Figure 1.

a) Extracted ion chromatograms (EIC) for unmodified (black), BHD-modified (light blue) and d₅-BHD modified (dark blue) cyclo(RGDFE), product-ion (MS/MS) spectrum for BHD- b) and d₅-BHD- c) modified cyclo(RGDFE). (Orange circle: loss of NH₃, blue circle: loss of H₂O, yellow square: addition 118.0524 or 123.0845 mass unit, green square: addition of 118.0524 or 123.0845 mass unit and loss of H₂O, pink square: addition of 118.0524 or 123.0845 mass unit and loss of NH₃.) $Modification extent=\frac{\sum I_{modified}}{\sum I_{modified}+\sum I_{unmodified}}$(The nomenclature for cyclic peptides is that by Ngoka and Gross³⁹, figure itself is original. Details are shown in Scheme S1.)