Synthesis and characterization of collagen furan. Furan group was installed onto collagen through functionalization of the pendant amines from lysine and arginine side chains by reaction with furfuryl glycidyl ether (Figure ). The pKa of these amines is 10.5 and therefore, the reaction was performed at pH 10 to ensure the deprotonated state of the amine for a nucleophilic ring opening reaction. Protein modification through pendant amines by reacting with glycidyl moieties is well-established. The resulting collagen furan (CF) was analyzed by H NMR spectroscopy and the appearance of peaks at 6.38, 6.41 and 7.46 δ ppm was attributed to the aromatic protons of the furan group (Figure ). The degree of modification was determined by TNBS colorimetric assay and was found to be 61.4%±1.8% with respect to the amines in collagen.