High-performance liquid chromatography of the photoproducts of nucleic acid components. III. Detection of the secondary structure differences in sequence isomeric self-complementary oligonucleotides.

Reversed-phase high-performance liquid chromatography (RP-HPLC) was used to detect differences in the secondary structures of two self-complementary oligodeoxyribonucleotides. The [d(CCTTTAAAGG)]2 duplex assumes an ordinary B-conformation in aqueous solution, while [d(GGAAATTTCC)]2 is known to contain in its central part a stretch of a more rigid B'-form conformation with significantly lowered fluctuational mobility of base pairs. The latter factor causes a marked difference in the amounts of thymine cyclobutane photodimers formed under UV irradiation of corresponding duplexes as revealed by chromatography of two single-stranded oligonucleotides. Increasing the temperature below the duplex melting temperature (stimulation of the B'-B structural transition) results in an increase in photodimer formation that was inhibited in the B'-form. Thus, we demonstrate the usefulness of RP-HPLC for duplex DNA structural studies.