Studies on the nucleotide arrangement in DNA. Estimation of sequence isomers in pyrimidine deoxyribo-oligonucleotides

The population of pyrimidine deoxyribo-oligonucleotides obtained from DNA may be separated, first, into fractions comprising identical lengths (isotichs) and, subsequently, into the individual components of an isostich fraction varying in the cytidylic and thymidylic acid composition. At a third level of analysis the proportion of components exhibiting the same composition but different sequence may be determined. Selective removal of cytosine and the subsequent analysis for characteristic thymidine derivatives released during an acid-catalyzed beta-elimination reaction allowed estimation of the relative proportion of sequence isomers for pyrimidine isostichs of length two to five.