Hypothetical drawing of the process of nanoelectrospraying proteins into the gas phase (right) and its implications on the protein free-energy landscape (left). In solution, rapid interconversion of protein structures [native (N), intermediate (I), denatured (D)] is mediated by solvent. During early states of n-ESI, the droplet initiates with solution populations in equilibrium with rapidly exchanging protons (bottom). As the droplet dries, the solution equilibrium is quenched due to evaporative cooling (middle). Just before entering the MS instrument, protein structures are kinetically trapped on a new, gas-phase free energy landscape associated with the solvent-free ion (top).