The Binding of Human Serum Albumin by Monodisperse Polystyrene Latex Particles

Abstract

The binding of human serum albumin by monodisperse latex particles was studied applying the radioisotope labelling technique. The radiochemically active substance was 1311-labelled albumin and the latices were monodisperse samples ranging in particle size from 200 to 940 nm. All experiments were performed in buffered solutions at pH 8.0 and the ionic strength 0.05. I n one type of binding experiments human serum albumin was added in great excess leading to a saturation of latex particle surface. The excess albumin was removed by centrifugation and washing of the sediments by pure buffer. For two latex samples the binding isotherms were determined. The results of the experiments with excess albumin suggest that a nearly constant amount is bound per unit particle surface irrespective of the latex sample and particle size. One washing was shown t o take away approximately some loo/, of bound albumin from the particle surface demonstrating fairly strong binding. From the binding isotherms the binding constants K and the standard free energies of binding AGO were estimated. Values of K about 6 pM-l and AGO about -9 kcal/mol indicate high affinity of human serum albumin to the latex particle surface. The results of the present experiments are discussed from the point of view of recent findings on protein interactions with detergent molecules. The results indicate a possible expansion of the tertiary structure of the human serum albumin molecule in its part attached to the particle surface whereas the part of the molecule oriented to the solution remains in its native conformation as is seen from the preserved immunochemical activity against specific antibodies.

The feasibility of radiolabeling for human serum albumin (HSA) adsorption studies

“…[7] (ii) The adsorption of either A or B is irreversible. In this case the surface will be covered completely by the molecules which adsorb irreversibly.…”

“…[7] and [10], this expression for experiments with depletion in solution is related to the preferential adsorption factor 4) without depletion:…”

“…These are depletion techniques (5-10), spectroscopic techniques, such as colorimetry (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13), ATR/ IR (14)(15)(16)(17), CD (18), and ellipsometry (19)(20)(21)(22)(23)(24)(25), and radio labeling (7,(26)(27)(28). This last method seems to be a very elegant one, which offers the possibility of determining the simultaneous adsorption of different proteins onto a surface.…”

Latex agglutination tests for selected Escherichia coli enzymes

“…It is well known that detergents decrease or inhibit the binding of proteins to polymeric surfaces (69,103,271,306,323). With current polymerization processes used by many latex manufacturers, removal of the emulsifier is necessary to obtain a well-characterized surface for protein binding.…”

“…The diameter of a latex particle determines total surface area available for adsorbing ligands (23,47,69,231,271,272). The amount of any proteinaceous ligand adsorbed is proportional to the diameter of the latex.…”