The Vroman Effect:  A Molecular Level Description of Fibrinogen Displacement

Abstract

The molecular level details of the displacement of surface adsorbed fibrinogen from silica substrates were studied by atomic force microscopy, immunochemical assays, fluorescence microscopy, and vibrational sum frequency spectroscopy. The results showed that human plasma fibrinogen (HPF) can be readily displaced from the interface by other plasma proteins near neutral pH because the positively charged alpha C domains on HPF sit between the rest of the macromolecule and the underlying surface. The alpha C domains make weak electrostatic contact with the substrate, which is manifest by a high degree of alignment of Lys and Arg residues. Upon cycling through acidic pH, however, the alpha C domains are irreversibly removed from this position and the rest of the macromolecule is free to engage in stronger hydrogen bonding, van der Waals, and hydrophobic interactions with the surface. This results in a 170-fold decrease in the rate at which HPF can be displaced from the interface by other proteins in human plasma.

Protein Adsorption on Nano-scaled, Rippled TiO2 and Si Surfaces

“…On non-irradiated and irradiated flat Si we observed mostly globularly adsorbed proteins with small amount of HPF networks (see supplementary information). The latter probably originates from some proteins that adsorb in a stretched conformation, which is well in agreement with the hydrophilic character of the SiO 2 layer on top of Si [19]. Figure 4a shows an AFM height picture of TiO 2 with a ripple wavelength of k = 125 nm after the adsorption process.…”

“…Surface-bonded HPF has a length of 46-49 nm and a height about 0.3-2.5 nm depending on the protein conformation on different substrates and under different environmental conditions [7,[10][11][12][13]. Former studies mostly investigated the adsorption of HPF and a variety of other proteins [14,15] on flat substrates such as commercially pure Ti with a natural TiO 2 layer on top [13], TiO 2 [7], graphite [10,11,16], mica [10,12,13], ultra-high molecular weight polyethylene [17], Si [18] or SiO 2 [19]. In most cases, these investigations concentrated on the adsorption of single proteins in air and/or under aqueous conditions.…”

A Comprehensive Mechanism of Fibrin Network Formation Involving Early Branching and Delayed Single- to Double-Strand Transition from Coupled Time-Resolved X-ray/Light-Scattering Detection

“…21,22 Further work with recombinant FG species with missing 48 or human/chicken hybrid 49 αC regions, and with either uncleavable FpB's or nonbinding B knobs/ unavailable b holes and thrombin as the enzyme, is planned. It should help to clarify the role played by the largely unstructured Aα chain appendages, which are also functionally important for FG adhesion, 50,51 …”

Theory, fabrication and applications of microfluidic and nanofluidic biosensors

“…The device used to perform this study is shown in figure 8. Another method of dealing with the non-specific binding of proteins exploits the Vroman effect [171,172]. The Vroman effect is when a weak affinity protein bound to the surface of a substrate is displaced by a strong affinity protein.…”