Catalytic effects of Murchison Material: Prebiotic Synthesis and Degradation of RNA Precursors

Abstract

Mineral components of the Murchison meteorite were investigated in terms of potential catalytic effects on synthetic and hydrolytic reactions related to ribonucleic acid. We found that the mineral surfaces catalyzed condensation reactions of formamide to form carboxylic acids, amino acids, nucleobases and sugar precursors. These results suggest that formamide condensation reactions in the parent bodies of carbonaceous meteorites could give rise to multiple organic compounds thought to be required for the emergence of life. Previous studies have demonstrated similar catalytic effects for mineral assemblies likely to have been present in the early Earth environment. The minerals had little or no effect in promoting hydrolysis of RNA (24mer of polyadenylic acid) at 80°C over a pH range from 4.2 to 9.3. RNA was most stable in the neutral pH range, with a half-life ~5 h, but at higher and lower pH ranges the half-life decreased to ~1 h. These results suggest that if RNA was somehow incorporated into a primitive form of RNA-based thermophilic life, either it must be protected from random hydrolytic events, or the rate of synthesis must exceed the rate of hydrolysis.

Formamide and the origin of life

“…These data are of particular interest providing the first example on the catalytic effect of a meteorite on the synthesis of nucleic bases ( Fig. 2 and Scheme 1 pathway "L") [96].…”

“…From the one-carbon atom formamide the RNA precursors are simply obtained by warming at 160 • C [80,96] or by decreasing the temperature while providing part of the energy in the form of UV radiation [81,82]. These synthetic reactions occur in the presence of any one of the following common terrestrial minerals: calcium carbonate, zeolite, alumina, titanium oxides, clays, olivines, phosphates (reviewed in [27,80]), and of iron-sulphur-copper minerals [87], zirconium minerals [89], borates [93]; or, from outer environments, in the presence of Murchison meteorite minerals [96].…”

“…These synthetic reactions occur in the presence of any one of the following common terrestrial minerals: calcium carbonate, zeolite, alumina, titanium oxides, clays, olivines, phosphates (reviewed in [27,80]), and of iron-sulphur-copper minerals [87], zirconium minerals [89], borates [93]; or, from outer environments, in the presence of Murchison meteorite minerals [96]. The generality of the catalysts involved indicates the non-fastidious nature of the synthetic process of nucleic acids precursors based on formamide chemistry.…”

Formation of nucleobases in a Miller–Urey reducing atmosphere

“…In 2001, Saladino, Di Mauro, and coworkers (14) proposed that the parent molecule for the one-pot synthesis of nucleobases is formamide (15)(16)(17)(18)(19)(20)(21)(22)(23). Their team, together with other authors, demonstrated the formation of (not only) fundamental nucleobases for the origin of RNA in experiments involving the heating of formamide in presence of manifold catalysts (17,(24)(25)(26), upon UV irradiation (27), proton (28) and heavy-particle radiation (29), exposition to shock waves (18), etc. Recently, Hörst et al (30) also referred to a positive result on qualitative detection of RNA nucleobases and manifold amino acids from tholines created in a N 2 , CH 4 , CO mixture.…”

Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

“…Evidence of the catalytic properties of meteorites in prebiotic chemistry was recently provided by thermal processes of condensed-phase FA at relatively high temperatures (333 and 413 K) (57,58) or at the most extreme temperature conditions modeling impact events in Earth's atmosphere or surface (3,59). During their wandering, meteorites are exposed, under an extreme variety of temperature conditions, to ionizing radiation of cosmic origin (60) able to excite and dissociate FA (the ionization energy of the FA being ∼11-15 eV).…”