Figure 2. Native MS spectra of the OCP. (A) The dark-adapted (sample colored orange) OCP in 200 mM ammonium acetate was analyzed by
native MS. Two charge envelopes were observed in the spectrum. The left envelope (labeled in red) corresponds to the MW of the monomeric OCP
and one 3′-hECN. The right envelope (labeled in orange) corresponds to the MW of the dimeric OCP and two 3′-hECNs. The dark-adapted sample
was illuminated with white light for 1.5 min. Two spectra were acquired when the OCP sample was restored to a dark environment for 5 and 30 min.
(B) Native MS of the OCP with a collision energy ramp. (C) Two-dimensional IM-MS spectrum of the OCP sample. The Y axis shows the mass
spectrometry measurement (mass to charge ratio, m/z), while the X axis shows the ion mobility measurement (drift time, milliseconds). Multiple
charge states from two species were grouped into monomer (red) and dimer (orange). (D) Ion mobility measurement of the OCP. Two charge
states, one for the OCP monomer (+11) and one for the OCP dimer (+16), were monitored by ion mobility with the collision energy ramp.