Structural isotopic effects in the smallest chiral amino acid: observation of a structural phase transition in fully deuterated alanine.
A first study of possible changes instigated by deuteration in amino acids was carried out using neutron diffraction, inelastic neutron scattering, and Raman scattering in l-alanine, C2H4(NH2)COOH. Careful analysis of the structural parameters shows that deuteration of l-alanine engenders significant geometric changes as a function of temperature, which can be directly related to the observation of new lattice vibration modes in the Raman spectra. The combination of the experimental data suggests that C2D4(ND2)COOD undergoes a structural phase transition (or a structural rearrangement) at about 170 K. Considering that this particular amino acid is a hydrogen-bonded system with short hydrogen bonds (O...H approximately 1.8 A), we evoke the Ubbelohde effect to conclude that substitution of hydrogen for deuterium gives rise to changes in the hydrogen-bonding interactions. The structural differences suggest distinct relative stabilities for the hydrogenous and deuterated l-alanine.
de Souza
Joelma M
JM
Freire
Paulo T C
PT
Bordallo
Heloisa N
HN
Argyriou
Dimitri N
DN
D000409:Alanine / Q000737:chemistry*; D003903:Deuterium; D015394:Molecular Structure; D033363:Neutron Diffraction; D044367:Phase Transition; D013059:Spectrum Analysis, Raman
D003903:Deuterium; D000409:Alanine