Abstract
The buoyant titrations of ovalbumin in CsCl, RbCl, CsBr and RbBr were measured between pH 2 and 13. The buoyant densities were found to depend on the salt employed to generate the density gradient and the solution pH. At low pH, nearly identical buoyant densities were observed in solutions having a common anion while at high pH, salt solutions having the same cation produced nearly indentical buoyant densities. The buoyant density of ovalbumin in RbBr was found to decrease as the pH was increased from 2 to 6. This is the first demonstration of a drop in the buoyant titration curve for a biopolymer.
A model based on an invariant partial specific volume, normal titration of all amino acid residues, the binding of a counter-ion to each ionized residue and all hydration associated with these salt pairs was constructed and satisfactorily accounted for all four buoyant titration curves. These results indicate that no water is bound to the neutral portion of this protein.
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Graves Pedersen, T., Ifft, J.B. Buoyant titration of ovalbumin in four alkali halides. Hydration and ion binding. Carlsberg Res. Commun. 43, 65 (1978). https://doi.org/10.1007/BF02906504
DOI: https://doi.org/10.1007/BF02906504