Structural Responses of Nucleic Acids to Mars-Relevant Salts at Deep Subsurface Conditions

Abstract

High pressure deep subsurface environments of Mars may harbor high concentrations of dissolved salts, such as perchlorates, yet we know little about how these salts influence the conditions for life, particularly in combination with high hydrostatic pressure. We investigated the effects of high magnesium perchlorate concentrations compared to sodium and magnesium chloride salts and high pressure on the conformational dynamics and stability of double-stranded B-DNA and, as a representative of a non-canonical DNA structure, a DNA-hairpin (HP), whose structure is known to be rather pressure-sensitive. To this end, fluorescence spectroscopies including single-molecule FRET methodology were applied. Our results show that the stability both of the B-DNA as well as the DNA-HP is largely preserved at high pressures and high salt concentrations, including the presence of chaotropic perchlorates. The perchlorate anion has a small destabilizing effect compared to chloride, however. These results show that high pressures at the kbar level and perchlorate anions can modify the stability of nucleic acids, but that they do not represent a barrier to the gross stability of such molecules in conditions associated with the deep subsurface of Mars.

Behavior of B- and Z-DNA Crystals under High Hydrostatic Pressure

“…The stability of the DNA duplex has long been investigated as a function of temperature [4,5], but there have been relatively few studies of the effects of hydrostatic pressure [7,28,29]. The helix-coil transition temperature Tm is the characteristic parameter that defines how the duplex resists unwinding and the denaturation (separation in single strands) induced by heat.…”

“…The helix-coil transition temperature Tm is the characteristic parameter that defines how the duplex resists unwinding and the denaturation (separation in single strands) induced by heat. As far as pressure is concerned, exhaustive studies were less documented until recently [28,29]. As the Watson-Crick base pairing is associated with a negative DV, it was just concluded that DNA would be stabilized by (or at least very resistant to) external pressure [6].…”

“…As the Watson-Crick base pairing is associated with a negative DV, it was just concluded that DNA would be stabilized by (or at least very resistant to) external pressure [6]. Altogether, these studies concluded that, in the case of linear DNA duplexes "H-bonding and p-p-stacking interactions are marginally affected by pressure" [7,29]. However, this would be less true in the case of RNAs [30,31] or ribozymes, where structural bends, twists, and cavities are, as in proteins, dominant structural features, and, consequently, pressure-induced changes may alter their biochemical activities.…”

“…The tools available to study pressure effects are mainly spectroscopic techniques, IR and UV spectroscopy, and NMR and X-ray crystallography, for a review see [32]. For the dependency of Tm versus pressure, see [29,33].…”

Harnessing Pressure-Axis Experiments to Explore Volume Fluctuations, Conformational Substates, and Solvation of Biomolecular Systems

“…(B) Graphical schematic summary of the conformational changes of the human telomeric G-quadruplex (G4Q) as a function of temperature, pressure, and cosolutes. The osmolyte TMAO and the crowding agent Ficoll 70, a polysaccharide of 5 nm hydrodynamic radius, as well as salt (Na + ) shift the equilibrium toward the antiparallel conformation. , Medium high temperatures and pressures lead to an equilibrium shift toward the parallel/hybrid conformation of the G4Q, higher temperatures and pressures finally to the unfolding of the G-quadruplex structure.…”