Table 3.

Thermodynamic parameters for thermal denaturation of Ejl amidase in 20 mM phosphate buffer, pH 8.0a

[Choline] (mM)	Tm1b (°C)	ΔH1c (kcal mol−1)	ΔH1vHc (kcal mol−1)	Tm2b (°C)	ΔH2c (kcal mol−1)	ΔH2vHc (kcal mol−1)	Tm3b (°C)	ΔH3 (kcal mol−1)	ΔH3vHc (kcal mol−1)	ΔHd (kcal mol−1)
0	42.9	84	72	—	—	—	48.0	109	130	192
3	42.8	59	66	—	—	—	49.5	133	152	188
5	43.2	63	65	—	—	—	50.3	144	159	206
10	39.6	36	78	49.4	44	93	52.3	140	231	223
20	40.4	53	73	50.2	47	88	55.2	130	258	228
40	40.2	46	63	51.5	54	103	58.1	141	317	239
80	39.7	37	73	52.3	55	80	62.1	158	373	255
140	41.7	34	72	51.7	54	100	65.0	155	404	238
280	39.4	29	84	49.5	58	72	68.2	193	386	280

^a Ejl concentration was 27.4 μM. ΔH_i is the calorimetric enthalpy change of transition i; ΔH_ivH is the van't Hoff enthalpy of transition i, calculated as 4RT_miΔCp_mi / ΔH_i, where ΔCp_mi is the maximum of the Cp function, T_mi is the temperature of the maximum, and R is the gas constant. ΔH_d is the total denaturation enthalpy change. Calorimetric ΔH values are in kcal per mole of Ejl monomer.

^b Estimated error ±0.3°C.

^c Estimated error ±12%.