Showing papers by "Leslie E. Orgel published in 1978"
TL;DR: In this paper, the synthesis of isomeric dinucleotides using ImpU with MepU, MepC, ImpA and MepG in aqueous solution yields mixtures of (2'−5') linked compound is 6-9 times more abundant than the (3' −5')-linked compound.
157 citations
TL;DR: The results suggest that, on the primitive Earth, pyrimidine nucleotides could most easily have been incorporated into polymers as constituents of short oligomers, which contained one or more purine nucleotide.
Abstract: We have studied a number of condensation reactions involving ImpU, ImpT, ImpC, ImpA, ImpG, ImpUgG and ImpCpA as activated nucleotide donors and a variety of homo- and hetero-polynucleotides as templates. We did not not obtain any evidence of a template effect with ImpU and ImpT, but observed some condensation of ImpC with GpG on appropriate templates. ImpA and ImpG take part in a number of more or less efficient template-directed reactions, as do ImpUpG and ImpCpA. Our results suggest that, on the primitive Earth, pyrimidine nucleotides could most easily have been incorporated into polymers as constituents of short oligomers, which contained one or more purine nucleotide. The linkage of the product depends strongly on the nature of the substrates; the percentage of the natural 3'-5'-linkage was, in some cases, less than 10% and, in others, as high as 70%. Wobble-pairing was often very effective in promoting condensations, suggesting that transition mutations would have been very frequent in prebiotic polynucleotide replication.
50 citations
TL;DR: The aminolysis of 2′(3′)-O-(glycyl)-adenosine-5′-(O-methylphosphate) by free glycine is relatively inefficient, but serine reacts 20 times more rapidly and yields up to 50% of N-glycylserine.
Abstract: We have synthesized 2′(3′)-O-(glycyl)-adenosine-5′-(O-methylphos-phate), an analogue of the 3′-terminus of aminoacylated tRNA. A 0.4M solution of this compound maintained at pH 8.2, yields 5.5% of diglycine and 11.5% of diketopiperazine, in addition to the hydrolysis products glycine and adenosine-5′-(O-methylphosphate). Under the same conditions, glycine ethyl ester reacts much more slowly, but ultimately gives similar yields of diglycine and diketopiperazine. The aminolysis of 2′(3′)-O-(glycyl)-adenosine-5′-(O-methylphosphate) by free glycine is relatively inefficient, but serine reacts 20 times more rapidly and yields up to 50% of N-glycylserine. The prebiotic significance of these reactions is discussed.
41 citations
TL;DR: Amino acids are activated by reaction with adenosine 5′-phosphorimidazolide in aqueous imidazole buffers by an analogue of the 3′-terminus of t-RNA, and analogous reactions occured with several other amino acids, including a number that have functional side-chains.
Abstract: Amino acids are activated by reaction with adenosine 5′-phosphorimidazolide in aqueous imidazole buffers. If adenosine 5′-(O-methylphosphate), an analogue of the 3′-terminus of t-RNA is present, 2′(3′)-O-aminoacyladenosine 5′-(O-methylphosphate) is formed. Fifteen percent of this compound accumulated at pH 5.8, but less was formed at higher pHs. The highest efficiency of utilization of ImpA attained in our experiments was about 24%. Analogous reactions occured with several other amino acids, including a number that have functional side-chains.
25 citations
TL;DR: Imidazolides of din nucleotides such as ImpApA can be formed from the corresponding dinucleotides in a two-stage process, which gives up to 15% yields under potentially prebiotic conditions.
Abstract: Imidazolides of dinucleotides such as ImpApA can be formed from the corresponding dinucleotides in a two-stage process, which gives up to 15% yields under potentially prebiotic conditions. First a solution of the dinucleotide and sodium trimetaphosphate is dried out at constant temperature and humidity. This produces polyphosphates such as pnApA in excellent yield (⩾80%). The products are dissolved in water, imidazole is added, and the solution is dried out again. This yields the 5′-phosphorimidazolides.
12 citations
TL;DR: This work suggests that this synthesis of organic pyrophosphates such as UppA and NAD may have occured concurrently with oligonucleotide formation.
Abstract: Organic pyrophosphates such as UppA and NAD are formed when a solution containing a nucleotide, a nucleoside 5'-polyphosphate, Mg2+ and imidazole are allowed to dry out. We suggest that this synthesis may have occured concurrently with oligonucleotide formation.
8 citations
01 Jan 1978