AVS 53rd International Symposium
    Biomaterial Interfaces Friday Sessions
       Session BI-FrM

Paper BI-FrM3
Volumetric Interpretation of Protein Adsorption: Partition Coefficients, Interphase Volumes, and Free Energies of Adsorption to Hydrophobic Surfaces

Friday, November 17, 2006, 8:40 am, Room 2014

Session: Biomolecular Surface Characterization II
Presenter: H. Noh, Penn State University
Authors: E. Vogler, Penn State University
H. Noh, Penn State University
Correspondent: Click to Email
Interpretive mass-balance equations were derived from a model premised on the idea that protein reversibly partitions from bulk solution into a three-dimensional (3D) interphase volume separating the physical adsorbent surface from bulk solution. Theory was shown to both anticipate and accommodate adsorption of all proteins to the two test surfaces, suggesting that the underlying model was descriptive of the essential physical chemistry of protein adsorption. Application of mass balance equations to experimental data permitted quantification of partition coefficients P, interphase volumes V,@footnote 1@ and the number of hypothetical layers M occupied by protein adsorbed within V.@footnote 2@ Partition coefficients measure the equilibrium ratio of interphase and bulk-solution-phase w/v (mg/mL) concentrations W@footnote 3@ and W,@footnote 4@ respectively, such that P-W@footnote 5@/W.@footnote 6@ Proteins studied were found to be weak biosurfactants with 45< P <520 and commensurately low apparent free-energy-of-adsorption, (-6RT<@footnote 7@G@footnote 8@=-RTlnP<-4RT). These measurements corroborate independent estimates obtained from interfacial energetics of adsorption (tensiometry) and are in agreement with thermochemical measurements for related proteins by hydrophobic-interaction chromatography. Proteins with molecular weight MW<100kDa were found to occupy a single layer at surface saturation whereas the larger proteins IgG and Fib required two layers. @FootnoteText@ @footnote 1@sub I@footnote 2@sub I@footnote 3@sub I@footnote 4@sub B@footnote 5@sub I@footnote 6@sub B@footnote 7@DELTA@footnote 8@sub ads.