Proteins are amphoteric, that is, they possess a number of acid/base sites whose charge is pH dependent. Since a positively (negatively) charged surface will repel solvated protons (hydroxide ions) and thus raise (lower) the pH near to the surface, the sign of a protein's overall change could change upon approach to the surface. In this case, attraction that is indeed electrostatic in origin may follow. Could this effect explain the antielectrostatic behavior reported in the literature? Evidence to suggest otherwise lies in the following observation: the degree of buffering has been shown to have little effect on these antielectrostatic adsorption trends (Brusatori and Van Tassel 2003).
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