Experimental Results

We investigated two types of reactions:

(1) Abiogenic synthesis of nucleotides from mixtures of nucleoside + inorganic phosphate;

(2) Abiogenic synthesis of dipeptides from mixtures of simple amino acids.

The reaction mixture in the form of a solid film contains nucleoside and dihydrogen phosphate or two different amino acids. Seven different nucleosides (thymidine, cytidine, uracil, adenosine or deoxyadenosine, guanosine or deoxyguanosine) and inorganic phosphate and four mixtures of aromatic (tyrosine or triptophan) and aliphatic (glycin or alanine) amino acids are investigated. Mixtures were prepared by air drying of aqueous solutions and irradiated by different sources of energy:

(3) were installed on the surface of biosputnik in outstanding container (OC) when they were exposed to the action of all spectra of the open space energy sources during the entire time of flight - 327 hours (24.12.1996 - 07.01.1997).

As a result of VUV irradiation of the solid mixture of nucleoside and inorganic phosphate the natural monophosphates of corresponding nucleosides were found [18,19]. The main products were nucleoside-5'-monophosphates and some amount of by-products (2'- and 3'-mono-phosphates, 2'3'- and 3'5'-cyclomonophosphates). The yields of products were small, less than a few per cent, however the effectiveness of the abiogenic synthesis on VUV irradiation is higher than on UV-radiation and heat. When investigated films were irradiated with protons, the full mixture of nucleotides also was found. The maximal summary yield of nucleotides was 9.43% (under action of 2 MeV protons). The main product was 5'AMP (3.19%) as under action of VUV. Preferable 5'-monophosphate formation is indicative of more advantageous spatial position of 5'hydroxyl group in carbohydrate residue in comparison with 2' and 3' hydroxyl groups. The 2'3'-cyclomonophosphate has been formed in solid films as well. It is interesting to note the yield of 2'3'cAMP has values more than those of 2'- and 3'-monophosphates. In our previous papers we had proposed that interaction between all three nucleotides exists under VUV radiation [18,19] and g-radiation [20]. Kinetic analyses carried out in a recent paper [21] suggested that 2'3'-cyclomonophosphate formation arose from 3'- or 2'-nucleoside derivatives. In this work it was also shown that the 5'-OH site is inherently favored over the 3'- or 2'-OH in phosphorylation. We can see that 5'-nucleotides are predominantly formed under action of all investigated sources of energy as well as in open space energy. Other nucleotides (2'and 3') and cyclic nucleotides, such as 2'3'cAMP and 2'3'cCMP also have been found in the all investigated films.

The films containing a mixture of amino acids yielded various dipeptides after they were exposed to VUV-radiation and protons [22,23], Polymerization is an essential step in prebiological evolution and we have shown that this process probably could take place even at early stages of Solar System formation, before planet accretion, on surface of small bodies.

It was important to test how far the process of chemical evolution could take place on the surface of space bodies under the action of all energy sources of open space. In space flight experiment on board the "BION-11" satellite the solid films from mixtures of different nucleosides and inorganic phosphate are exposed to space conditions. The abiogenic synthesis of such nucleotides as 5'-, 2'- and 3'- monophosphates of thymidine, cytidine, adenosine and deoxyadenosine is observed. The cyclomonophosphates are synthesized also [24],

The main products of the reactions in all experiments were 5'monophosphates of corresponding nucleosides as in the laboratory investigations.

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