title: Molecular dynamics investigation of desorption and ion separation following picosecond infrared laser (PIRL) ablation of an ionic aqueous protein solution.
abstract: Molecular dynamics simulations were performed to characterize the ablation process induced by a picosecond infrared laser (PIRL) operating in the regime of desorption by impulsive vibrational excitation (DIVE) of a model peptide (lysozyme)/counter-ion system in aqueous solution. The simulations were performed for ablation under typical experimental conditions found within a time-of-flight mass spectrometer (TOF-MS), that is in vacuum with an applied electric field (E = ± 107V/m), for up to 2 ns post-ablation and compared to the standard PIRL-DIVE ablation condition (E = 0 V/m). Further, a simulation of ablation under an extreme field condition (E = 1010V/m) was performed for comparison to extend the effective dynamic range of the effect of the field on charge separation. The results show that the plume dynamics were retained under a typical TOF-MS condition within the first 1 ns of ablation. Efficient desorption was observed with more than 90% of water molecules interacting with lysozyme stripped off within 1 ns post-ablation. The processes of ablation and desolvation of analytes were shown to be independent of the applied electric field and thus decoupled from the ion separation process. Unlike under the extreme field conditions, the electric field inside a typical TOF-MS was shown to modify the ions' motion over a longer time and in a soft manner with no enhancement to fragmentation observed as compared to the standard PIRL-DIVE. The study indicates that the PIRL-DIVE ablation mechanism could be used as a new, intrinsically versatile, and highly sensitive ion source for quantitative mass spectrometry.
authors.affiliation: Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Zou
authors.affiliation: Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904-4745, USA.
authors.forename: C
authors.initials: C
authors.lastname: Wu
authors.affiliation: Max Plank Institute for the Structure and Dynamics of Matter, 149 Luruper Chaussee, 27761 Hamburg, Germany.
authors.forename: W D
authors.initials: WD
authors.lastname: Robertson
authors.affiliation: Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904-4745, USA.
authors.forename: L V
authors.initials: LV
authors.lastname: Zhigilei
authors.affiliation: Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: R J D
authors.initials: RJ
authors.lastname: Miller
mesh_terms: D004560:Electricity; D007259:Infrared Rays; D007834:Lasers; D056004:Molecular Dynamics Simulation; D009113:Muramidase / Q000737:chemistry*; D011487:Protein Conformation; D012996:Solutions; D014867:Water / Q000737:chemistry*
chemical_list: D012996:Solutions; D014867:Water; D009113:Muramidase