. 1998 Aug 4;95(16):9244–9249. doi: 10.1073/pnas.95.16.9244

Table 2.

Specificity of RNAs with backbone modifications

RNA molecule	Contacts affected by modification	Modified phosphate oxygen	K_d, nM		Specificity
RNA molecule	Contacts affected by modification	Modified phosphate oxygen	U-RNA	C-RNA	Specificity
RNAs 5 and 6
Unmodified			10, 1.7^*	0.04^*	146
Deoxy −5	Glu-63		270, 23^*	1.8^*	81
RNAs 7 and 8
Unmodified			13, 4.1^*	0.04^*	214
R_P-thioP-3	None	O1P	19, 4.8^*	0.04^*	298
S_P-thioP-3	None	O2P	9.4, 5.7^*	0.03^*	252
R_P-thioP-7	Lys-57	O1P	2.7, 1.4^*	0.05^*	41
S_P-thioP-7	Asn-55, Ser-52	O2P	51, 15^*	1.3^*	25
S_P-methylP-7	Lys-57	O1P	88, 16^*	26^*	2.0
R_P-methylP-7	Asn-55, Ser-52	O2P	295, 34^*	18^*	9.1
R_P-thioP-6	Cytosine-5	O1P	0.6, 0.2^*	0.02^*	20
S_P-thioP-6	None	O2P	7.9, 2.1^*	0.03^*	167
DithioP-6	Cytosine-5	O1P, O2P	0.4, 0.06^*	0.04^*	5.8
S_P-methylP-6	Cytosine-5	O1P	17, 6.2^*	23^*	0.5
R_P-methylP-6	None	O2P	34, 9.2^*	3.3^*	6.5

K_d values were measured in 80 mM KCl/10 mM MgCl₂/100 mM K–Hepes, pH 7.5, at 0°C. Specificity is defined as K_d (U-RNA)/K_d (C-RNA) and was calculated by using an average of the kinetic and thermodynamic determinations of the U-RNA.

Calculated by dividing the experimental off-rate by 10⁸ M⁻¹⋅min⁻¹.