Abstract:
Critical experimental design issues connecting energy transduction and inheritable information within a protocell are explored and elucidated. The protocell design utilizes a photo-driven energy transducer (a ruthenium complex) to turn resource molecules into building blocks, in a manner that is modulated by a combinatorial DNA-based co-factor. This co-factor molecule serves as part of an electron relay for the energy transduction mechanism, where the charge-transport rates depend on the sequence that contains an oxo-guanine. The co-factor also acts as a store of inheritable information due to its ability to replicate non-enzymatically through template-directed ligation. Together, the energy transducer and the co-factor act as a metabolic catalyst that produces co-factor DNA building blocks as well as fatty acids (from picolinium ester and modified DNA oligomers), where the fatty acids self-assemble into vesicles on which exterior surface both the co-factor (DNA) and the energy transducer are anchored with hydrophobic tails. Here we use simulations to study how the co-factor sequence determines its ‘fitness’ as reflected by charge transfer and replication rates. To estimate the impact on the protocell, we compare these rates with previously measured metabolic rates from a similar system where the charge transfer is directly between the ruthenium complex and the oxo-guanine (without DNA replication and charge transport). Replication and charge transfer turn out to have different and often opposing sequence requirements. Functional information of the co-factor molecules is used to probe the feasibility of randomly picking co-factor sequences from a limited population of co-factors molecules, where a good co-factor can enhance both metabolic biomass production and its own replication rate. Thus, the co-factor composition / sequence can be interpreted as primitive biological information when selection from a combinatorial set of co-factors is possible. Further, the transition from nonliving to living matter for the system is likely discontinuous in protocellular biomass if the free parameter is the net growth rate determined by the co-factor. Amplification, selection, and evolution of co-factors can only occur once a co-factor is randomly ‘discovered’ that operates above this critical discontinuous threshold. Thus, this critical point is also the onset of Darwinian evolution.
Main reference: Kristoffer Thomsen, Artemy Kolchinsky, Steen Rasmussen, arXiv 2024
Speaker
Steen RasmussenExternal Professor