Increase in the Transition Enthalpy of Fibrinogen upon Adsorption onto Hydroxyapatite

The increase of the protein transition enthalpy upon adsorption onto biomedical material surfaces was observed by measuring the differential scanning calorimetry (DSC) traces of bovine fibrinogen adsorbed onto a hydroxyapatite surface. The mechanism causing the transition enthalpy increase upon adsorption Was clarified by using DSC measurements of bovine fibrinogen for different ionic strength and sodium dodecyl sulfate concentrations. The results suggest that the increased fibrinogen transition enthalpy may be attributed to the electrostatic interactions between the carboxyl of the D domains and the calcium loci of hydroxyapatite, which may result in a more compact protein structure.