Conformational peculiarities of alternating polynucleotides poly [d (G-C) .poly d (G-C) ] and poly [d (A-T) .poly [d (A-T) ] by 1H to 3H exchange
Maslova, R.N.; Lesnik, E.A.; Agranovich, I.M.; Minchenkova, L.E.; Varshavskiĭ, I.M.
Molekuliarnaia Biologiia 17(4): 726-733
1983
ISSN/ISBN: 0026-8984 PMID: 6621521 Document Number: 220067
The conformational changes of the alternating polynucleotides poly spectrum for I with an increase of the temperature up to 37.degree. as well as changing the water-NaCl (3 M) solution to a water-CF3CH2OH (64%) solution point to the existence of not only a single Z-form but a whole family of Z-forms for I differing in accessibility of C(8)H-groups to solvent. Retardation of the 1H .fwdarw. 3H exchange observed in II at 37.degree. C in 0.15 M NaCl compared to the exchange in poly(dA).cntdot.poly(dT) correlates with a model of B-alternating form for this polynucleotide. For the case of 6 M CsF the relative rate of exchange for C(8)H-groups of II and consequently the accessibility of these groups to solvent increases sharply, approaching the relative rate values for the Z-form of I in 3 M NaCl at the same temperatures. The CD spectrum of II in these conditions is also sharply increased. The conformation of II in 6 M CsF (not determined before) is considerably different from the B-alternating form of this polymer at a low ionic strength.