Table 1.

Standard State Free Energy of Dimer Formation between the 118-nt A/b′ pRNA and br_B/a′^a

label positionb		Kd (nM)c	ΔG°17 °C (kcal/mol)d	ΔΔG°17 °C (kcal/mol)e
None		175 ± 63	−8.96 ± 0.26	-
Single labeled	(26; --)	273 ± 99	−8.71 ± 0.26	0.25
	(33; --)	219 ± 94	−8.83 ± 0.32	0.13
	(37; --)	196 ± 32	−8.90 ± 0.10	0.06
	(66; --)	198 ± 27	−8.89 ± 0.08	0.07
	(76; --)	249 ± 109	−8.76 ± 0.33	0.20
	(79; --)	203 ± 101	−8.88 ± 0.40	0.08
	(88; --)	601 ± 326	−8.25 ± 0.45	0.71
	(95; --)	252 ± 119	−8.75 ± 0.37	0.21
Double labeled	(26; 37)	493 ± 121	−8.36 ± 0.16	0.60
	(26; 76)	616 ± 158	−8.24 ± 0.17	0.73
	(26; 79)	657 ± 160	−8.20 ± 0.16	0.76
	(26; 88)	929 ± 200	−8.00 ± 0.14	0.96
	(33; 76)	449 ± 73	−8.42 ± 0.10	0.52
	(33; 79)	522 ± 16	−8.33 ± 0.02	0.63
	(33; 95)	411 ± 143	−8.47 ± 0.25	0.49
	(37; 76)	497 ± 131	−8.36 ± 0.18	0.60
	(37; 79)	320 ± 5	−8.61 ± 0.01	0.35
	(37; 88)	617 ± 158	−8.24 ± 0.17	0.72
	(37; 95)	313 ± 121	−8.63 ± 0.28	0.33
	(66; 76)	235 ± 56	−8.79 ± 0.16	0.17
	(66; 79)	319 ± 59	−8.61 ± 0.12	0.35
	(66; 95)	297 ± 33	−8.66 ± 0.07	0.30
	(76; 95)	228 ± 1	−8.81 ± 0.00	0.15
	(79; 95)	284 ± 52	−8.68 ± 0.12	0.28
	(88; 95)	402 ± 79	−8.48 ± 0.13	0.48

^aMeasurements were carried out at 17 °C in 50 mM Tris-HCl, pH 7.6, 3 mM MgCl₂ as described in Materials and Methods.

^bDesignated by the sequence number(s) of the R5 attachment site(s).

^cErrors obtained from multiple measurements.

^dErrors calculated from propagating errors of K_d measurement.

^eΔΔG° = ΔG°(spin labeled br_B/a′) − ΔG°(unmodified br_B/a′).