title: Electrokinetic characteristics of HSA dimer and its monolayers at mica.
abstract: Human serum albumin (HSA) dimer was synthesized in a reaction of the monomer with 1,6-bis(maleimido)hexane (BMH) cross-linker. Thorough physicochemical characteristics of the dimer were performed. They comprised the diffusion coefficient, hydrodynamic diameter, electrophoretic mobility as a function of pH, isoelectric point and electrokinetic charge. The adsorption of the dimer molecules at mica was studied using the atomic force microscopy (AFM) and in situ streaming potential measurements. The kinetics of adsorption was determined by a direct AFM imaging of single molecules over various substrate areas and interpreted in terms of the random sequential adsorption model. These results were consistent with streaming potential measurements carried out for the parallel-plate channel flow. It was also shown by these measurements that the desorption of the monomer under flow conditions was negligible. In this way, the amount of irreversibly bound dimer was quantitatively evaluated to be 0.5 mgm(-2) for ionic strength of 0.01 and pH 3.5 that is similar that to previous result obtained for the albumin monomer. This indicates that the dimer adsorption occurs mostly in the side-on orientation. Finally, the electrokinetic characteristics of the dimer monolayers on mica were performed by the streaming potential method. It was observed that for lower pHs the zeta potential of monolayers is much lower than the bulk zeta potential of the dimer molecules. This was attributed to a heterogeneous charge distribution. It was concluded that the well-characterized HSA dimer monolayers can be used for quantitatively determining ligand and drug binding that has an essential practical significance.
authors.affiliation: J. Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Niezapominajek 8, 30-239 Cracow, Poland. Electronic address: nckujda@cyf-kr.edu.pl.
authors.forename: Marta
authors.initials: M
authors.lastname: Kujda
authors.affiliation: J. Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Niezapominajek 8, 30-239 Cracow, Poland.
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Adamczyk
authors.affiliation: Faculty of Chemistry of the Jagiellonian University, Ingardena 3, 30-060 Cracow, Poland.
authors.forename: Szczepan
authors.initials: S
authors.lastname: Zapotoczny
authors.affiliation: Faculty of Biochemistry, Biophysics and Biotechnology of the Jagiellonian University, Gronostajowa 7, 30-387 Cracow, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Kowalska
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D019281:Dimerization; D006801:Humans; D007700:Kinetics; D018625:Microscopy, Atomic Force; D012709:Serum Albumin / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D012709:Serum Albumin; C011934:mica
keywords: AFM measurements of albumin dimer; Albumin dimer adsorption on mica; Monolayers of albumin dimer on mica; Physicochemical properties of albumin dimer; Streaming potential of albumin dimer adsorption; Zeta potential of albumin dimer covered mica