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

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• 作者：Robert Pepin ; Alessio Petrone ; Kenneth J. Laszlo ; Matthew F. Bush ; Xiaosong Li ; František Tureček
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2016
• 出版时间：July 21, 2016
• 年：2016
• 卷：7
• 期：14
• 页码：2765-2771
• 全文大小：425K
• 年卷期：0
• ISSN：1948-7185

文摘

Ab initio molecular dynamics (AIMD) with density functional theory (DFT) was applied to explore conformational motions and collision cross sections (Ω) 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 Ω of (Ala–Ala–Leu–Arg +2H)²⁺ was measured as 149 ± 1.2 Ų at 298 K. Thermally distributed mean values of Ω 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 ∼ 4 ps time window. The experimental Ω 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.