DNA helices function as good molecular scaffolds for analyzing spin-spin coupling due to their stable structures and well-understood conformations.  This research focuses on 4 specific DNA helices that have identical 19-base pair nucleotide sequences and a 3-carbon chain nitroxide radical attachment to one 5' phosphate.  The only difference within this family of nucleic acids is the location of an  EDTA-modified thymidine base on the complementary chain.  Upon addition of a lanthanide ion, the EDTA(Ln(III)) moiety binds to the strand possessing the nitroxide radical.  Exchange couplings observed between the EDTA(Dy(III)) and the nitroxide radical electron are remarkably strong. Distance ratios predicted by the observed spin-spin couplings have been used to estimate the nitroxide radical position to �5% error.  However, not all regions of space were thoroughly explored using this method, and a complete 3-dimensional analysis using a trilateration technique was developed to test all points.

Modeling orientations of a nitroxide spin label in 3D space

240th National Meeting (2010)

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