Positive ion nanoelectrospray mass spectra of cytochrome c formed from 100 mM ammonium bicarbonate, pH7, at (a) +0.75 kV spray potential (native) and (b) +1.3 kV spray potential (electrothermal supercharging), and from (c) a methanol/water/acetic acid solution (denaturing) at a spray potential of +0.80 kV. ETD of (d) the 7+ ion from native solution, (e) the 16+ ion from electrothermal supercharging from the same native solution, and (f) the 16+ ion from denaturing solution resulted in sequence coverages of 4%, 80%, and 80%, respectively.