Spontaneous structural developments of a peptide-vesicle system under conditions of the early continental crust

Spontaneous structural developments of a peptide-vesicle system under conditions of the early continental crust Christian Mayer 1, Ulrich Schreiber 2, María J. Dávila 1, Oliver J. Schmitz 3 1  Institute of Physical Chemistry, CENIDE, University of Duisburg-Essen, 45141 Essen, Germany 2  Department of Geology, University of Duisburg-Essen, 45141 Essen, Germany; 3 Institute of Applied Analytical Chemistry, University of Duisburg-Essen, 45141 Essen, Germany;   Life is characterized by significant complexity combined with a high degree of order. Therefore, early steps towards the origin of life must have necessarily led into this direction. The most powerful process leading to states of increased complexity and order is Darwinian evolution. However, this requires self-reproducing systems. So which processes, instead of Darwinian evolution, could have developed complex prebiotic structures in the early beginnings? First, a necessary precondition for development is a permanent non-equilibrium state. This is most easily achieved by a constant variation of physical conditions, such as switching between states of wetness and dryness, or by fluctuating temperature or pressure conditions. This combined with the formation and selection of complex molecular structures has the power to lead from simple chaotic mixtures toward larger, more defined entities. Perfect conditions for such a development are found in the Earth’s crust. Recent experiments in our lab rely on pressure cycling, simulating the conditions in the Earth’s crust in a depth of 1 km. We can show that, in presence of simple prebiotic molecules, these conditions lead to the periodic formation of vesicles. These vesicles in turn select peptides generated randomly in a pool of amino acids. The resulting vesicle-peptide structures are constantly selected for their stability, leading to an ongoing optimization process. In total, a process is formed which leads to continuous increase in order (selected peptide sequences) and complexity (growing size of the peptides).  The experimental result of such an autonomous selection process is a functional peptide struc­ture formed inside a membrane of the “surviving” vesicles. It has the capability to stabilize the vesicle, alter its size and allow for an increased water permeability in order to reduce osmotic pressure load.   References   Mayer, C., Schreiber, U., Dávila M. (2015) Periodic vesicle formation in tectonic fault zones – an ideal scenario for molecular evolution, Origins of Life and Evolution of Biospheres 45: 139-148. Mayer, C., Schreiber, U., Dávila, M. (2017) Selection of prebiotic molecules in amphiphilic environments, Life 7: 3. Mayer, C., Schreiber, U., Dávila, M., Schmitz, O.J. et al. (2018) Molecular evolution in a peptide-vesicle system, Life 8: 16. Mayer, C. (2020) Life in the context of order and complexity, Life 10, 5. Davila, M., Mayer C. (2022) Membrane structure obtained in an experimental evolution process, Life 12: 145. Davila, M., Mayer C. (2023) Structural phenomena in a vesicle membrane obtained through an evolution experiment, Life 13: 1735.