Organic microstructures and terrestrial protocells.

This letter concerns several issues in Folsome's recent paper on "Synthetic Organic Microstructnres and the Origins of Cellular Life" [1]. Thereismuch agreement [2, 3] that facile early formation of cell-like structures from (appropriate) nonbiological polymers is a crucial question [4]. However: 1. The answer to Folsome's question of "Why Haven't Microstructures Been Seen Before in Spark-Discharge Experiments?" is that they have been. Such publication is by Grossenbacher and Knight, in a volume which Folsome cites for other reasons [5]. The Grossenbacher-Knight microstructures contain more than 10% carbon. Those authors infer special properties for the" organic content,. What makes the proteinoid microspheres of overall interest is their many functions [6] beyond their varied complex morphologies. 2. Several chemical statements of Folsome's are already answered in a paper in Naturwissenschaften [7] cited by him for other purposes. Any evaporative process would necessarily result in concentrating amino acids and also their thermal polymers [7] since both are of very low volatility. The reason for low volatility is, of course, that e-amino acids, H3+NCHRCOO -, are virtually the only ampholytic micromolecules found from either lunar or meteoritic material, or in heuristic laboratory experiments [6]. Polyamino acids obtained by heating ofc~-amino acids are also nonvolatile. If one assume other compounds such as urea, hydroxy acids, nitriles, etc. to have been formed, those compounds were bound to have been more volatile than ampholytes of either low or high molecular weight. Experiments done with such volatile organic compounds have accordingly seemed not to require publication, although results with minerals, which are nonvolatile, have merited reporting [8]. Folsome's imputation that dicarboxylic amino acids must be present in excess over other amino acids in amino acid reaction mixtures is false [9-13]. Folsome's imputed "overheated" locales, such as lava flows, are likewise falsely based. Temperatures as low as 65 ~ have been demonstrated for polymerization of amino acids [13-16] and are plausible for the early Earth. Folsome's comments on fi and c~ linkages in protein and proteinoids are unsupported for protobiogenesis; reasons why the comments of Andini [17] and Temussi [18] are indefensible have been explained [13, 19]. The presence of seawater salts can help, rather than hinder, the formation of meaningful polymers [15]. In the light of selectively low volatility of amino acids and their polymers, one can add to the concentrative mechanisms proposed by Dose [20], the conditions of fresh water and estuarine events as well. A wide range of ratios of amino acid: mineral saltswould thus be possible. 3. The ungeologicality of spark-discharge experiments in gases within closed flasks, as conducted by Folsome et al. [21], has been emphasized and explained in recent years [13, 22, 23], especially for the high yields found in closed flasks. As Florkin [22] indicated, the 75% I-I 2 in gases in flasks energized by electric discharge are without terrestrial counterpart. For this and other reasons, the alleged potential of Folsome's organic microstructures seems to me to be poorly supported; until functions are demonstrated, their occurrence is only a priori assumption for any given microstructure. Folsome's "faint hint" [21] of amino acid contents suggests contamination; his failure to find the kind of catalytic activities that is known to be abundant in thermal copolyamino acids [6] raises serious questions about what he is looking at. Experiments yielding activity [6] and those not doing so [211 contribute to the inference that protoenzymic activity on the early Earth was supported by copolyamino acid structure. Basically, Folsome's "polymers" are uncharacterized; nor have they been shown to be polymers. In summary, Folsome's paper fails to report on much that has been done and inferred [6, 24] and, in my judgment, it extrapolates from inadequate evidence and overstates the significance of his products for a context of protobiogenesis.