title: Stability of proteins on hydrophilic surfaces.
abstract: The physical and chemical properties of solid substrates or surfaces critically influence the stability and activity of immobilized proteins such as enzymes. Reports of increased stability and activity of enzymes near/on surfaces as compared with those in solution abound; however, a mechanistic understanding is wanting. Simulations and experiments are used here to provide details toward such a mechanistic understanding. Experiments demonstrate increased activity of alcohol dehydrogenase (ADH) inside moderate hydrophilic mesopourous silica (SBA-15) pores but drastically decreased activity inside very hydrophilic NH2-SBA-15 surfaces as compared with that in solution. Also, the temperature stability of ADH was increased over that in solution when immobilized in a cavity with a mildly hydrophilic surface. Simulations confirm these experimental findings. Simulations calculated in the framework of a hydrophobic-polar (H-P) lattice model show increased thermal stability of a model 64-mer peptide on positive and zero curvature surfaces over that in solution. Peptides immobilized inside negative curvature cavities (concave) with hydrophilic surfaces exhibit increased stability only inside pores that are only 3-4 nm larger than the hydrodynamic radius of the peptide. Peptides are destabilized, however, when the surface hydrophilic character inside very small cavities/pores becomes large.
authors.affiliation: Howard P. Isermann Department of Chemical and Biological Engineering and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute , Troy, New York 12180-3590, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Grimaldi
authors.forename: Mithun
authors.initials: M
authors.lastname: Radhakrishna
authors.forename: Sanat K
authors.initials: SK
authors.lastname: Kumar
authors.forename: Georges
authors.initials: G
authors.lastname: Belfort
mesh_terms: D000327:Adsorption; D000426:Alcohol Dehydrogenase / Q000737:chemistry*; D057075:Enzyme Assays; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D010455:Peptides / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics
chemical_list: D004800:Enzymes, Immobilized; D010455:Peptides; C509969:SBA-15; D029701:Saccharomyces cerevisiae Proteins; D012996:Solutions; D012822:Silicon Dioxide; C516801:ADH1 protein, S cerevisiae; D000426:Alcohol Dehydrogenase