Protein adsorption equilibrium model development

A useful literature relating to polypeptide and protein adsorption kinetics and equilibrium behavior in finite bath systems for both affinity and ion-ex-change HPLC sorbents is now available160,169,171-174,228,234 319 323 402"405 and various mathematical models have been developed, incorporating data on the adsorption behavior of proteins in a finite bath.8,160 167-169 171-174 400 403-405 406 One such model, the so-called combined-batch adsorption model (BAMcomb), initially developed for nonporous particles, takes into account the dynamic adsorption behavior of polypeptides and proteins in a finite bath. Due to the absence of pore diffusion, analytical solutions for nonporous HPLC sorbents can be readily developed using this model and its two simplified cases, and the effects of both surface interaction and film mass transfer can be independently addressed. Based on this knowledge, extension of the BAMcomb approach to porous sorbents in bath systems, and subsequently to packed-, expanded-, and fluidized-bed systems, can then be achieved. 

At this stage of developments, most fixed-bed adsorption models assume that film mass transfer resistance is small compared with the other transport resistances in the system and that equilibrium is reached instantaneously between the solute in the pore liquid and at the surface of the sorbent. Even if it assumed that a homogeneous adsorptive HPLC sorbent is used, it can be readily shown, however, that both film and pore diffusion mass transfer resistances cannot be ignored393,394 and that the dynamic behavior of the adsorption stage is greatly dependent on the rate of the polypeptide- or protein-ligate interaction.8,357,395 Breakthrough of solute(s) may thus occur... 

As mentioned above, beside the diffusion-controlled models, others exist to describe the adsorption kinetics and exchange of matter. De Feijter et al. (1987) have developed a relation taking into consideration simultaneous adsorption of proteins and surfactants at an interface. As a special case a relation results which describes the equilibrium state of adsorption of polymer molecules at a liquid interface. 

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