TY - JOUR
T1 - An Isosymmetric High-Pressure Phase Transition in α-Glycylglycine
T2 - A Combined Experimental and Theoretical Study
AU - Clarke, Samantha M.
AU - Steele, Brad A.
AU - Kroonblawd, Matthew P.
AU - Zhang, Dongzhou
AU - Kuo, I. Feng W.
AU - Stavrou, Elissaios
N1 - Publisher Copyright:
Copyright © 2019 American Chemical Society.
PY - 2020/1/9
Y1 - 2020/1/9
N2 - We investigated the effects of hydrostatic pressure on α-glycylglycine (α-digly) using a combined experimental and theoretical approach. The results of powder X-ray diffraction show a change in compressibility of the axes above 6.7 GPa, but also indicate that the structure remains in the same monoclinic space group, suggesting an isosymmetric phase transition. A noticeable change in the Raman spectra between 6 and 7.5 GPa further supports the observed phase transition. First-principles-based calculations combined with the crystal structure prediction code USPEX predict a number of possible polymorphs at high pressure. An orthorhombic structure with a bent peptide backbone is the lowest enthalpy polymorph above 6.4 GPa; however, it is not consistent with experimental observations. A second monoclinic structure isosymmetric to α-digly, α′-digly, is predicted to become more stable above 11.4 GPa. The partial atomic charges in α′-digly differ from α-digly, and the molecule is bent, possibly indicating different reactivity of α′-digly. The similarity in the lattice parameters predicted from calculations and the axial changes observed experimentally support that the α′-digly phase is likely observed at high pressure. A possible explanation for the isosymmetric phase transition is discussed in terms of relaxing strained hydrogen bonding interactions. Such combined experimental and modeling efforts provide atomic-level insight into how pressure-driven conformational changes alter hydrogen-bonding networks in complicated molecular crystals.
AB - We investigated the effects of hydrostatic pressure on α-glycylglycine (α-digly) using a combined experimental and theoretical approach. The results of powder X-ray diffraction show a change in compressibility of the axes above 6.7 GPa, but also indicate that the structure remains in the same monoclinic space group, suggesting an isosymmetric phase transition. A noticeable change in the Raman spectra between 6 and 7.5 GPa further supports the observed phase transition. First-principles-based calculations combined with the crystal structure prediction code USPEX predict a number of possible polymorphs at high pressure. An orthorhombic structure with a bent peptide backbone is the lowest enthalpy polymorph above 6.4 GPa; however, it is not consistent with experimental observations. A second monoclinic structure isosymmetric to α-digly, α′-digly, is predicted to become more stable above 11.4 GPa. The partial atomic charges in α′-digly differ from α-digly, and the molecule is bent, possibly indicating different reactivity of α′-digly. The similarity in the lattice parameters predicted from calculations and the axial changes observed experimentally support that the α′-digly phase is likely observed at high pressure. A possible explanation for the isosymmetric phase transition is discussed in terms of relaxing strained hydrogen bonding interactions. Such combined experimental and modeling efforts provide atomic-level insight into how pressure-driven conformational changes alter hydrogen-bonding networks in complicated molecular crystals.
UR - http://www.scopus.com/inward/record.url?scp=85077058357&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcb.9b07313
DO - 10.1021/acs.jpcb.9b07313
M3 - 文章
C2 - 31794209
AN - SCOPUS:85077058357
SN - 1520-6106
VL - 124
SP - 1
EP - 10
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 1
ER -