Structural Isotopic Effects in the Smallest Chiral Amino Acid: Observation of a Structural Phase Transition in Fully Deuterated Alanine

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• 作者：Joelma M. de Souza ; Paulo T.C. Freire ; Heloisa N. Bordallo ; Dimitri N. Argyriou
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：May 17, 2007
• 年：2007
• 卷：111
• 期：19
• 页码：5034 - 5039
• 全文大小：233K
• 年卷期：v.111,no.19(May 17, 2007)
• ISSN：1520-5207

文摘

A first study of possible changes instigated by deuteration in amino acids was carried out using neutrondiffraction, inelastic neutron scattering, and Raman scattering in L-alanine, C₂H₄(NH₂)COOH. Careful analysisof the structural parameters shows that deuteration of L-alanine engenders significant geometric changes asa function of temperature, which can be directly related to the observation of new lattice vibration modes inthe Raman spectra. The combination of the experimental data suggests that C₂D₄(ND₂)COOD undergoes astructural phase transition (or a structural rearrangement) at about 170 K. Considering that this particularamino acid is a hydrogen-bonded system with short hydrogen bonds (O···H ~ 1.8 Å), we evoke the Ubbelohdeeffect to conclude that substitution of hydrogen for deuterium gives rise to changes in the hydrogen-bondinginteractions. The structural differences suggest distinct relative stabilities for the hydrogenous and deuteratedL-alanine.