Oligo-2 -5 -adenylates

Imidazolides of adenylic acid (ImpA) or uridylic acid (ImpU) are polycondensed to oligonucleotides by means of Zn2+ ions. 1673 The resulting phosphordiester bond was found to be of the 2, 5 type. In the reaction of nucleoside 5 -phosphoric acid methyl ester with ImpA in the presence of MgC, 2, 5 -dinucleotides are formed six to nine times more frequently than the corresponding 3, 5 compounds. 63 Polycondensations of ImpA in aqueous solution in the presence of various divalent metal ions lead to short oligo-adenylic acids (pA) (n = 1—5) mainly with 2, 5 -intemucleotide linkages. With Pb2+, for example, the total yield of oligomers was as high as 57%. 1683 1693... 

Adenosine 5 -phosphorimidazolidate condenses in aqueous solution in the presence of divalent metal ions to form oligo(adenylic acid). Using divalent lead ions, as much as 57% condensation to oligo(A) has been reported studies on the di-and tri-nucleotide with RNase Tg show the internucleotide bonds to be mainly 2 ->5 -linked. The metals most efficient in catalysing condensation occupy an intermediate position in the classification as hard and soft acids and bases, and it is thought that they may co-ordinate to both base and phosphate. 

In conclusion, our results are indicative of a new pathway involving 2, 5 -oligo-adenylates in cell metabolism. In fact, such compounds can regulate ADP-ribosylation of proteins, which in turn may be crucial for the induction of the antiviral state of cells treated with interferon. 

Kinoshita, Imoto et al,9 12 polymerized 3-(9-adenyl)-2-hydroxypropyldihydrogen-phosphate, / (oligo-9-AP), 3-(3-adenyl)-2-hydroxypropyldihydrogenphosphate,... 

As an oligo(A)-primed, terminal adenylate transferase of cellular origin was found in tight association with the same membranes the replication complex is bound to, the longer poly(A) stretches were thought to result from either a mechanism of "slippage" or by end addition of adenylate residues (89). 

The isolation of mRNA also became possible during the years of the decade. The discovery that a large proportion of mRNA species carried polymers of adenylate at their 3 -OH ends enabled the design of affinity chromatography supports such as oligo-dT cellulose and poly-U Sepharose which, because of their complementarity with the poly-A tails of the mRNA, could be employed to purify them from total RNA. These same poly-A tails made the purified mRNAs ideal substrates for reverse transcriptase. Oligomers of deoxythymidine (dT) could hydrogen bond to the poly-A and provide a primer for the initiation of transcription of a cDNA. 

A, C, G and U—adenylate, cytidylate, guanylate and uridylate residues in oligo and polynucleotides GMPPCP—5 guanylyl-methylene-diphosphonate acPhe-tRNA—acetyl Phe-tRNA acdiPhe-tRNA—acetyl PhePhe-tRNA. 

Alternative routes for the prebiotic synthesis of oligo- and polypeptides in aqueous systems, at relatively low temperatures, may well have involved activated monomers like oc-amino nitriles, a-amino amides or amino acyl adenylates. Interesting results were obtained earlier with the first two types of compounds in our laboratory and other laboratories. More recently the amino acyl adenylates, in the presence of montmorillonite and at pH... 

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