“On the transition from prebiotic vesicles to protocellular membranes” – IAS Research Seminar by Kepa Ruiz-Mirazo and Sara Murillo

Kepa Ruiz-Mirazo and Sara Murillo will be giving a talk entitled ‘On the transition from prebiotic vesicles to protocellular membranes‘.

Date and place: 9th of October 2012, at 11.00, Room B14, Carlos Santamaría Building.

Abstract: It is well known that the generation of a physical border (a membrane) is a crucial step to the generation of a system with some kind of autonomy. Spatial separation of the internal and external medium allows the system to generate a minimally stable micro-environment (controlling concentration, energy-flow and osmosis) in which a metabolic reaction network could lodge inside maintaining the distinctive far from equilibrium dynamics of the autonomous systems.

In this autonomous context, in which the system has to self-constructed and self-maintained, generation of a compartment is achieved by self-assembly molecules which generates a semi-permeable barrier closely connected to the reaction network (being condition and result of it) and playing an active role in the interaction with the environment, regulating and controlling matter and energy exchanges with it.

Nowadays, these kinds of membranes are made of lipids (amphiphilic molecules that possess both polar and apolar parts) but they have a complicated generation process (which, besides, involves complex molecules). However, there is a different sort of molecules with the same amphiphilic properties which are enough simple to be present in the origin of protocellular systems, the fatty acids. Differences between amphiphile composition and mixtures with other simple molecules show differences on the stability, permeability and self-assembling capacities of such membranes. In general, more complexity means a stability profit and a permeability loss but is has been seen that mixtures of simple molecules allow a wide range of both.

Moreover, in order to be efficient and sufficiently robust, the set of endergonic-exergonic couplings underlying work production in the system has to be, in addition, well regulated. Nowadays this is carried out by enzymes, which change activation energies and regulate metabolic reactions in very sophisticated ways. But at the first stages of the origin these systems, the job ought to be done by more rudimentary catalysts, perhaps oligopeptides or smaller multimers, whose formation would be favored in the context of lipidic or fatty acid self-assembled structures, such as primitive vesicles.

In this talk we will focus on two recently published papers showing new out comings of  experiments with amphiphile mixtures and our future experimental projects about insertion of small peptides in the fatty-acids membrane, based on the `lipid-peptide protocell model´ (Ruiz-Mirazo & Mavelli, 2008) previously in sillico developed.