Representative native-MS spectra acquired under optimized instrument conditions for bacteriorhodopsin (B-0184) on the: a) Q-ToF (source block temperature 30°C, sample cone 25 V, TWIG trap 100 V); b) Orbitrap (capillary temperature 200°C, source induced dissociation 20 V, HCD 100 V); c) FT-ICR (capillary temp 100°C, skimmer 25 V, collision cell 40 V). The effect of bacteriorhodopsin (B-0184) charge-state liberation (z = 9+) by source and collisional activation, as a function of source temperature on the: d) Q-ToF; e) Orbitrap; f) FT-ICR. The respective collision (or HCD) cell gases are: Q-ToF, SF6; Orbitrap, N2 and FT-ICR, Ar. SID refers to source induced dissociation; CID refers to collision induced dissociation. n=1.