73 Molecules Talk: Selecting Molecular Communication and Complexity
73 Molecules Talk: Selecting Molecular Communication and Complexity
In our complex human society, we define communication by its specificity. Without a careful choice of words, our speech would be at best, a source of magnificent misunderstanding, or just plain babel! What does this mean for prebiotic chemistries?
In terms of prebiotic chemical evolution, selection by definition would have favored protective accumulation of longer-lived molecular aggregates. Over time, the same selective imperatives would create webs of such aggregates, increasing the range and specificity of molecular interactions in a challenging environment. If this were to have occurred in an enclosed proto-cellular space, it should have resulted in a primitive molecular communication and a growing complexity (another property of life!). In fact, alof the properties of life must have accompanied the achievement of more and more complex intermolecular communication. Simply put, a prebiotic (or for that matter a cellular) genetic change that alters the rate of one catalytic reaction (if not destructive) will drive the selection of changes in components of other, interconnected metabolic chemistries. If molecular communication required the evolution of catalytic specificity, then the final elaboration of complexity and order as a property of life further requires the selection of mechanisms of regulation and coordination.
Intermolecular Communication Leads to an Early Establishment of Essential Interconnected Chemistries
Earlier, we suggested that inorganic catalyst precursors to biological enzymes were probably minerals embedded in clay or other substrata, providing surfaces that would naturally aggregate organic molecules and catalyze repetitive reactions. Either the initial objects of prebiotic selection included external stable monomers and polymers, outside or as seems more likely, inside proto-cells. Later, selection would have favored polymers that enhanced growth and reproduction of successful aggregates. These polymers were likely those that catalyzed their own synthesis, perhaps collaborating with inorganic catalytic minerals. The result would be the elaboration of a web of interconnected chemical reactions between molecules with high affinity for each other, thereby increasing the specificity of those reactions. In the context of life origins and evolution, co-catalysis describes the activities of these interconnected metabolic reactions.
As noted, high-affinity interactions are inherently protective. During prebiotic chemical/metabolic evolution, protected stable molecular assemblies would be targets of selection. Continuing co-evolution of catalysts, substrates and co-catalytic reaction sets would lead to more and more sophisticated molecular communication. Once established, efficient biochemical reaction sets would be constrained against significant evolutionary change. Any change (mutation) that threatened this efficiency would mean the end of a prebiotic chemical