Hydrogen in N-methylacetamide: Positions and dynamics of the hydrogen atoms using neutron scattering

Heloisa N. Bordallo; Dimitri N. Argyriou; Mariette Barthès; Walter Kalceff; Stephane Rols; Kenneth W. Herwig; Carlos Fehr; Fanni Juranyi; Tilo Seydel

doi:10.1021/jp068528z

Hydrogen in N-methylacetamide: Positions and dynamics of the hydrogen atoms using neutron scattering

Heloisa N. Bordallo^*, Dimitri N. Argyriou, Mariette Barthès, Walter Kalceff, Stephane Rols, Kenneth W. Herwig, Carlos Fehr, Fanni Juranyi, Tilo Seydel

^*Corresponding author for this work

11 Citations (Scopus)

Abstract

This work reports neutron diffraction and incoherent neutron scattering experiments on N-methylacetamide (NMA), which can be considered the model building block for the peptide linkage of polypeptides and proteins. Using the neutron data, we have been able to associate the onset of a striking negative thermal expansion (NTE) along the α-axis with a dynamical transition around 230 K, consistent with our calorimetric experiments. Observation of the NTE raises the question of possible proton transfer in NMA, which, from our data alone, still cannot be settled. We can only speculate that intermolecular repulsive forces increase as the O⋯H distance decreases upon cooling, and that around 230 K the lattice relaxes without observation of an actual proton transfer. However, the existence of a nonharmonic potential, reflected by the behavior of the phonon vibrations together with the observation of NTE, could be justified by the "vibrational" polaron theory in which a dynamic localization of the vibrational energy is created by coupling an internal molecular mode to a lattice phonon. More generally, this work shows that neutron powder diffraction techniques can be very powerful for investigating structural deformations in small peptide systems.

Original language	English
Journal	Journal of Physical Chemistry B
Volume	111
Issue number	27
Pages (from-to)	7725-7734
Number of pages	10
ISSN	1520-6106
DOIs	https://doi.org/10.1021/jp068528z
Publication status	Published - 12 Jul 2007
Externally published	Yes

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title = "Hydrogen in N-methylacetamide: Positions and dynamics of the hydrogen atoms using neutron scattering",

abstract = "This work reports neutron diffraction and incoherent neutron scattering experiments on N-methylacetamide (NMA), which can be considered the model building block for the peptide linkage of polypeptides and proteins. Using the neutron data, we have been able to associate the onset of a striking negative thermal expansion (NTE) along the α-axis with a dynamical transition around 230 K, consistent with our calorimetric experiments. Observation of the NTE raises the question of possible proton transfer in NMA, which, from our data alone, still cannot be settled. We can only speculate that intermolecular repulsive forces increase as the O⋯H distance decreases upon cooling, and that around 230 K the lattice relaxes without observation of an actual proton transfer. However, the existence of a nonharmonic potential, reflected by the behavior of the phonon vibrations together with the observation of NTE, could be justified by the {"}vibrational{"} polaron theory in which a dynamic localization of the vibrational energy is created by coupling an internal molecular mode to a lattice phonon. More generally, this work shows that neutron powder diffraction techniques can be very powerful for investigating structural deformations in small peptide systems.",

author = "Bordallo, {Heloisa N.} and Argyriou, {Dimitri N.} and Mariette Barth{\`e}s and Walter Kalceff and Stephane Rols and Herwig, {Kenneth W.} and Carlos Fehr and Fanni Juranyi and Tilo Seydel",

year = "2007",

month = jul,

day = "12",

doi = "10.1021/jp068528z",

language = "English",

volume = "111",

pages = "7725--7734",

journal = "Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical",

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TY - JOUR

T1 - Hydrogen in N-methylacetamide

T2 - Positions and dynamics of the hydrogen atoms using neutron scattering

AU - Bordallo, Heloisa N.

AU - Argyriou, Dimitri N.

AU - Barthès, Mariette

AU - Kalceff, Walter

AU - Rols, Stephane

AU - Herwig, Kenneth W.

AU - Fehr, Carlos

AU - Juranyi, Fanni

AU - Seydel, Tilo

PY - 2007/7/12

Y1 - 2007/7/12

N2 - This work reports neutron diffraction and incoherent neutron scattering experiments on N-methylacetamide (NMA), which can be considered the model building block for the peptide linkage of polypeptides and proteins. Using the neutron data, we have been able to associate the onset of a striking negative thermal expansion (NTE) along the α-axis with a dynamical transition around 230 K, consistent with our calorimetric experiments. Observation of the NTE raises the question of possible proton transfer in NMA, which, from our data alone, still cannot be settled. We can only speculate that intermolecular repulsive forces increase as the O⋯H distance decreases upon cooling, and that around 230 K the lattice relaxes without observation of an actual proton transfer. However, the existence of a nonharmonic potential, reflected by the behavior of the phonon vibrations together with the observation of NTE, could be justified by the "vibrational" polaron theory in which a dynamic localization of the vibrational energy is created by coupling an internal molecular mode to a lattice phonon. More generally, this work shows that neutron powder diffraction techniques can be very powerful for investigating structural deformations in small peptide systems.

AB - This work reports neutron diffraction and incoherent neutron scattering experiments on N-methylacetamide (NMA), which can be considered the model building block for the peptide linkage of polypeptides and proteins. Using the neutron data, we have been able to associate the onset of a striking negative thermal expansion (NTE) along the α-axis with a dynamical transition around 230 K, consistent with our calorimetric experiments. Observation of the NTE raises the question of possible proton transfer in NMA, which, from our data alone, still cannot be settled. We can only speculate that intermolecular repulsive forces increase as the O⋯H distance decreases upon cooling, and that around 230 K the lattice relaxes without observation of an actual proton transfer. However, the existence of a nonharmonic potential, reflected by the behavior of the phonon vibrations together with the observation of NTE, could be justified by the "vibrational" polaron theory in which a dynamic localization of the vibrational energy is created by coupling an internal molecular mode to a lattice phonon. More generally, this work shows that neutron powder diffraction techniques can be very powerful for investigating structural deformations in small peptide systems.

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U2 - 10.1021/jp068528z

DO - 10.1021/jp068528z

M3 - Journal article

AN - SCOPUS:34547420851

SN - 1520-6106

VL - 111

SP - 7725

EP - 7734

JO - Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical

JF - Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical

IS - 27

ER -

Hydrogen in N-methylacetamide: Positions and dynamics of the hydrogen atoms using neutron scattering

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