Spectrometric Study of the Oligodeoxyribonucleotide Protonation in Aqueous Solution

摘要

UV absorption spectra and circular dichroism spectra of aqueous solutions of cytosin- and thymine-containing single-stranded Oligodeoxyribonucleotide 5'-CCTTTCCTTTTCCTTTCC-3'(ckit4) were measured at various pH in the range 3.3-8.9. The chemometric analysis of the multiinstrumental data matrix was carried out. The diagrams of relative contents of complex forms of the DNA molecule absorbing in the studied wavelength range (220-320 nm) were constructed by the ALS-MCR soft simulation procedure without initial postulation of their chemical compositions. The model of equilibrium complex formation describing observed changes in the spectra depending on the solution acidity was developed on the basis of the matrix method. Intrinsic protonation constants of the oligonucleotide ckit4 were calculated. The formation of intramolecular complexes between cytosine C.C+ bases in the studied DNA molecule is of a cooperative nature, and their subsequent protonation is an anticooperative process.