Table V.

Parameters Characterizing the Urea Unfolding of RNase T1 and Hydrogen Bonding Variants in 30 mM MOPs, pH 7.0, 25°C

Variant	Urea1/2a (M)	ΔUrea1/2b (M)	mc (cal mol−1 M−1)	ΔG (H2O)d (kcal mol−1)	ΔΔGe (kcal mol−1)
WT	5.20	–	1172	6.1	–
T91A	2.32	−2.88	1250	2.9	−3.4
T91V	2.07	−3.13	1243	2.6	−3.7
T93A	4.46	−0.74	911	4.1	−0.9
T93V	4.16	−1.04	1201	5.0	−1.2
T91A, T93A	1.90	−3.30	1210	2.3	−3.9
T91A, T93V	2.35	−2.85	1215	2.9	−3.4
T91V, T93A	1.90	−3.30	1335	2.5	−3.9
T91V, T93V	2.19	−3.01	1324	2.9	−3.6

^aMidpoint of the unfolding curve. The error is ± 2%.

^bΔUrea_1/2 = Urea_1/2 (variant) − Urea_1/2 (WT).

^cThe slope of plots of ΔG versus [Urea]. The error is ± 10%.

^dΔG (H₂O) = the intercept of plots of ΔG versus [Urea] at 0M Urea.

^eFrom ΔUrea_1/2 × the average m value of WT and the variants (1192 cal mol⁻¹ M⁻¹). The negative values indicate a decrease in stability.