Synthesis of life in the lab? Defining a protoliving system.

The synthesis of a living system in the lab has been judged by a number of critics as partly attained by the proteinoid microsphere because of its primitive properties of metabolism, growth, and reproduction. These same critics, however, judge the organism as not alive, or as being 50 to 75 percent alive (Baltscheffsky and Jurka, 1984), owing to the absence of a nucleic acid genetic coding mechanism. The experiments in retracing evolution suggest, however, that the self-sequencing of amino acids was the evolutionary precursor of modern nucleic acid templating; the genetic memory is the molecule. The proteinoid microsphere is not a modern living system, but does represent at least a protoliving system (Fox and Dose, 1972). Berra (1990, p. 75) has commented on other difficulties in defining a protoliving system. In Berra's opinion, metabolism, reproduction, responsiveness to stimuli, and cellularity constitute or describe aliveness. These properties characterize proteinoid microspheres. A number of experiments demonstrate that amino acids in aminoacyl adenylates yield specific products, whereas nucleotides are without effect. For this and related reasons, especially the demonstrated self-sequencing of amino acids when they are warmed, resultant bio-functional properties of self-assembled microstructures, and demonstrated self-sequencing of amino acids in modern systems, the results appear to bridge from the chemical era to the biological period. All the above emerges from a departure in style of research (Young, 1984; Pauling and Zuckerkandl, 1972). The latter authors said, "It appears likely that biogenesis is the passage from a 'non-living system' existing in a large number of states to a 'living' system also existing in a large number of states."(ABSTRACT TRUNCATED AT 250 WORDS)