Amino acids on the rampant primordial Earth: Electric discharges and the hot salty ocean

261

188

The action of an electric discharge on reduced gas mixtures such as H(2)O, CH(4) and NH(3) (or N(2)) results in the production of several biologically important organic compounds including amino acids. However, it is now generally held that the early Earth's atmosphere was likely not reducing, but was dominated by N(2) and CO(2). The synthesis of organic compounds by the action of electric discharges on neutral gas mixtures has been shown to be much less efficient. We show here that contrary to previous reports, significant amounts of amino acids are produced from neutral gas mixtures. The low yields previously reported appear to be the outcome of oxidation of the organic compounds during hydrolytic workup by nitrite and nitrate produced in the reactions. The yield of amino acids is greatly increased when oxidation inhibitors, such as ferrous iron, are added prior to hydrolysis. Organic synthesis from neutral atmospheres may have depended on the oceanic availability of oxidation inhibitors as well as on the nature of the primitive atmosphere itself. The results reported here suggest that endogenous synthesis from neutral atmospheres may be more important than previously thought.

Section: Discussionsupporting

confidence: 86%

A Reassessment of Prebiotic Organic Synthesis in Neutral Planetary Atmospheres

Cleaves

Chalmers

Lazcano

et al. 2008

261

188

“…Miller (1953) was the first who showed that the synthesis of amino acids was possible from a mixture of gases. Table 5 shows several protein amino acids as well as non-protein amino acids that were synthesized in environments simulating the atmosphere of prebiotic earth (Janda et al 2008;Ruiz-Bermejo et al 2007;Plankensteiner et al 2006;Civiš et al 2004;Miyakawa et al 2002;Kobayashi et al 2001;Kobayashi et al 1999b;Miyakawa et al 1999;Takahashi et al 1999;Kobayashi et al 1998;Hirose et al 1990Hirose et al -1991Kobayashi et al 1990;Schlesinger and Miller 1983;Shimoyama et al 1978;Becker et al 1974;Sagan and Khare 1971;Bar-Nun et al 1970;Miller 1953).…”

Section: Sources Of Amino Acids On the Prebiotic Earthmentioning

confidence: 99%

“…Most of the amino acids shown in Table 5 have also been found in ISM simulation experiments (Table 1) and in meteorites (Tables 2, 3, 4). However, there are two amino acids (α-lysine-traces, α-histidine-traces) synthesized by Plankensteiner et al (2006) (redox-neutral atmospheres), one (α-histidine-trace) synthesized by Ruiz-Bermejo et al (2007) and one (α-asparagine) synthesized by Civiš et al (2004) (redox-neutral atmospheres) that were not synthesized in ISM experiments (Table 1) or found in meteorites (Tables 2, 3, 4). Nuevo et al (2008) were not able to confirm the synthesis of α-histidine and α-lysine in ISM experiments.…”

Section: Endogenous Amino Acidsmentioning

confidence: 99%

Which Amino Acids Should Be Used in Prebiotic Chemistry Studies?

Zaia

Santana

2008

134

103

The adsorption of amino acids on minerals and their condensation under conditions that resemble those of prebiotic earth is a well studied subject. However, which amino acids should be used in these experiments is still an open question. The main goal of this review is to attempt to answer this question. There were two sources of amino acids for the prebiotic earth: (1) exogenous -- meaning that the amino acids were synthesized outside the earth and delivered to our planet by interplanetary dust particles (IDPs), meteorites, comets, etc. and (2) endogenous -- meaning that they were synthesized on earth in atmospheric mixtures, hydrothermal vents, etc. For prebiotic chemistry studies, the use of a mixture of amino acids from both endogenous and exogenous sources is suggested. The exogenous contribution of amino acids to this mixture is very different from the average composition of proteins, and contains several non-protein amino acids. On the other hand, the mixture of amino acids from endogenous sources is seems to more closely resemble the amino acid composition of terrestrial proteins.

“…Only a few works describe the effect of saline solutions in this type of experiment (Plankensteiner et al 2006;Manolache et al 1997;Kobayashi et al 1990). Nonetheless, it has been postulated that the ancient sea had a salinity of the 1.5 to 2 times the modern value (Knauth 2005; Morse and Mackenzie 1998) and a pH=4-10, although the pH value of early ocean water is under debate (see Kempe and Kazmierczak 2002;Morse and Mackenzie 1998;Russell and Hall 1997;Williams and Frausto da Silva 1996;Bada et al 1994;Macleod et al 1994;Grotzinger and Kasting 1993;Kasting 1993;Gregor et al 1988;Holland et al 1986;Walker 1985).…”

Section: Introductionmentioning

confidence: 99%

The Effects of Ferrous and other Ions on the Abiotic Formation of Biomolecules using Aqueous Aerosols and Spark Discharges

Ruíz-Bermejo

Menor‐Salván

Osuna‐Esteban

et al. 2007

It has been postulated that the oceans on early Earth had a salinity of 1.5 to 2 times the modern value and a pH between 4 and 10. Moreover, the presence of the banded iron formations shows that Fe(+2) was present in significant concentrations in the primitive oceans. Assuming the hypotheses above, in this work we explore the effects of Fe(+2) and other ions in the generation of biomolecules in prebiotic simulation experiments using spark discharges and aqueous aerosols. These aerosols have been prepared using different sources of Fe(+2), such as FeS, FeCl(2) and FeCO(3), and other salts (alkaline and alkaline earth chlorides and sodium bicarbonate at pH = 5.8). In all these experiments, we observed the formation of some amino acids, carboxylic acids and heterocycles, involved in biological processes. An interesting consequence of the presence of soluble Fe(+2) was the formation of Prussian Blue, Fe(4)[Fe(CN)(6)](3), which has been suggested as a possible reservoir of HCN in the initial prebiotic conditions on the Earth.