Pressure Effects on Columnar Lyotropics:  Anisotropic Compressibilities in Guanosine Monophosphate Four-Stranded Helices

Abstract

Guanosine in water self-associates into stable structures, made by four-stranded helices composed of stacked guanosine tetramers. High-pressure synchrotron X-ray diffraction was used to investigate helix stability and energetics in the hexagonal phase. An unusual lateral interhelix negative compressibility was found, indicating that a redistribution of water inside the cell occurs during compression and enforcing the original hypothesis that in guanosine phases water separates into different regions. Moreover, changes in free energy were calculated, and helix elastic constants were derived.

Temperature and pressure limits of guanosine monophosphate self-assemblies

“…In case of the 5′-GMP self-assembly, the observed pressure resistance of the longitudinal dimension and thus the stacking interaction can be explained by the same mechanism. In the liquid-crystalline phase, where the 5′-GMP quartet stacks are hexagonally arranged, the stacking distance has been shown to be decreased upon compression 67 . Further, an acidic shift of the water pH upon pressurization would lead to partial protonation of the doubly charged phosphate groups, thus reducing the electrostatic repulsion between adjacent guanine bases 68 .…”

Recent Advances in the Design of Polymerizable Lyotropic Liquid‐Crystal Assemblies for Heterogeneous Catalysis and Selective Separations

“…Part of the impetus behind this aspect of the work was to see if a purely organic chiral molecular-sieve analogue could be formed, given the potential of some LLC molecules to self-assemble into chiral superstructures. [47] Since no sign of chiral superstructure was observed with the achiral counter ions, it was hoped that chiral counter ions might have a cooperative affect with the chiral headgroup in forming a chiral supramolecular assembly. However, enantiomers of tartaric acid were not found to have any observable effect on the LLC phase (or catalytic) behavior of 8.…”

How soft are biological helices? A measure of axial and lateral force constants in folate quadruplexes by high-pressure X-ray diffraction

“…Concerning structural properties, it was observed that the length of the quadruplexes strongly depends on stacking interactions (3,7,8), and that preferential hydration effects occur during swelling (i.e., the lateral and end-to-end axial inter-helix distances do not change uniformly) (9,10). Moreover, osmotic stress measurements showed that lateral forces dominating at short helix separations are hydrational and that a balance between medium-range attraction, which induces the selfassembly, and short-range repulsion, which prevents the contact between quadruplexes, is implied (11,12).…”