Synthesis of Sugars in Potentially Prebiotic Conditions

NATURE. VOL. 216. NOVEMBER 4. 1967 455

a~tached to .carbon. Co-ordination of the oxygens with "Akerlof, G. C.• and Mitchell, P. W. D., Final Report, NASA Oontract divalent catIOns (2) would greatly enhance this effect NASr·88 (1963). 11 Walker, J. F., Formaldehl/de, 53 (Reinhold Publishing Corporation, New which would explain in part the greater efficacy of York, 1964). divalent oxides as catalysts_ It should be noted that the to Franzen, H., and Hauck, L., J. Pralet. Ohem., 91, 261 (1915). "Staudinger, H., Signer, R., and Schweitzer. 0., Bet'. Deulsch. Ohem. Gea., 64, 898 (1931).

(2) Synthesis of Sugars in Potentially Prebiotic Conditions microcrystal~ine clay minerals usually have alkaline earths, alkah metals and protons adsorbed as cations on THE formation of sugars from formaldehyde has been li their.surfaces • ~ra.nzen and Hauckzo have reported that studied extensivelyl, but the reaction has usually been alkalme earth catIOns form salts with aqueous formalde carried out in conditions too extreme t.o have existed hyde, and although Staudinger et al.1l have shown that on the primitive Earth. The claim that relatively pure there is no definite composition to these materials, they ribose can be obtained by boiling formaldehyde with a are probably co-ordination complexes of the metals with suspension of calcium carbonate2 led us to investigate the water, hydroxide ions, and a variety of chain lengths of catalytic activity of "carbonate-apatite". Hydroxy partially polymerized formaldehyde_ apatite, a very common phosphate mineral, is inactive; The polyvalent cations, which are Lewis acids also we argued that if carbon dioxide was abundant at any co-ordinate with the carbonyl oxygen atom of' non stage in the evolution of the ocean, carbonate incor hydrated formaldehyde, rendering the carbon atom much poration into apatite must have been extensive. more subject to nucleophilic attack. It can further be A slurry of "carbonate-apatite" prepared freshly by expected that the polyvalent cations would also stabilize the method of Hayek et al.·, was found to have a pH of the enolate anions of the hydroxy aldehydes and ketones 8·5. On boiling with 0·5 molar formaldehyde, it gave (3). yields of up to 40 per cent of sugars. There was an initial induction period of several hours during which no sugars could be detected, then glycolaldehyde, trioses, tetroses, pentoses and hexoses appeared successively. Sugars were separated by chromatography in butanol-acetic acid water (4 : 1 : 5, upper phase) and in acetic acid-pyridine water (7: 3 : 2) and estimated using the acid aniline phthalate sprayl. Pentoses are present in maximal amount after about 12 hand hexoses after about 24 h. In this work, it has been shown that a dilute (10-Z When boiling was continued for longer periods the molar) solution of formaldehyde can be condensed to a solution darkened and the sugars gradually disappeared; mixture of sugars in conditions designed to simulate a the hexoses persisted longest. We obtained similar results primordial hydrothermal spring. An alkaline medium when we used calcium carbonate as a catalyst, but the is unnecessary for this condensation to take place. whole sequence of reactions proceeded more slowly. The reaction takes place at mildly acid and neutral pH. When this experiment was repeated using more dilute The basic sites on the crystal lattice of the alumina and formaldehyde, we could still detect sugars from 0·01 molar aluminosilicates probably serve to remove protons from solution but not from 0·001 molar. The minimum detect the formaldehyde and various intermediates absorbed on able yield in the latter experiment was 1-2 per cent. In the mineral surfaces, thereby providing the necessary these experiments, we used formaldehyde labelled with reactant molecules. carbon-l4 to obtain greater sensitivity in our analyses. A reasonable rationale for the production of hexoses in The experiment was discontinued after 14 days. These 10-1 molar solution of formaldehyde and not in a 0·33 results are similar to those reported by Gabel and Pon molar solution is that in dilute solution an individual namperuma4, who used a suspension of Al.Os as catalyst. reaction intermediate will be absorbed for a longer time We do not believe that the formose reaction as we and on the mineral surface. Conversely, in a more concen others have carried it out is a plausible model for the pre trated solution, the reaction intermediate is more quickly biotic accumulation of sugars. First, it requires concen displaced from the mineral surface by the other solute trated formaldehyde solutions and, second, the sugars molecules. It can be expected that the longer any given formed are decomposed quite quickly. If formaldehyde is reactant remains on the active surface of the ca.talyst the the prebiotic precursor of ribose, some method of stabil greater are its chances of undergoing further reactions to izing the sugars is essential. The formation of ribosides form products of higher molecular weight. of the natural bases-for example, adenin&-is one pos sibility, but attempts to bring about this condensation Received August 29. 1967. have not been successful. Instead, rather unstable 5 adducts were formed • 1 Butlerow. A., Annalen, 120, 296 (1861). • Loew, 0., J. Prakt. Ohem., 34, 51 (1886). The formation of sugars in plausible conditions and their • Loew, 0., Ber. Deutsck. Ohem. Gel., 20, 144 (1887). incorporation into nucleosides have not been achieved. , Loew, 0., Ber. Deutsch. Ohem. (hs., 22, 475 (1889). Until the problem is solved or by-passed it remains a 'Euler, H., snd Euler, A., Ber. Deutsch. Ohem. Ge •. , 39, 50 (1906). weakness in theories of abiotic nucleic-acid synthesis. • Langenbeck, W., Nalurwi8ssmckolten, 30, 80 (1942). , Mayer, R., snd Jaschke, L., Annalen, 836, 145 (1960). C. REID • Mayer, R., snd Jaschke, L., Anqew. Ohem., 72, 685 (1960). L. E. ORGEL • Miller, S, L., and Urey, H. C., Science, 130, 245 (1959). •• Palm, C., snd Calvin, M., J. Amer. Chem. Soo., 84, 2115 (1962). The Salk Institute for Biological Studies, H Ponnamperwna, C., and Flores, J., RtJdiat. Bu., SIS, 229 (1965). San Diego, California. .. Ponnamperuma, C., In Fox, S. W., The Oriqim of Prebiological SI/.tem. and of Their MoIeculM Matrkes, 221 (Academic Press, New York. 1966). " Horowitz., N. H., and Miller, S. L., Fort8ckr. Ohem. Org. NalurstojJe, 20, Received October 6, 1967. 423 (1962). " Abelson, P. Hoo Proo. US Nat. Acad. Sci., 65, 1365 (1966). 1 Prell, Eoo and Ruckert, R., Ann. .. 841, 121 (1961) and references therein. .. Grim, R. E., Olal/ Mineralogy (McGraw-Hili Book Company, Inc., New • Mayer, R ., and Jaschke, L., Ann., 88lI, 145 (1960) • York, 1953). • Hayek, E .• Konetschny, H., and Schnell, E., Angew. Ohem. Intern. Edit., 6, it Elliot, D. C., in Dawson, R. M. C., Data for Biochemical Research, 238 669 (1966). (Oxford University Press, London, 1959). , Gabel, N., and Ponnamperwna, C., Nalure, 216, 453 (1967). J. A., Bioohem. Biophl/B. Bu. Oommun., 8, 418 (1961). • Reid, C., Orgel, I,. E., and Ponnamperuma, C., Nalure (in the press).