Conference paper

The Role of Charged Groups in the Adsorption of Proteins at Solid Surfaces

Willem Norde ; Laboratory for Physical and Coloid Chemistry of the Agricultural University De Dreijen 6, 6703 BC Wageningen, The Netherlands

Abstract

Interaction between electric charges is an important factor in
protein adsorption. Similar charge signs on the protein and the
sorbent surface opposes adsorption, but whether it prevents ad.:
sorption depends on other factors such as dehydration of the
protein and the sorbent and structural rearrangements in the
protein molecule. Ribonuclease, that does not strongly change its
structure upon adsorption, adsorbs on hydrophilic surfaces only
if its charge sign is opposite that of the sorbent. On increasing the
hydrophobicity of the sorbent adsorption also takes place in the
case of the same charge sign. Blood plasma albumin, on the other
hand, adsorbs at any interface even if the sorbent is h ydrophilic
and has the same charge sign as the protein. In this case the
driving force for adsorption stems from dehydration and/or conformational
changes in the protein molecule. Although a same
charge sign may not prevent adsorption to occur, it may slow
down the adsorption process. This has been demonstrated for
albumin at negatively charged polystyrene surfaces. The Gibbs
free energy of the net electrostatic interaction is relatively insensitive
for the charge on the protein and the sorbent. This is due
to the role of small ions in the system: ions are eventually transferred
from the aqueous solution into the contact region between
the protein and the sorbent in order to prevent the development
of high electrostatic potentials in this region. The chemical effect
of the medium change of these ions is unfavorable and, since it is
proportional to the number of trasferred ions, it increases with
decreasing charge contrast between the protein and the sorbent
surface.

Keywords

Hrčak ID:

194192

URI

https://hrcak.srce.hr/194192

Publication date:

9.11.1983.

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