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. Author manuscript; available in PMC: 2014 Dec 17.
Published in final edited form as: Anal Chem. 2013 Nov 22;85(24):11966–11972. doi: 10.1021/ac402906d

Figure 2.

Figure 2

Reactive liquid sample DESI-MS spectra of RNaseA (5 μM in 20 mM NH4OAc aqueous solution, pH 6.5) in the sample transfer capillary (designated as “S” in the figure) with the DESI probe (designated as “D” in the figure) spraying reagents containing (a) 50 μM 2′-CMP; (b) 50 μM CDP; (c) 50 μM CTP in 20 mM NH4OAc. (d) Reactive DESI-MS spectrum of CTP (50 μM in 20 mM NH4OAc aqueous solution) in the sample transfer capillary (“S“) with the DESI probe (“D”) spraying 5 μM RNaseA (20 mM NH4OAc). Unfilled circles represent free protein ions (apo) and solid circles represent protein-ligand complex ions (holo).