Influence of dA X dT and d(2aminoA) X dT base pairs on the B in equilibrium Z transition of DNA fragments. 1H-NMR study of d(C-G-C-A-m5C-G-T-G-m5C-G), d(m5C-G-C-A-m5C-G-T-G-C-G) and d(C-2aminoA-C-G-T-G).
The Helical structures of d(C-G-C-A-m5C-G-T-G-m5C-G), d(m5C-G-C-A-m5C-G-T-G-C-G) and d(C-2aminoA-C-G-T-G) were studied in aqueous solution at various salt concentrations and temperatures by 1H-NMR spectroscopy. In 0.1 M NaCl solution only the B form was evidenced for these DNA fragments whereas in 4 M NaCl both B and Z forms, in slow exchange on the NMR time scale, were observed. Under these conditions the Z form accounted for less than 60% of the decamer conformation; conversely d(C-G)3 hexamers containing methylated cytidines were predominantly in the Z form (greater than 90%) [Tran-Dinh et al. (1984) Biochemistry 23, 1362; Cavaillès et al. (1984) J. Biomol. Struct. Dyn. 1, 1347-1371]. On the other hand, d(C-2aminoA-C-G-T-G) in which the d(2aminoA) X dT base pair forms three hydrogen bonds, was found to adopt the Z conformation in 4M NaCl solution which was not the case for d(C-A-C-G-T-G) (unpublished results). The present study shows that the B in equilibrium Z transition in solution is highly sequence-dependent and that correlation exists between the stability of the duplexes (essentially governed by the number of hydrogen bonds between complementary bases) and their ability to adopt the Z conformation.
Cavaillès
J A
JA
Neumann
J M
JM
Tran-Dinh
S
S
Huynh-Dinh
T
T
d'Estaintot
B L
BL
Igolen
J
J
D001482:Base Composition; D055598:Chemical Phenomena; D002621:Chemistry; D004247:DNA; D009682:Magnetic Resonance Spectroscopy; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis; D009841:Oligonucleotides / Q000138:chemical synthesis; D011522:Protons; D012965:Sodium Chloride; D012996:Solutions; D013816:Thermodynamics
D009838:Oligodeoxyribonucleotides; D009841:Oligonucleotides; D011522:Protons; D012996:Solutions; D012965:Sodium Chloride; D004247:DNA