Non-enzymatic synthesis of the coenzymes,uridine diphosphate glucose and cytidine diphosphate choline,and other phosphorylated metabolic intermediates

The synthesis of uridine diphosphate glucose (UDPG), cytidine diphosphate choline (CDP-choline), glucose-1-phosphate (G1P) and glucose-6-phosphate (G6P) has been accomplished under simulated prebiotic conditions using urea and cyanamide, two condensing agents considered to have been present on the primitive Earth. The synthesis of UDPG was carried out by reacting G1P and UTP at 70 °C for 24 hours in the presence of the condensing agents in an aqueous medium. CDP-choline was obtained under the same conditions by reacting choline phosphate and CTP. G1P and G6P were synthesized from glucose and inorganic phosphate at 70 °C for 16 hours. Separation and identification of the reaction products have been performed by paper chromatography, thin layer chromatography, enzymatic analysis and ion pair reverse phase high performance liquid chromatography. These results suggest that metabolic intermediates could have been synthesized on the primitive Earth from simple precursors by means of prebiotic condensing agents.     

Effect of variation of retinal polyene side-chain length on formation and function of bacteriorhodopsin analogue pigments

The effect of the length of the retinal polyene side chain on bacterioopsin pigment formation and function has been investigated with two series of synthetic retinal analogues. Cyclohexyl derivatives with polyene chains one carbon longer and one or more carbons shorter than retinal and linear polyenes with no ring have been synthesized and characterized. Compounds of six carbons or less in the polyene chain form pigments very poorly or not at all with bacterioopsin. Compounds containing at least seven carbons in the chain are found to form reasonably stable bacterioopsin pigments that show a small shift in absorbance on irradiation. However, photocycling and proton photorelease are not detected. The analogue with nine carbons in the polyene chain (one less than retinal) forms a stable pigment with an M-type intermediate but demonstrates reduced amounts of photocycling and light-activated proton release. The analogue with a polyene chain identical with that of retinal, but containing no ring, forms a pigment that shows both an efficient light-activated proton photocycle and release. The pigment containing the chromophore with the polyene chain one carbon longer than retinal is likewise fully active. We thus conclude that the length of the polyene chain must be at least 9 carbons for the formation of a stable pigment that photocycles and must be 10 carbons for both the photocycle and light-activated proton release to have a high quantum efficiency.     

Primary Sources of Phosphorus and Phosphates in Chemical Evolution

In this work we consider the role of phosphorus in chemical evolution from an interdisciplinary approach. First we briefly review the presence of this element in different cosmic sites, such as massive stellar cores, circumstellar and interstellar clouds, meteorites, lunar and Martian samples, interplanetary dust particles, cometary dust and planetary atmospheres. Thus we illustrate the fact that phosphorus seems to be, at the same time, scarce and ubiquitous in the solar system. Afterwards, by comparing the phosphorus content of our planet's main reservoirs with the amount of cometary and meteoritic matter captured by the primitive Earth, we conclude that comets may have provided a primary source for phosphorus compounds of prebiotic interest. Finally, we make a number of proposals aimed to gain observational supporting evidence to the above conclusion and other suggestions made in the article.