Mechanism of Protein Electrospray Ionization Explored by Molecular Dynamics Simulations

摘要

The ns time scale of our simulations is not long enough to observe separation of a protein from the water droplet in any of the cases studied here. Insights into the ESI mechanism can nonetheless be obtained. The initial droplets are highly unstable (close to the Rayleigh limit). Electrostatic stress can be relieved in two ways: (1) Ejection of solvated charge carriers. This is the preferred scenario for proteins that are hydrophilic and/or folded (Figs. 2, 4, 5). Release of the protein into the gas phase will occur very slowly, likely following a CRM scenario. Low protein ESI efficiency. (2) Protein ejection. This is the case for proteins that are unfolded and hydrophobic. Release of the protein into the gas phase shows certain IEM-like features, reminiscent of the ejection of small ions from mixed organic/aqueous droplets [2]. High protein ESI efficiency (Fig. 3).