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Updated: May 9, 2026

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050
Published on: May 13, 2020
Molecular flexibility and structural instabilities in crystalline l-methionine
Jennifer Fischer1, José A Lima, Paulo T C Freire
1Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany; Helmholtz Zentrum Berlin für Materialien und Energie, Hahn Meitner Platz 1, 14109 Berlin, Germany.
Crystalline l-methionine exhibits dynamic disorder above 275K, linked to its flexible thiol-ether group. This structural transition involves changes in lattice parameters and molecular motions, studied via neutron scattering and X-ray diffraction.
Area of Science:
- Solid-state physics
- Materials science
- Crystallography
Background:
- l-Methionine is a sulfur-containing amino acid.
- Previous studies noted anomalies in specific heat measurements around 307K.
Purpose of the Study:
- Investigate the dynamics of polycrystalline l-methionine.
- Characterize the structural transition occurring at approximately 307K.
Main Methods:
- Incoherent inelastic and quasielastic neutron scattering.
- X-ray powder diffraction.
- Ab-initio calculations.
Main Results:
- Observed an anomalous drop in the c-lattice parameter and a change in the β-monoclinic angle at ~190K.
- Identified onset and slowing of CH3-S group reorientational motions above 130K.
- Detected large-amplitude motions and damping of vibrations above 275K, indicating dynamic disorder.
Conclusions:
- The crystalline structure of l-methionine is dynamically disordered above 275K.
- This disorder is attributed to the flexibility of the molecular thiol-ether group.
- Results correlate structural dynamics with observed thermal anomalies.
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