Does Thermal Breathing Affect Collision Cross Sections of Gas-Phase Peptide Ions? An Ab Initio Molecular Dynamics Study

作者：Pepin Robert; Petrone Alessio; Laszlo Kenneth J; Bush Matthew F; Li Xiaosong; Turecek Frantisek^*

来源：Journal of Physical Chemistry Letters, 2016, 7(14): 2765-2771.

DOI：10.1021/acs.jpclett.6b01187

Ab initio molecular dynamics (AIMD) with density functional theory (DFT) was applied to explore conformational motions and collision cross sections (Omega) of folded (2) and extended (7) conformers of doubly charged peptide ions, (Ala-Ala-Leu-Arg + 2H)(2+), in the gas phase at 300 and 473 K. The experimental Omega, of (Ala-Ala-Leu-Arg + 2H)(2+) was measured as 149 +/- 1.2 angstrom(2) at 298 K. Thermally distributed mean values of Omega for 2 and 7 at 300 and 473 K were only 0.8-1.1% larger than for the equilibrium 0 K structures. Long (>10 ps) trajectory calculations indicated entropy-driven conformational change of 2 to 7 that occurred at random within a similar to 4 ps time The experimental Omega was found to fit the calculated population averaged values for 2 and 7, indicating a rapid conformer interconversion. Overall, thermal breathing had only a minor effect on the peptide ion collision cross sections.

• 出版日期2016-7-21