CC/GG contacts facilitate the B to A transition of DNA in solution.
Self-complementary decadeoxynucleotides, CCGATATCGG, CCAGATCTGG, CCCTGCAGGG, GGGGGCCCCC, were designed and synthesized to estimate the A-philic free energy of CC/GG contacts. First, regions of temperature-stability of the double-stranded conformation were determined for each 10-mer. Then, circular dichroism spectra were recorded for the B-family forms at different temperatures, counter-ion concentrations and trifluoroethanol contents. A cooperative change typical of the B-A transition is observed in the CD spectra at a trifluoroethanol content specific for each duplex. The positions of half-transition points were functions not only of the nucleotide sequence but of the duplex length as well: the B to A transitions were hindered in these 10-mers in comparison with a lengthy DNA. The B-phility value was estimated to be 3 kcal/mol of 10-mer. The B-A transition point was shown to drop with an increase in the number of CC/GG contacts in a duplex. The designed 10-mers made it possible to estimate quantitatively the A-phility of CC/GG contact as compared with an average DNA: (FA-FB)CC = 0.2 Kcal/mol, (FA-FB)DNA = 0.7 Kcal/mol.
Minchenkova
L E
LE
Institute of Molecular Biology, USSR Academy of Sciences, Moscow.
Schyolkina
A K
AK
Chernov
B K
BK
Ivanov
V I
VI
D001482:Base Composition; D001483:Base Sequence; D003016:Clostridium perfringens / Q000235:genetics; D004247:DNA; D004926:Escherichia coli / Q000235:genetics; D006358:Hot Temperature; D009161:Mycobacterium / Q000235:genetics; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D012996:Solutions; D013816:Thermodynamics
D012996:Solutions; D004247:DNA