Figure 3.

The crosslinking reaction progress was assessed using (a) Fluorescence intensity test by tracking the fluorescence intensity of blue fluorescent pigmentation generated by Genipin reaction with primary amines in peptides at 630 nm at different time points, (b) Ninhydrin assay by measuring the loss of free amine groups, reacted with ninhydrin, based on optical absorbance measurements at 570 nm, and (c) FTIR analysis to delineate the chemical and secondary structure changes in peptides after crosslinking by Genipin. The spectra were averaged and processed with the OriginPro software using Boltzmann fitting and York linear fitting.