Melanoidin and aldocyanoin microspheres: Implications for chemical evolution and early precambrian micropaleontology

Abstract

Two new classes of organic microspheres are described. One of them (melanoidin) is synthesized from amino acids and sugars in heated aqueous solutions. The other (aldocyanoin) is formed in aqueous solutions of ammonium cyanide and formaldehyde at room temperature. The general properties of these microspheres, including conditions of synthesis, size and shape, mechanical and pH stability, and solubility, are compared with corresponding properties of other "protocell" model systems. It is concluded that melanoidin and aldocyanoin microsphreres are plausible candidates for precellular units in the primitive hydrosphere. Since the bulk of the organic carbon in early Precambrian sediments is insoluble kerogen-melanoidin, it is suggested that some Precambrian "microfossils" may be abiotic melanoidin microspheres of the type described herein.

Aldocyanoin microspheres: Partial amino acid analysis of the microparticulates formed from simple reactants under various conditions

“…The procedures of Kenyon and Nissenbaum (1976) were followed. Aqueous solutions of NaCN (0.2 M), NH4C1 (0.2 M), HCHO (0.2 M), and NH4SCN (0.02 M) were mixed and adjusted to pH 9.3 in 250 ml glass-stoppered erlenmeyer flasks.…”

“…In some studies, no energy source was used; in others, ultraviolet light or heat was used to cause molecular transformations that frequently resulted in microparticulate material morphologically resembling bacteria or fungi. Folsome et al (1975Folsome et al ( , 1976, Smith et al (1969), and Kenyon and Nissenbaum (1976) have cautioned that some of these aldehyde-aminecyanide microspheres, which could have formed during the chemical evolution of early prebiotic times, might be mistaken for microfossils by micropaleobiologists who rely heavily on morphological features as criteria for biogenicity. Schopf (1975) has also critically reviewed the problems of precambrian paleobiology.…”

“…We feel that this model is far too contrived and implausible and will comment no further. Nissenbaum et al (1975) and Kenyon and Nissenbaum (1976) reviewed and discussed some protocell models and correctly pointed out that certain aldehyde-amine or aldehyde-ammonia reactions occur.rapidly in aqueous solutions (forming Schiff bases), and that these are dehydration reactions that can and do often yield polymers or, at least, macromolecular materials. Kenyon and Nissenbaum (1976) studied a simple model and showed that microspheres were formed, which morphologically mimic cocci bacteria.…”

“…Nissenbaum et al (1975) and Kenyon and Nissenbaum (1976) reviewed and discussed some protocell models and correctly pointed out that certain aldehyde-amine or aldehyde-ammonia reactions occur.rapidly in aqueous solutions (forming Schiff bases), and that these are dehydration reactions that can and do often yield polymers or, at least, macromolecular materials. Kenyon and Nissenbaum (1976) studied a simple model and showed that microspheres were formed, which morphologically mimic cocci bacteria. Other investigators (Herrera, 1940;Smith et al, 1968Smith et al, , 1969Smith et al, , 1971Labadie et al, 1967aLabadie et al, , 1967bLabadie et al, , 1968 have studied mixtures involving cyanide, thiocyanate, ammonium ion and/or an aldehyde, or glycine.…”

“…Schopf (1975) has also critically reviewed the problems of precambrian paleobiology. Kenyon and Nissenbaum (1976) briefly studied a simple aldocyanoin mixture and described its morphological features, but did not report on the composition or other analytical facts of the microspheres in the mixture. All of the reported experiments were carried out aerobically.…”