The Rate of Protein Binding to Surfaces

When we coat surfaces or particles with proteins we often wonder, ‘how long until the coating is done? ‘ In this 2009 paper we addressed the question directly. We soaked 100 nm polystyrene particles in 10% serum (about 6 mg/ml protein) for different periods of time, washed the particles to remove unbound protein, soluablized the bound protein by suspending the particles in sample buffer, displayed the protein samples on SDS PAGE, stained the gel and quantified. Here is what we found …

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The overshoot is real as we saw it every time and found some explanation in the literature. In short the early phase is dominated by the fast on rate. The slower off rate comes on-line later and lowers the binding level at equilibrium. The fact that these dynamics are seen is evidence that there is at least some fraction of protein that experiences reversible binding to the surface.

The take home is that the binding is fast (mostly done in 10 minutes) and seems to reach equilibrium in about 30 minutes. Different surfaces and different proteins will give slightly different results. Incubating for an hour seems like a good rule of thumb.

 

About

Professor McGrath holds a BS degree in Mechanical Engineering from Arizona State and a MS degree in Mechanical Engineering from MIT. He earned a PhD in Biological Engineering from Harvard/MIT's Division of Health Sciences and Technology. He then trained as a Distinguished Post-doctoral Fellow in the Department of Biomedical Engineering at the Johns Hopkins University. Professor McGrath has been on the Biomedical Engineering faculty at the University of Rochester since 2001 where he also serves as the director of the graduate program BME and associate director of the URNano microfab and metrology core. McGrath's research was focused on the phenomena of cell migration until 2007 when he founded the interdisciplinary Nanomembrane Research Group to development and apply silicon membrane technologies. Professor McGrath is also a co-founder and past president of SiMPore Inc., a company founded to commercially manufacture silicon membranes and related technologies.

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