Table IV.

Thermal and Chemical Denaturation Midpoints

MexR Variants and Complexes			Tm (°C)
wt	<20a	55.6
wt PI			56.6
wt PII	26.8	57.1
L13M			47.8
R21W	33.6	70.9		0.6	2.6
G58E	32.6	62.6
R70W	25.2	56.4		<1a

and refers to the thermal melting points of the first and second transition in a three-state denaturation, whereas T_m refers to the melting temperature in a two-state transition. and refer to the corresponding chemical midpoint of denaturation.³⁵ The corresponding fits are shown in Figure 4(C,D).

^aThe T_m of the first transitions in MexR-wt, MexR-wt-PII DNA, and MexR-R70W are less accurate because the entire transition was not complete within the temperature range of the experiment; these T_m's are, therefore, to be interpreted only qualitatively. Each experiment was performed thrice with average standard deviations of 0.5°C for , 0.3°C for , and 0.8°C for T_m. The chemical denaturation experiment was performed once, with estimated errors of ±0.2M in and ±0.1M in .