Chemical Dynamics Simulations of Energy Transfer in Collisions of Protonated Peptide Ions with a Perfluorinated Alkylthiol Self-Assembled Monolayer Surface

摘要

Classical trajectory simulations are performed to study energy transfer in collisions of protonated diglycine, gly_(2)-H~(+), and dialanine, ala_(2)-H~(+), ions with a fluorinated alkanethiol self-assembled monolayer (F-SAM) surface on gold for a collision energy E_(i) in the range of 5-70 eV and incident angles i of (theta)_(i) and 45 deg with respect to the surface normal. Both explicit-atom (EA) and united-atom (UA) models were used to represent the F-SAM surface. The simulations show the distribution of energy transfer to vibrational/rotational degrees of freedom, (DELTA)E_(int), and to the surface, (DELTA)E_(surf), and of energy remaining in peptide ion translation, E_(f), are very similar for gly_(2)-H~(+), and ala_(2)-H~(+). The average percent energy transferred to (DELTA)E_(surf) and E_(f) increases and decreases, respectively, with increase in Ei. Average energy transfer to (DELTA)E_(int) is less dependent on E_(i). Changing (theta)_(i) from 0 to 45, (DELTA)E_(int) shows the least sensitive relative to (DELTA)E_(surf) and E_(f). The effect of masses is studied to explain why the energy transfer efficiencies in F-SAM are two times larger than that in hydrocarbon SAM surface (H-SAM). The EA and UA models both give reasonable energy transfer distributions compared with experiment, although there are some differences.