Table 4.

Thermodynamic parameters for the equilibrium transitions observed with wild-type and mutant β-lactamase

Sample	ΔGNI*, kcal/mol	mNI*, kcal/liter	FI†, % N	ΔGIU‡, kcal/mol	mIU‡, kcal/liter	ΔGNU§, kcal/mol
Wild type	4.1  ± 0.2	4.9  ± 0.3	82  ± 1	5.9  ± 0.5	2.6  ± 0.3	10.0  ± 0.7
M182T	6.3  ± 0.7	6.4  ± 0.7	67  ± 4	3.0  ± 0.6	1.5  ± 0.2	9.3  ± 1.3
L76N	6.2  ± 0.6	4.3  ± 0.4	90  ± 7	4  ± 1	1.9  ± 0.4	10.2  ± 1.6
L76N:M182T	3.4  ± 0.2	5.1  ± 0.3	56  ± 8	2.7  ± 1.6	1.2  ± 0.8	6.1  ± 1.8

^*ΔG_o for the transition from N to I as measured by fluorescence. As a single transition, this first denaturation process is more accurately determined by fluorescence. The second transition by CD spectroscopy was determined by forcing the first transition to correspond to that monitored by fluorescence. The m values are slopes of plots of ΔG against the Gdn·HCl concentration. Pre- and post-transition changes in the signal were treated as linear functions as described (31). 

^† The CD signal (at 220 nm) of the intermediate as a percentage of the CD signal of the native protein. 

^‡ ΔG_o and m for the transition from I to U. 

^§ ΔG_o for the transition between N and U.