Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/91194
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Type: Journal article
Title: Liquid hot NAGMA cooled to 0.4 K: Benchmark thermochemistry of a gas-phase peptide
Author: Leavitt, C.
Moore, K.
Raston, P.
Agarwal, J.
Moody, G.
Shirley, C.
Schaefer, H.
Douberly, G.
Citation: Journal of Physical Chemistry A, 2014; 118(41):9692-9700
Publisher: American Chemical Society
Issue Date: 2014
ISSN: 1089-5639
1520-5215
Statement of
Responsibility: 
Christopher M. Leavitt, Kevin B. Moore III, Paul L. Raston, Jay Agarwal, Grant H. Moody, Caitlyne C. Shirley, Henry F. Schaefer III, and Gary E. Douberly
Abstract: Vibrational spectroscopy and helium nanodroplet isolation are used to determine the gas-phase thermochemistry for isomerization between conformations of the model dipeptide, N-acetylglycine methylamide (NAGMA). A two-stage oven source is implemented to produce a gas-phase equilibrium distribution of NAGMA conformers, which is preserved when individual molecules are captured and cooled to 0.4 K by He nanodroplets. With polarization spectroscopy, the IR spectrum in the NH stretch region is assigned to a mixture of two conformers having intramolecular hydrogen bonds composed of either five- or seven-membered rings, C5 and C7, respectively. The C5 to C7 interconversion enthalpy and entropy, obtained from a van't Hoff analysis, are -4.52 ± 0.12 kJ/mol and -12.4 ± 0.2 J/(mol · K), respectively. The experimental thermochemistry is compared to high-level electronic structure theory computations.
Keywords: Helium; Gases; Peptides; Spectrum Analysis; Hydrogen Bonding; Nanotechnology; Vibration; Thermodynamics; Entropy; Models, Molecular
Rights: © 2014 American Chemical Society
RMID: 0030018879
DOI: 10.1021/jp5092653
Appears in Collections:Physics publications

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