Isolation of pyrimidine isostichs from chick erythrocyte DNA

[Isolation of oligonucleotides from partial hydrolysates of DNA using template chromatography]

Purine oligonucleotides are adsorbed at 0 degree C on poly(vinyl alcohol)-p(dC)n-DEAE-cellulose, and pyrimidine oligonucleotides on oligo(guanylic acid) gel according to the base-pairing mechanism, if their sequences contain at least three or more homologous, consecutive guanylic or cytidylic moieties. By increasing the temperature all base-paired oligonucleotides are desorbed. With this template chromatography mixtures of defined purine- or pyrimidine oligonucleotides could be isolated from fractionated partial hydrolyzates of herring sperm DNA. Afterwards these mixtures are rechromatographed on QAE-Sephadex and/or Nucleosil C18. Using this approach oligonucleotides up to nine monomer units can be isolated either as single substances or as mixtures with defined composition on a preparative scale, which would be not possible with the already existing separation procedures when partial hydrolyzates of herring sperm DNA as starting material are used. Purity and sequence of the isolated oligonucleotides are determined by the "fingerprint" method.

[Preparative isolation of hexa-, hepta-, octa-, nona- and decapyrimidine oligonucleotides from hydrolysates of depurinated herring sperm DNA]

The pyrimidine oligonucleotides (dT)5; (dT)6 and the mixtures of sequence isomers (dC, dT5); (dC2, dT5); (dC3, dT4); (dC4, dT3); (dC4, dT4); (dC3, dT5); (dC2, dT6); (dC4, dT5); (dC3, dT6); (dC2, dT7); (dC5, dT5); (dC4, dT6) and (dC3, dT7) with or without terminal phosphate groups have been isolated on a preparative scale from hydrolysates of depurinated herring sperm DNA by the following procedure. Herring sperm DNA (1 kg) is chemically depurinated and partially hydrolysed to a mixture of pyrimidine nucleotides. The partial hydrolysate is first separated into a low- and a high-molecular-weight pyrimidine nucleotide mixture by column chromatography on DEAE-cellulose. The mixture of high-molecular-weight pyrimidine nucleotides is subsequently fractionated on QAE-Sephadex. Impurities which are not fully removed by column chromatography are separated by paper chromatography. The compositions of the mixtures of sequence isomers are determined from the data of column, paper and homochromatography; from absorption characteristics and by enzymatic degradation.