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Title: | Adsorption of flexible proteins in the 'wrong side' of the isoelectric point: Casein macropeptide as a model system |
Author: | Blanco Andrés, Pablo M. Achetoni, Micaela M. Garcés, Josep Lluís Madurga Díez, Sergio Mas i Pujadas, Francesc Baieli, María F. Narambuena, Claudio F. F. |
Keywords: | Caseïna Adsorció Pèptids Casein Adsorption Peptides |
Issue Date: | 10-Jun-2022 |
Publisher: | Elsevier B.V. |
Abstract: | We analyze the conditions of the adsorption of a flexible peptide onto a charged substrate in the 'wrong side' of the isoelectric point (WSIP), i.e. when surface and peptide charges have the same sign. As a model system, we focus on the casein macropeptide (CMP), both in the aglycosylated (aCMP) and fully glycosydated (gCMP) forms. We model the substrate as a uniformly charged plane while CMP is treated as a bead-and-spring model including electrostatic interactions, excluded volume effects and acid/base equilibria. Adsorption coverage, aminoacid charges and concentration profiles are computed by means of Monte Carlo simulations at fixed pH and salt concentration. We conclude that for different reasons the CMP can be adsorbed to both positively and negatively charged surfaces in the WSIP. For negatively charged surfaces, WSIP adsorption is due to the patchy distribution of charges: the peptide is attached to the surface by the positively charged end of the chain, while the repulsion of the surface for the negatively charged tail is screened by the small ions of the added salt. This effect increases with salt concentration. Conversely, a positively charged substrate induces strong charge regulation of the peptide: the acidic groups are deprotonated, and the peptide becomes negatively charged. This effect is stronger at low salt concentrations and it is more intense for gCMP than for aCMP, due to the presence of the additional sialic groups in gCMP. |
Note: | Versió postprint del document publicat a: https://doi.org/10.1016/j.colsurfb.2022.112617 |
It is part of: | Colloids and Surfaces B-Biointerfaces, 2022, vol. 217, p. 112617 |
URI: | http://hdl.handle.net/2445/189572 |
Related resource: | https://doi.org/10.1016/j.colsurfb.2022.112617 |
ISSN: | 0927-7765 |
Appears in Collections: | Articles publicats en revistes (Institut de Química Teòrica i Computacional (IQTCUB)) Articles publicats en revistes (Ciència dels Materials i Química Física) |
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