TABLE 2. Thermodynamic parameters for NPG binding.

Experiments were carried out in NaP_i, pH 7.5, as described under “Experimental Procedures.”

LacY	T	Ka	Kda	ΔH	ΔGb	TΔSc	ΔS	ΔCpd
	K	M−1	µM	kcal·mol−1	kcal·mol−1	kcal·mol−1	cal·mol−1·K−1	cal·mol−1·K−1
Wild type	279	8.4 × 104	12	−0.3	−6.3	6.0	21.6	−156.5
	280	7.5 × 104	13	−0.3	−6.3	6.0	21.2
	288	1.0 × 105	10	−1.2	−6.6	5.4	18.9
	293	7.8 × 104	13	−2.2	−6.6	4.4	15.0
	298	7.6 × 104	13	−3.3	−6.7	3.4	11.5
C154G	279	4.6 × 105	2	−11.6	−7.2	−4.4	−15.8	−124.5
	288	3.0 × 105	3	−13.4	−7.2	−6.2	−21.4
	293	2.1 × 105	5	−13.5	−7.1	−6.4	−21.8
	298	1.7 × 105	6	−14.1	−7.1	−7.0	−23.5

^aK_d = 1/K_a.

^bΔG was calculated by the equation ΔG = −RT lnK_a.

^cTΔS was calculated by the equation TΔS = ΔH − ΔG.

^dΔC_p = ΔH/dT was determined from the slope of the linear fit in Fig. 4.