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Table 3 Comparison of the physical and geological characteristics of the two divalent cations under study as putative signs in this paper

From: Empirical demonstration of environmental sensing in catalytic RNA: evolution of interpretive behavior at the origins of life

Chemical properties Modern conditions Early life conditions
Cation Hydration number Ionic radius (Å) pK a Hardness (η c) Oceans (mM) Cells (mM) Archaean ocean (%) Hydrothermal vents (mM) Affinity for montmorillonite clay ( k a/ k Cd)
Mg2+ 6 0.72 11.42 47.59 50 30 24 51 0.9
Ca2+ 8 1.12 12.70 19.52 10 1 29 232 5.8
  1. Data taken from references [15]-[18].