Chemical evolution 40. clay-mediated oxidation of diaminomaleonitrile

Huang

Hagan

1988

Reaction of diiminosuccinonitrile (DISN) with 3'-AMP in the presence of alkali- and alkaline earth-montmorillonites results in the formation of 2',3'-cAMP in aqueous solution. Little or no 2', 3'-cAMP is produced when metal ion concentrations equivalent to that of the metal ion associated with the homoionic clays are used instead of mobntmorillionite. Yields comparable to those obtained with DISN are obtained when diaminomaleonitrile (DAMN) is used in place of DISN as the condensing agent. DAMN, a compound which is more stable than DISN in aqueous solution, is oxidized to DISN on the surface of the clay by Fe+3 in the clay lattice. DISN, the true condensing agent, is thus generated in the presence of the bound 3'-AMP on the montmorillonite surface. The montmorillonite catalyzes the DISN-mediated formation of 2', 3'-cAMP and this product, which binds much less strongly than does the 3'-AMP, is desorbed from the clay surface. This research established that the montmorillonite performs four different functions in its role as catalyst: (1) Binding one of the substrate molecules (3'-AMP) (2) Activating the second substrate (DAMN) (3) Catalyzing the formation of 2', 3'-cAMP (4) Releasing the reaction product so another substrate molecules can bind to the montmorillonite.

Section: Resultssupporting

confidence: 77%

Montmorillonite: A multifunctional mineral catalyst for the prebiological formation of phosphate esters

Huang

Hagan

1988

“…DISN is a likely product of HCN oligomerization on the primitive Earth [ 14]. It effects the formation of the phosphodiester linkage in neutral aqueous solution in a reaction that is catalyzed by divalent metal ions.…”

Section: Disn and Prebiotic Synthesismentioning

confidence: 99%

“…We were prompted to reinvestigate the role of HCN derivatives as prebiotic condensing agents by the observation that the oxidation of DAMN to diiminosuccinonitrile (DISN) proceeds readily in solution and on clay mineral surfaces [13,14]. The rapid reaction of DISN with nucleophiles [15] suggests that its reaction with phosphate and carboxylate derivatives would yield 1 and 3 respectively (Scheme I), imino analogs of mixed anhydrides, compounds that would condense readily with amino or hydroxyl groups to give phosphodiester (_2), peptide (4_) and pyrophosphate links.…”

Section: Introductionmentioning

confidence: 99%

The investigation of the hcn derivative diiminosuccinonitrile as a prebiotic condensing agent. The formation of phosphate esters

Yanagawa

Dudgeon

et al. 1984

Self Cite

Diiminosuccinonitrile (DISN) is formed readily by the Fe3+ oxidation of diaminomaleonitrile, a tetramer of HCN. DISN effects the phosphorylation of uridine in 13% yield to a mixture of the isomers of UMP when the reaction is performed in dimethylformamide solution. A 4% yield of the UMP isomers is obtained in neutral aqueous solution using 2 times the DISN concentration and 7 times the phosphate concentration used in DMF. DISN did not effect the conversion of adenosine to AMP or 5'-AMP to 5'-ADP in aqueous solution. The cyclization of 3'-AMP and 3'-UMP to the corresponding 2'-3'-cyclic phosphates proceeds in yields as high as 40-50% at 60 degrees C in pH 6 aqueous solutions in the presence of divalent metal ions. Lower yields of the cyclic phosphate are observed when 2'-AMP is the starting material. Substitution of acetate buffer for imidazole buffer results in a decrease in the yield of cyclic phosphate, the extent of which depends on the metal ion used in the reaction. No 3'5'-cyclic AMP was detected as a reaction product with either 5'-AMP or 3'-AMP as the starting material except for a 2.4% yield from 3'-AMP in the presence of Zn2+. BrCN effects the conversion of 3'-AMP to the 2'-3'-cyclic AMP in 37-65% yield depending on the divalent cation used as catalyst. A mechanism has been proposed for these cyclization reactions and their potential significance to the prebiotic synthesis of ribonucleic acid derivatives is discussed.

“…Previous work in this laboratory established that the Fe 3 +, which occurs as an isomorphic substituent in the lattice of montmorillonite 22A, oxidizes DAMN to DISN (Ferris et al, 1982). It was determined from the Fe 3 + content of the clay mineral that 1.74 moles of Fe z + are formed per mole of D A M N oxidized.…”

Section: B Montmorillonite-mediated Oxidation Of Diaminomaleonitrilementioning

confidence: 99%

The adsorption and reaction of adenine nucleotides on montmorillonite

Hagan

1986

The binding of AMP to Zn(2+)-montmorillonite was investigated in the presence of buffers and salts. Good's buffers, piperazine-N,N'-bis(2-ethanesulfonate) [PIPES] and morpholine-N-2-ethanesulfonate [MES], perturbed the exchangeable cations to a lesser extent (only 9% of Zn2+ displaced by 0.2 M buffer) than was observed with imidazole and lutidine buffers or NaCl and KCl salts (up to 80% of Zn2+ displaced). AMP adsorption isotherms measured in the presence of 0.2 M PIPES, MES, or Na2SO4 exhibited normal Langmuir-type behavior. The adsorption coefficient, KL, is 3-fold greater in the presence of HEPES or PIPES than it is in the absence of buffers. Basal spacings measured by X-ray diffraction for Zn(2+)-montmorillonite are 13 and 15 angstroms in the presence of PIPES, while a value of 12.8 angstroms was determined in the absence of PIPES. These data are interpreted in a model in which the adsorption of AMP is mediated by a Zn2+ complex of PIPES in different orientations in the interlamellar region of the montmorillonite. The type of exchangeable cation does not affect the ability of the lattice-bound Fe3+ in the montmorillonite to oxidize diaminomaleonitrile (DAMN). Exchangeable Cu2+ oxidizes DAMN, but exchangeable Fe3+ is nearly ineffective as an oxidant. The addition of DISN to 3'-AMP bound to Zn(2+)-montmorillonite in the presence of 0.2 M PIPES resulted in a higher yield of 2',3'-cAMP than is observed with a comparable concentration of Zn2+, a result which inplicates surface catalysis by the montmorillonite.