Biomolecular self-assembly under extreme Martian mimetic conditions

Abstract

The recent discovery of subsurface water on Mars has challenged our understanding of the natural limits of life. The presence of magnesium perchlorate (Mg(ClO₄)₂) on the Martian surface raises the possibility that it may also be present in this subsurface lake. Given that the subsurface lakes on Earth, such as Lake Vostok and Lake Whillans, are capable of harbouring surprising amounts of life, these new findings raise interesting possibilities for how biomolecules might self-assemble in this environment on Mars. Here we investigate the self-association and hydration of the amino acid glycine in aqueous Mg(ClO₄)₂ at 25°C and −20°C using neutron diffraction with hydrogen isotope substitution and subsequent analysis with empirical potential structure refinement to yield a simulated box of atoms consistent with the scattering data. We find that although the highly chaotropic properties of Mg(ClO₄)₂ disrupt the hydration and hydrogen bonding ability of the amino acid, as well as the bulk water structure, glycine molecules are nonetheless still able to self-associate. This occurs more readily at lower temperature, where clusters of up to three molecules are observed, allowing us to speculate that the formation of biological molecules is possible in the Martian environment.

GRAPHICAL ABSTRACT

KEYWORDS:

• Neutron diffraction
• empirical potential structure refinement
• amino acid
• water
• clustering

Acknowledgements

Experiments at the ISIS Pulsed Neutron Facility were supported by a beam time allocation from the Science and Technology Facilities Council under proposal number RB 1800054. The authors thank Tristan Youngs for his support during the running of the neutron diffraction experiments.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Harrison Laurent http://orcid.org/0000-0002-8925-4773

Lorna Dougan http://orcid.org/0000-0002-2620-5827

Additional information

Funding

The project was supported by a grant from the Engineering and Physical Sciences Research Council (EPSRC) [grant number EP/P020088X/1] to Dr L. Dougan. Harrison Laurent is jointly supported by an EPSRC DTA studentship and an ISIS Facility Development Studentship.