DNA DYNAMICS FROM A SPIN PROBE - DEPENDENCE OF PROBE MOTION ON TETHER LENGTH

The phosphoramidite 6, a spin labeled analog of thymidine, was synthesized and incorporated into the deoxyoligonucleotide 5′-d(CGCGAATT*CGCG). This substance adepts a duplex structure, as shown by gel electrophoretic mobility. The EPR spectrum of the spin labeled duplex in solution was indicative of subnanosecond probe motion, a result which contrasts with the ca. 5 ns correlation time determined for the corresponding duplex bearing residue 1. Steric inhibition of rotation of the nitroxide-bearing ring of 1 not present in 2 accounts for this difference. © 1990.