Figure 6. Solid-state NMR characterization of the RGD domain dynamics of the N15 fusion peptide on HAP. ¹³C CPMAS spectra were collected on a Chemagnetics CMX Infinity spectrometer operating at a ¹³C frequency of 125.72 MHz using a Chemagnetics doubly-resonant MAS probe. These experiments used a ¹H 90° pulsewidth of 7.5 msec followed by a contact time of 1.5 msec and a spinning speed of 3003 Hz. The surface-adsorbed samples were signal-averaged for 10,240 scans. The C-terminal glycine retained the large-amplitude dynamics typical of the N15 C-terminus, suggesting that the aspartic acid is not strongly interacting with the HAP surface. The RGD domain dynamics at this position may underlie the excellent cell-binding activity of this peptide when immobilized on HAP surfaces.