The extra-cellular matrix protein, amelogenin, has been studied for its adsorption to a hydroxyapatite (HAP) surface/solution interface, acting as a surrogate for enamel mineral, using quartz crystal microbalance (QCM). Dynamic flow-based experiments were conducted to evaluate the effect of solution pH and phosphorylation state of the amelogenin protein. Loading capacities and adsorption affinities (Kad) were calculated when Langmuir isotherm conditions appeared to be met. At pH 8.0, binding was remarkably similar for the two proteins, but at pH 7.4 a higher affinity and lower surface loading for the phosphorylated protein was found. This suggests that phosphorylated amelogenin adopts a more extended conformation than non-phosphorylated full-length amelogenin, occupying a larger footprint on the HAP surface. This surface-induced structural difference may help explain why the phosphorylated protein is a more effective inhibitor of spontaneous mineral formation in vitro than the non-phosphorylated version. These collective findings provide new insight into the important role of amelogenin phosphorylation in the mechanism by which amelogenin regulates enamel crystal formation.

Dynamic interactions of amelogenin with hydroxyapatite surfaces are dependent on protein phosphorylation and solution pH

253rd National Meeting (2017)

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