title: Revealing fibrinogen monolayer conformations at different pHs: electrokinetic and colloid deposition studies.
abstract: Adsorption mechanism of human fibrinogen on mica at different pHs is studied using the streaming potential and colloid deposition measurements. The fibrinogen monolayers are produced by a controlled adsorption under diffusion transport at pH of 3.5 and 7.4. Initially, the electrokinetic properties of these monolayers and their stability for various ionic strength are determined. It is shown that at pH 3.5 fibrinogen adsorbs irreversibly on mica for ionic strength range of 4×10(-4) to 0.15 M. At pH 7.4, a partial desorption is observed for ionic strength below 10(-2) M. This is attributed to the desorption of the end-on oriented molecules whereas the side-on adsorbed molecules remain irreversibly bound at all ionic strengths. The orientation of molecules and monolayer structure is evaluated by the colloid deposition measurements involving negatively charged polystyrene latex microspheres, 820 nm in diameter. An anomalous deposition of negative latex particles on substrates exhibiting a negative zeta potential is observed. At pH 3.5 measurable deposition of latex is observed even at low ionic strength where the approach distance of latex particles exceeded 70 nm. At pH 7.4 this critical distance is 23 nm. This confirms that fibrinogen monolayers formed at both pHs are characterized by the presence of the side-on and end-on oriented molecules that prevail at higher coverage range. It is also shown that positive charge is located at the end parts of the αA chains of the adsorbed fibrinogen molecules. Therefore, it is concluded that the colloid deposition method is an efficient tool for revealing protein adsorption mechanisms at solid/electrolyte interfaces.
authors.affiliation: J. Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Niezapominajek 8, 30-239 Cracow, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Nattich-Rak
authors.affiliation: J. Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Niezapominajek 8, 30-239 Cracow, Poland. Electronic address: ncadamcz@cyf-kr.edu.pl.
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Adamczyk
authors.affiliation: J. Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Niezapominajek 8, 30-239 Cracow, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Wasilewska
authors.affiliation: J. Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Niezapominajek 8, 30-239 Cracow, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Sadowska
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry; D003102:Colloids / Q000737:chemistry; D005340:Fibrinogen / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D011487:Protein Conformation; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; D003102:Colloids; D005340:Fibrinogen; C011934:mica
keywords: Colloid particle deposition; DLVO theory; Fibrinogen monolayers on mica; Heterogeneous surface deposition; Latex particle deposition; Streaming potential of fibrinogen monolayers; Zeta potential of fibrinogen covered mica