Although the mechanism described above explains the results of the experimental #MLN4924 randurls[1|1|,|CHEM1|]# L-Glu peptide formations in the presence of K+ and Na+, this interpretation of the mechanism is not exhaustive. Our data on the calculated difference between the K+ and Na+ diffusion-controlled condensation of amino acids is fully consistent with the experimental data (Fig. 2). Using the model above for other mono- and divalent ions, we summarised in Fig. 3 the available data on diffusion coefficients,
hydration energy of the ions and their coordination to the amino acids in aqueous solutions (Lide and David 1998; Schmid et al. 2000; Jockusch et al. 2001; Remko and Rode 2006). We found that Rb+ and Cs+ might be similar to K+ in mediating peptide formation in the OO coordination to amino acids, which has not yet been modelled, to the best of our knowledge. Fig. 3
Metal ion diffusion, hydration and coordination to amino selleck chemicals llc acids. The coordination of the ions to amino acids in aqueous solutions is shown in parentheses. The most abundant ions are shown in bold Taken together, our experimental and theoretical evidences show that K+ predominates over Na+ ions in the formation of peptides. This allows us to suggest that the high K+/Na+ ratio in any prebiotic water reservoir could accelerate the
first step in the chemical evolution of self-assembling organic molecules. Geochemically, a high K+/Na+ ratio in aqueous solution could also have formed during the differentiation of primary chondritic material into the Earth’s core and Avelestat (AZD9668) mantle (Galimov et al. 2011). It was also suggested that the ion composition required for the initial environment for the first cells could have emerged in inland geothermal ponds (Mulkidjanian et al. 2012). Although this assumption has been criticised (Switek 2012), from a biological point of view, the “modern” cytoplasm of the living cells might represent the same functional conditions that determined the first protocell’s chemical content. Thus, if the emergence of the ancient metabolic and information systems of the protocells occurred in potassium-rich habitats, it seems evident that all the living cells would have evolved to preserve the initial ion gradients by using energy-dependent membrane pumps in sodium aqueous media.