Dimethylsulfoxide-stabilized conformer of guanine-adenine repeat strand ofDNA

Circular dichroism spectroscopy and other methods are used to show that the addition of dimethylsulfoxide causes reversible folding of the (GA)(10) st rand of DNA into an ordered single-stranded conformer. The ordered conforme r melts in a cooperative way and it does not contain protonated adenine. Th e (TA)(10), (A)(20), and (G)(20) are all unstable in this conformer. To the best of our knowledge, this is the first known ordered conformer of DNA th at is stabilized by dimethylsulfoxide. This conformer might be a DNA analog of the protein alpha helix, which is an interesting idea for thinking abou t the evolution of DNA. (C) 2001 John Wiley & Sons, Inc.