NMR and CD studies on an oligonucleotide containing N4-methylcytosine.
The hexamer d(CGm4CGCG) exists predominantly as a right handed B form helix at 20 degrees C in 150 mM NaCl, as shown by 2D NOE spectra. Under these conditions a minor species is also observed which corresponds to the single strand in slow exchange on a proton NMR time scale with the double strand. This exchange is unusually slow and separate resonances for the two species are seen up to 65 degrees C. At 50 degrees C the lifetime of the single strand species is 0.85 s. Under high salt conditions the hexamer is partly converted into the Z form, but the complete transition is only observed at 5M NaCl at -6 degrees C.
D002942:Circular Dichroism; D003596:Cytosine / Q000031:analogs & derivatives*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009690:Nucleic Acid Conformation; D009843:Oligoribonucleotides
D009843:Oligoribonucleotides; C039052:N(4)-methylcytosine; D003596:Cytosine