A possible prebiotic phosphorylation method has been investigated in which formamide served as the reaction medium. Nucleotides and nucleotide derivatives were formed when nucleosides were allowed to react with different orthophosphate, hydrogen phosphate or dihydrogen phosphate salts or with different condensed phosphate salts. The reaction products obtained from the phosphorylation of adenosine were 2'3' and 5'-AMPs, 2',5' and 3',5'-ADPs and 2',3'-cyclic AMP. The extent of phosphorylation in formamide exceeded 50% under favorable conditions after 15 days at 70 degrees. The acidic dihydrogen phosphates and condensed hydrogen phosphates proved to be the best phosphorylating agents. The presence of water in the medium decreased the yield of nucleotide derivatives, but some phosphorylation of adenosine was detected using dihydrogen phosphate in formamide containing water. The phosphorylation reactions were also observed for deoxynucleosides. Little decompression of the nucleosides was detected during the reaction time needed to form nucleotide derivatives. The facility with which phosphorylation takes place in formamide under very mild conditions may justify further studies both of prebiotic phosphorylation and synthetic phosphorylation using this solvent.
Informed science educators who are responsible for undergraduate laboratory programs strive to improve the effectiveness of learning in the laboratory. Guided-inquiry learning in the laboratory is one reasonable alternative (among others described here) to the verification approach to learning. Guided-inquiry learning offers students the opportunity to learn for themselves in a controlled laboratory environment where the instructor can handle the outcome and help guide students who are experiencing difficulty. Guided-inquiry experiments in organic chemistry have merit because they may help to improve understanding while increasing student interest. This paper presents the advantages and disadvantages of guided-inquiry experiments in organic chemistry. Several different types of guided-inquiry experiments in organic chemistry are summarized, together with the rationale for converting verification laboratory procedures to guided-inquiry experiments. Examples are given for enhancing guided-inquiry experiments to make the outcomes less predictable.
Nucleosides or deoxynucleosides were converted to a number of phosphorylated nucleotide and deoxynucleotide derivatives by ammonium of alkali dihydrogen phosphates in formamide. Conversions were smaller and slower at room temperature and greater and faster at elevated temperatures. Nucleotides afforded product mixtures to those obtained for nucleosides under the same conditions, indicating the occurrence of transphosphorylation processes. Products of the reaction at elevated temperatures were cyclic nucleotides, nucleoside monophosphates, nucleoside diphosphates and cyclic nucleotide phosphates. The relative amounts of products formed were quite temperature dependent. Cyclic nucleotides were found to be in greatest abundance for reactions run at 125 degree or above. Relative yields of 2',3' and 5' nucleotides and 3' and 5' deoxynucleotides from several experiments are reported. 5'Monophosphates were generally found to be present in larger quantities than 2' or 3' monophosphates. 2'-Deoxyadenosine showed a preference for phosphorylation at the 3' position. Conclusion reached from mechanistic studies are that the phosphorylations are a series of equilibrium reactions, with cyclic nucleotides being formed irreversibly.
Abstract. An objective of this work is to elucidate the mechanism of phosphorylation of nucleosides in amide solvents and in urea. A second objective is to assess the importance of phosphorylation and dephosphorylation of nucleotide derivatives in amide environments. Although the most complex amide studied here was N-methylacetamide, inferences are made on the importance of dephosphorylation for nucleotides in oligopeptide environments.Phosphorylations in amide solvents and in urea are suggested to proceed through monomeric metaphosphate, which was first postulated as a reaction intermediate thirty years ago (Butcher and Westheimer, 1955). Phosphorylation of nucleosides and nucleotides and dephosphorylation of nucleotide derivatives have been studied in formamide, N-methylformamide, urea and N-methylacetamide. Hydrated forms of 5'-ADP and 5'ATP are unstable in hot amide solvents and in urea. They decompose to a mixture of adenosine and its phosphorylated derivatives. The rate of decomposition is much slower in N-methylacetamide than in formamide or urea. Experiments designed to prepare oligonucleotides in the presence of oligopeptides have been reported (White, 1983). According to the present study, it is not unreasonable to expect that nucleotide derivatives can be condensed with nucleosides to form oligonucleotides in a peptide environment. However, nucleotide monomers such as 5'-ATP, 5'-ADP or 5'AMP will suffer isomerization or decomposition during condensation use of activated phosphate derivatives is preferable.Monomeric metaphosphate has not been isolated or characterized in amide solvents. It is proposed here as a reaction intermediate, probably in a complexed form with the amide.
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