The DEER-derived interprobe distance distributions for mini TAR DNA doubly labeled at diametrically opposite phosphorothioate positions CD or EF in the TAR upper stem. The DNA was annealed to complementary unlabeled mini TAR RNA in the presence of NCp7 to form hybrid DNA-RNA duplexes. In panel a, the black line is SLCD by itself, the green trace is from a 1:1 mixture of SLCD + mini TAR RNA, the magenta trace is a 1:1:1 mixture of SLCD mini TAR DNA/mini TAR RNA/NCp7, the red trace is from a 1:1:4 mixture of SLCD mini TAR DNA/mini TAR RNA/NCp7, and finally, the blue traces is a thermally annealed mixture of 1:1 mixture of doubly labeled SLCD and mini TAR RNA. Panel b shows the same combinations as panel a, but with SLEF substituted for SLCD. Sample conditions were 20 mM HEPES, 20 mM NaCl, 0.2 mM MgCl2, pH 7.5 with 10% glycerol. The samples were deuterated as described in Materials and Methods.