Table I.

Thermodynamic parameters of acid denaturation and chemical denaturation of SNase and SNase variants.

Reference	Variant	[KCl] mM	Osmolyte/Salt	pHmid	an	ΔG°H2O kcal/mol pH 7
WT		10		3.82 ± 0.02	3.60 ± 0.27
Δ+PHS		10		2.35 ± 0.02	3.77 ± 0.06
WT		100		3.79 ± 0.01	3.40 ± 0.12	5.4
PHS		100		2.91 ± 0.07	4.22 ± 0.18	8.5
Δ+PHS		100		2.06 ± 0.01	2.80 ± 0.12	11.8 ± 0.1
Δ+VIAGLA		100		2.02 ± 0.02	2.72 ± 0.12	12.5± 0.2
WT SNase		1000		3.68 ± 0.28	2.59 ± 0.13
Δ+PHS		1000		n/d
Δ+PHS		100	50mM SO4	n/d
Δ+PHS		100	300mM SO4	n/d
Δ+PHS		100		100mM NaClO4	2.02 ± 0.03	1.99 ± 0.04
Δ+PHS		100	1.5M Sucrose	n/d
Δ+PHS		100	300mM TMAO	1.90 ± 0.03	1.98 ± 0.07	13.1 ± 0.3
Δ+PHS		100	1M Glycerol	1.92 ± 0.03	2.41 ± 0.10	11.8 ± 0.3
Δ+PHS	D19N	100		1.95 ± 0.04	2.33 ± 0.25
Δ+PHS	D21N	100		2.19 ± 0.02	2.88 ± 0.11
Δ+PHS	R35Q	100		2.26 ± 0.02	2.37 ± 0.11
Δ+PHS	E57Q	100		3.46 ± 0.72	1.82 ± 0.98
Δ+PHS	R87Q	100		2.96 ± 0.05	2.86 ± 0.29
Δ+PHS	R35Q	R87Q	100		3.05 ± 0.17	3.49 ± 0.21
Δ+PHS	E135Q	100		2.03 ± 0.02	2.72 ± 0.12
Δ+VIAGLA		100		2.02 ± 0.02	2.72 ± 0.12	12.5 ± 0.2
Δ+VIAGLA	E10Q	100		2.03 ± 0.01	2.55 ± 0.10	11.7 ± 0.2
Δ+VIAGLA	D19N	100		1.8 ± 0.03	2.20 ± 0.11	13.2 ± 0.2
Δ+VIAGLA	D83N	100		2.32 ± 0.03	2.26 ± 0.06	10.8 ± 0.2
Δ+VIAGLA	D95N	100		2.2 ± 0.02	2.54 ± 0.14	10.8 ± 0.1
Δ+VIAGLA	H8Q	100		1.95 ± 0.01	2.60 ± 0.11	12.3 ± 0.2
Δ+VIAGLA	K16Q	100		2.03 ± 0.02	2.86 ± 0.23	11.9 ± 0.3
Δ+VIAGLA	K63Q	100		2.11 ± 0.02	2.67 ± 0.16	11.7 ± 0.2
Δ+VIAGLA	K71Q	100		1.98 ± 0.02	2.61 ± 0.13	12.2 ± 0.2
Δ+VIAGLA	K134Q	100		2.02 ± 0.01	2.78 ± 0.11	12.1 ± 0.2
Δ+VIAGLA	D77N
	D83N	100		2.73 ± 0.04	2.07 ± 0.06	8.8 ± 0.1
Δ+VIAGLA	E10Q
	D19N
	D77N
	D83N	100		2.83 ± 0.05	1.72 ± 0.09	8.7 ± 0.1
Δ+VIAGLA	E10Q
	D19N
	D77N
	D83N
	D95N	100		3.25 ± 0.20	1.35 ± 0.25	6.5 ± 0.1
WT		100	100mM NaClO4	3.79 ± 0.02	2.73 ± 0.12
WT		100	50mM SO4	3.6 ± 0.03	2.77 ± 0.13
WT	E10A	100		4.02 ± 0.01	2.89 ± 0.11	3.7 ± 0.3
WT	D19A	100		4.07 ± 0.01	3.27 ± 0.18	4.6 ± 0.1
WT	D77A	100		4.08 ± 0.02	2.31 ± 0.08	2.1 ± 0.2
WT	D83A	100		4.42 ± 0.11	2.35 ± 0.48	1.3 ± 0.5
WT	D95A	100		4.61± 0.35	3.25± 0.45	1.3 ± 0.3

^aSlope of the pH titration curves, which is proportional to the net number of H⁺ bound preferentially to the U state over the N state upon acid unfolding.