Possible Prebiotic Condensation of Mononucleotides by Cyanamide

Ibáñez, Jorge Díaz; Kimball, A. P.; Oró, J.

doi:10.1126/science.173.3995.444

Cited by 86 publications

(27 citation statements)

References 18 publications

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“…Techniques used for the phosphorylation of organics include adding condensing agents to mixtures of orthophosphate and organics (7), heating orthophosphate with organics (8, 9), adding condensed phosphates to organics (10), or a combination of these methods (7,11,12). Geochemical environments where these processes may take place include a dry pond with wet/dry cycles (12), hydrothermal vents (4), or mineral surfaces (2,10).…”

Section: Phosphorus In the Origin Of Lifementioning

confidence: 99%

Rethinking early Earth phosphorus geochemistry

Pasek

2008

Proc. Natl. Acad. Sci. U.S.A.

235

209

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Phosphorus is a key biologic element, and a prebiotic pathway leading to its incorporation into biomolecules has been difficult to ascertain. Most potentially prebiotic phosphorylation reactions have relied on orthophosphate as the source of phosphorus. It is suggested here that the geochemistry of phosphorus on the early Earth was instead controlled by reduced oxidation state phosphorus compounds such as phosphite (HPO 3 2؊ ), which are more soluble and reactive than orthophosphates. This reduced oxidation state phosphorus originated from extraterrestrial material that fell during the heavy bombardment period or was produced during impacts, and persisted in the mildly reducing atmosphere. This alternate view of early Earth phosphorus geochemistry provides an unexplored route to the formation of pertinent prebiotic phosphorus compounds, suggests a facile reaction pathway to condensed phosphates, and is consistent with the biochemical usage of reduced oxidation state phosphorus compounds in life today. Possible studies are suggested that may detect reduced oxidation state phosphorus compounds in ancient Archean rocks.meteorites ͉ origins of life ͉ phosphonates ͉ prebiotic ͉ redox chemistry P hosphorus (P) is a key biologic element and is the limiting reagent in many ecosystems. Phosphorus is ubiquitous in biochemistry because phosphorylated biomolecules play major roles in replication and information (as RNA and DNA), metabolism (as ATP, NADPH, and other coenzymes), and structure (as phospholipids). Several key properties of P as phosphate make it advantageous to biologic systems, including thermodynamic instability coupled with kinetic stability, charge and coordination state, and a constant oxidation state under typical redox conditions (1). These features are especially critical to the formation of large informational polymers, and hence highly relevant to the origin and development of early life. Phosphorus Geochemistry and CosmochemistryThe major forms of P in life are summarized in Fig. 1. Inorganic P compounds used by life include orthophosphate, pyrophosphate and other condensed phosphates, phosphite, hypophosphite, and phosphine. These inorganic forms are either used by organisms as sources of P for the synthesis of organic-P biomolecules or are possible metabolic by-products of P metabolism (PH 3 ). Additionally, orthophosphate acts as a buffer in many cells, keeping pH constant at Ϸ7. Organic forms of P include compounds with C-O-P linkages and compounds with C-P linkages, and both are formed from inorganic P by using enzymes.Phosphorus is a lithophile element at the redox conditions on the surface of the Earth, and hence orthophosphate is the dominant form of inorganic P on the surface of the Earth today. The concentration of orthophosphate is water-buffered by the solubility of orthophosphate minerals like apatite, Ca 5 (PO 4 ) 3 (OH,F,Cl), on the present-day Earth, and of whitlockite, Ca 9 MgH(PO 4 ) 7 , and brushite, CaHPO 4 ⅐2H 2 O, before the rise of life-mediated apatite deposition (2). Because ...

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Section: Phosphorus In the Origin Of Lifementioning

confidence: 99%

Rethinking early Earth phosphorus geochemistry

Pasek

2008

Proc. Natl. Acad. Sci. U.S.A.

235

209

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“…Another example in which surface density may have a role in condensation reactions is that reported by Ibanez et al (1970), involving condensation of mononucleotides in the presence of montmorillonite in an aqueous medium. Though no data were given concerning the adsorption reactions, the mean density of the adsorbed molecules was relatively low since the total amounts of the mononucleotide and the clay were 25 ~M and 35 mg, respectively.…”

Section: Reevaluationmentioning

confidence: 95%

The possible role of solid surface area in condensation reactions during chemical evolution: Reevaluation

1976

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Published data on adsorption and condensation of amino acids, purine and pyrimidine bases, sugars, nucleosides, and nucleotides are analyzed in connection with Bernal's hypothesis that clays and other minerals may have provided the most likely surface for adsorption and condensation of these molecules in prebiotic times. Using surface concentration and reaction rate as the main criteria for the feasibility of condensation reactions, four types of prebiotic environments were analyzed: (1) an ocean-sediment system, (2) a dehydrated lagoon bed produced by evaporation, (3) the surface of a frozen sediment, and (4) a fluctuating system where hydration (rainstorms, tidal variations, flooding) and dehysration (evaporation) take place in a cyclic manner. With the possible exception of nucleotides, low adsorption of organomonomers on sediment surfaces of a prebiotic ocean (pH 8) is expected, and significant condensation is considered unlikely. In dehydrated and frozen systems, high surface concentrations are probable and condensation is more likely. In fluctuating environments, condensation rates will be enhanced and the size distribution of the oligomers formed during dehydration may be influenced by a "redistribution mechanism" in which adsorbed oligomers and monomers are desorbed and redistributed on the solid surface during the next hydration-dehydration cycle.

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“…It dimerizes to dicyanamide CHEMICAL MARKERS 113 NH II (cyanoguanidine) ( H2NCNHCN ) on heating in the dry state or in solution and is hydrolyzed to urea in aqueous acid and base (Prager et al, 1910). It may have effected the condensation of amino acids to oligopeptides or nucleotides to oligonucleotides on the primitive earth (Ibanez et al, 1971). …”

Section: Cyanamide (Nh2cn)mentioning

confidence: 98%

Marine Hydrothermal Systems and the Origin of Life

Holm¹

1992

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Possible Prebiotic Condensation of Mononucleotides by Cyanamide

Abstract: The condensation of mononucleotides has been carried out in aqueous solution at neutral pH in the presence of cyanamide. Oligodeoxyribonucleotides up to five units have been formed when montmorillonite was present.

Cited by 86 publications

References 18 publications

Rethinking early Earth phosphorus geochemistry

Rethinking early Earth phosphorus geochemistry

The possible role of solid surface area in condensation reactions during chemical evolution: Reevaluation

Marine Hydrothermal Systems and the Origin of Life

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