Effect of the ion-protein dispersion interactions on the protein-surface and protein-protein interactions

Abstract

A equação de Poisson-Boltzmann é utilizada para calcular o potencial de campo médio característico das interações entre proteínas. Definimos um parâmetro que permite sua comparação com o segundo coeficiente osmótico do virial obtido de diferentes técnicas analíticas experimentais e fornece informação sobre as interações proteína-proteína ou proteína-superfície. Este parâmetro pode ser relacionado à solubilidade de proteínas ou, ainda, ser utilizado na determinação de condições favoráveis para adsorção de proteínas em superfícies ou agregados protéicos. Os cálculos mostram um acordo razoável com os segundos coeficientes do virial experimentais e revelam que é possível predizer diferentes efeitos de Hofmeister observados experimentalmente para soluções protéicas. Demonstramos que a inclusão dos potenciais de dispersão íon-proteína originários das polarizabilidades dos íons e das proteínas pode explicar as séries de Hofmeister. Em particular, damos a evidência para a inversão da série de Hofmeister em função do pH do meio e do ponto Isoelétrico (pI) da proteína em análise.Interactions between proteins are studied by calculating the potential of mean force based on the Poisson-Boltzmann equation. We define a parameter that allows a comparison between the osmotic second virial coefficients obtained from different experimental analytical techniques and provides information about both protein-protein or protein-surface interactions. It can be related to the protein solubility and be used to determine favorable conditions for protein adsorption on a specific surface or protein aggregation. The calculations show reasonable agreement with the experimental second virial coefficient. They also reveal that it is possible to predict different Hofmeister effects observed experimentally in protein solutions. We demonstrate that the effect of including many-body ion-protein dispersion potentials originating from polarizabilities of ions and proteins may offer an explanation for the Hofmeister series. In particular, we give evidence for the inversion of Hofmeister series as function of pH for a given protein.Keywords: van der Waals interactions, Hofmeister series, protein adsorption, osmotic second virial coefficient IntroductionProtein adsorption and protein precipitation are involved in a wide range of phenomena and applications.The deposition of blood proteins on to medical devices and the subsequent modification of their biological responses, the bacterial fouling of ship hulls and the blockage of filtration membranes in bio-separation processes are examples of unfavorable aspects of protein adsorption. The extensive uses of a variety of proteins in food emulsion stabilization and in the fabrication of biosensors are examples of useful applications. Protein adsorption from biofluids on to solids plays a mediating role in bioaccumulation, systemic foreign body reactions, tissue regeneration, and is, therefore, crucial for biocompatibility and performance of medical devices. In line with colloid theories correlations exist betw...

Interactions in protein mixtures. Part I: Second virial coefficients from osmometry

“…Similar hard sphere behavior has been reported earlier for BSA at high ionic strength, over a wide pH range (Moon, Curtis, et al, 2000). Increased repulsion between proteins at decreasing ionic strength (I) has been discussed in terms of electrostatic double layers (Baussay et al, 2004;Moreira, Bostr€ om, Ninham, Biscaia, & Tavares, 2007;Walstra, 2003). Fig.…”

A coarse-grained xDLVO model for colloidal protein–protein interactions

“…68,69 These interactions are not included in the majority of solubility models (also not in (x)DLVO), however, Ninham and coworkers have demonstrated the importance of ion-macroion dispersion interactions in the PMF. [70][71][72] Including this effect leads to more accurate modeling [73][74][75][76] of the salt influence, modifying the dependence of B 22 on the ionic strength even for the monovalent ions of a similar size. Therefore, a new term to model the ion-protein dispersion potential was added to the total PMF in xDLVO-CG.…”

Theoretical analysis of excipient concentrations during the final ultrafiltration/diafiltration step of therapeutic antibody

“…[12][13][14][15][16][17][18][19][20][21][22][23][24] In a protein solution, the Poisson equation can describe the charge density of an aqueous solution using the electric potential of the charged protein molecules. 25,26 The Boltzmann distribution can describe the distribution of charged buffer molecules that are affected by the electrical potential generated by the proteins. Coupling these two equations together gives the Poisson-Boltzmann equation, which links the electrical potential distribution of excipients with the surface charge density of the charged protein molecules.…”