Abstract
The extent of adsorption (Γ) of bovine serum albumin (BSA), β‐lactoglobulin, lysozyme, gelatin, and DNA from aqueous solution onto the hydrophilic surface of cellulose has been measured as function of biopolymer concentration at different temperatures, pHs, and ionic strengths, and in the presence of a high concentration of inorganic salts and denaturants. In all cases, the value of Γ increases with the increase of biopolymer concentration (X~2~) in bulk and it attains a maximum value at a critical mole fraction concentration X. The value of Γ depends upon the nature of protein, temperature, pH, and ionic strength, as well as the nature of neutral salts present in excess. Γ for proteins at a fixed physicochemical condition stands in the following order:
The isotherms for adsorption of DNA nucleotides on cellulose surface at pH 4.0 have been compared at different temperatures and ionic strengths, and in the presence of high concentration of inorganic salts LiCl, NaCl, KCl, and Na~2~SO~4~. Values of Γ for different systems have been evaluated and critically compared. At pH 6.0 and 8.0, Γ values of DNA nucleotides on cellulose are all negative due to the excess positive hydration of cellulose. At pH 4.0, adsorption of nucleotides of acid, alkali, and heat‐denatured DNA widely differ from each other and in the presence of excess concentration of urea becomes negative. The probable mechanisms of biopolymer–cellulose adsorption in terms of polymer hydration, steric interaction, London–van der Waals, hydrophobic, and other types of interactions have been discussed qualitatively. The standard free energy change for the adsorption of protein and DNA nucleotides on the cellulose surface at the state of adsorption saturation has been calculated in kJ per kg of cellulose using an integrated form of the Gibbs adsorption equation. The relation between Δ__G__° and maximum affinities between biopolymers and the polysaccharide interface have been discussed for various systems. © 2005 Wiley Periodicals, Inc. Biopolymers 77: 286–295, 2005