[Complementary addressed modification of a hairpin-shaped model oligodeoxyribonucleotide].

A hairpin-shaped oligodeoxyribonucleotide d(pTTGGCACGAGCAGCCAA) (I) was alkylated with the reagent d(TTGGG) greater than UCHRCl (RCl = -C6H5-N(CH3)-CH2-CH2Cl) complementary to the hairpin's stem. Thermodynamic parameters for the hairpin structure estimated from melting curves were: delta Hh = -125 +/- 17 kJ/mol, delta Sh = -380 +/- 84 J/mol.K; and for the reagent - target complex delta Hpx = -155 +/- 8 kJ/mol, delta Spx = -427 +/- 21 J/mol.K. Effective constants of association Kx of the oligonucleotide with the reagent were determined at 30 and 50 degrees from the concentration dependence of the reaction yield and were 1988 +/- 83 and 1239 +/- 58 M-1, respectively. Experimental values of Kx agreed with the values of Kx = Kpx/(1 + Kh), calculated with the use of the thermodynamic parameters.