SOME INTERESTING PROPERTIES OF DUPLEX AND TETRAPLEX DNA

Ben Luisi^*, Zippi Shakked, David Lilley et al.

^*Department of Biochemistry
Tennis Court Road, Cambridge University Cambridge, CB2 1QW England

Some intriguing features of duplex and tetraplex DNA structures will be described. In duplex DNA, certain base-steps tend to have a high degree of propeller twist. Steps of the type ApA=TpT may have such a high degree of propeller twist that a cross-strand hydrogen bond results. Surprisingly, steps of the type ApI=MpT (I=inosine and M= 5-methyl-Cytosine) are also propeller twisted, to such an extent that they bring two amino groups into close contact. Is this an attractive interaction ? Evaluation of the small molecule structural database and calculations will be presented that suggest that this may be an attractive contact.

The crystal structure of a parallel-stranded DNA tetraplex has been refined to very high resolution, and some of the distinctive features will be described.