SYNTHESIS AND CHARACTERIZATION OF DISULFIDE CROSS-LINKED OLIGONUCLEOTIDES

Disulfide cross-linked derivatives of the ''Dickerson/Drew dodecamer'' 5'-d(CGCGAATTCGCG)-3' and the related decamer 5'-d(GCGAATTCGC)-3' have been synthesized, each bearing a dithiobis(ethane) (C2) or dithiobis-(propane) (C3) cross-link at the central adenine (A). NMR and CD spectroscopy indicate that these duplexes are essentially undistorted relative to native B-DNA. However, cross-linking does confer a large degree of stabilization upon the duplexes, as reflected in increased melting temperatures of 15-21-degrees-C for the cross-linked oligonucleotides relative to those for the native sequences. In contrast, un-cross-linked tethers at the same adenines cause substantial decreases in the melting temperature. The cross-linked duplexes were also found to be stable to millimolar concentrations of beta-mercaptoethanol, an important feature for future applications of these cross-links to the study of protein-DNA interactions.