科研之友
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摘要
We review recent advances in the understanding of ejection mechanisms of solvated ions and charged macromolecules from highly charged nanodroplets. While the physical basis for the instability leading to droplet fragmentation is relatively well understood, a description of molecular mechanism of the fragmentation in complex systems is still missing. Development of a comprehensive model for the droplet fragmentation is further complicated by chemical modifications of the charged macromolecules (macroions) in a changing droplet environment. We highlight several different molecular simulation techniques used to study fragmentation of charged droplets with different solutes. Ejection of simple ions is analysed using theory of activated processes and transfer reaction coordinate (TRC). The TRC was shown to adequately represent complex rearrangement of solvent molecules in the course of evaporation. The critical value of the square of the charge to volume ratio for spontaneous ejection of simple solvated ions from aqueous droplets is found to be very close to that predicted by Rayleigh's model. On the contrary, the presence of macromolecules adds a level of complexity into the system where the charge-induced instabilities cannot be described by a conventional theory such as Rayleigh or ion-evaporation mechanism. Additional charge-charge interactions between charged sites on a macromolecule dramatically change the macroion ejection mechanism. Molecular dynamics simulations reveal a number of distinct scenarios: contiguous extrusion, drying-out, star-like formation of solvent surrounding a macroion and pearl formation along the macromolecular chain.
- 出版日期2015-2-11
