and considered as "hard" protein. To ascertain the differences in surface coverage and conformation of the protein onto ZnS surface (PZC ~ 3.7), we have evaluated the adsorption profile at pH 7, where the entire surface behaves negatively. An integrated approach was taken by incorporating zeta (ζ) potential, fluorescence and CD for analyzing the adsorption process. In both systems, an increase in protein surface coverage was observed with the increase in free protein concentration in the solution and ζ values approaching that of native protein at high surface coverage. An alteration in the tertiary structure was observed for both BSA and BLG. The CD spectra analysis reveals that the secondary structure of the BSA was more deviated from the native protein structure, accommodating the increased adsorption value. For BLG no such prominent structural alteration was observed. These findings help us to understand better, how adjustment of the protein adsorption amount can be achieved onto the surface of nanoparticles having like charges.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India.
authors.forename: Jiban
authors.initials: J
authors.lastname: Saikia
authors.affiliation: Centre for the Environment, Indian Institute of Technology Guwahati, Assam 781039, India.
authors.forename: Bedabrata
authors.initials: B
authors.lastname: Saha
authors.affiliation: Department of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India; Centre for the Environment, Indian Institute of Technology Guwahati, Assam 781039, India. Electronic address: gdas@iitg.ernet.in.
authors.forename: Gopal
authors.initials: G
authors.lastname: Das
mesh_terms: D000327:Adsorption; D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007782:Lactoglobulins / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D055672:Static Electricity; D013440:Sulfides / Q000737:chemistry; D013499:Surface Properties; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D007782:Lactoglobulins; D013440:Sulfides; D017967:Zinc Compounds; D012710:Serum Albumin, Bovine; C031238:zinc sulfide
keywords: BSA; Hard and soft proteins; Protein adsorption; ZnS nanoparticle; β-Lactoglobulin