TABLE 7. Comparison Between Computed and Observed pKa's in BPTIa.
| residue | (pKa0)b | (pKaexp)c | (pKacal)d | (pKacal)e | (pKa)f | (pKa)g | (pKa)h | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| DI = 2 | DI = 4 | DI = 8 | DI = 16 | DI = 2 | DI = 4 | DI = 8 | DI = 16 | ||||||
| NEND1 | 7.5 | 8.1 | 5.3 | 6.5 | 7.1 | 7.6 | 5.8 | 6.6 | 7.2 | 7.3 | 7.2 | 7.5 | – |
| ARG1 | 12.0 | – | 12.8 | 16.1 | 15.8 | 15.4 | 12.8 | 15.6 | 14.8 | 14.5 | 18.1 | 13.6 | – |
| ASP3i | 4.0 | 3.0 | 1.8 | 1.8 | 1.9 | 2.0 | 2.4 | 2.5 | 3.3 | 3.2 | 3.4 | 3.3 | – |
| GLU7 | 4.4 | 3.7 | 14.9 | 6.1 | 4.1 | 2.9 | 14.4 | 6.4 | 5.3 | 4.1 | 5.4 | 3.7 | – |
| TYR10 | 9.6 | – | 12.7 | 9.5 | 8.8 | 8.5 | 12.5 | 9.6 | 9.4 | 9.2 | 9.9 | 9.6 | – |
| LYS15 | 10.4 | 10.6 | 9.4 | 10.4 | 10.8 | 10.8 | 9.9 | 10.4 | 10.7 | 10.6 | 10.4 | 10.5 | – |
| ARG17 | 12.0 | – | 12.2 | 12.6 | 12.6 | 12.6 | 12.0 | 12.4 | 12.3 | 12.0 | 12.2 | 12.2 | – |
| ARG20 | 12.0 | – | 9.4 | 12.8 | 13.4 | 13.5 | 9.5 | 12.6 | 12.6 | 12.7 | 13.1 | 12.9 | – |
| TYR21 | 9.6 | – | 12.6 | 10.5 | 9.7 | 9.4 | 12.5 | 10.7 | 9.9 | 9.7 | 10.1 | 9.5 | – |
| TYR23 | 9.6 | – | 21.5 | 13.0 | 10.2 | 9.5 | 21.2 | 13.0 | 10.2 | 9.7 | 11.3 | 10.6 | – |
| LYS26 | 10.4 | 10.6 | 10.5 | 10.7 | 11.1 | 10.9 | 10.6 | 10.8 | 10.8 | 10.7 | 10.4 | 10.6 | – |
| TYR35 | 9.6 | – | 17.1 | 10.9 | 8.8 | 8.1 | 16.8 | 11.1 | 9.5 | 8.9 | 9.5 | 8.5 | – |
| ARG39 | 12.0 | – | 11.9 | 12.8 | 12.9 | 12.8 | 11.8 | 12.5 | 12.2 | 12.2 | 12.2 | 12.4 | – |
| LYS41 | 10.4 | 10.8 | 8.8 | 11.3 | 11.5 | 11.4 | 9.0 | 11.3 | 11.2 | 11.1 | 10.2 | 10.8 | – |
| ARG42 | 12.0 | – | 11.8 | 12.9 | 12.9 | 12.9 | 11.7 | 12.6 | 12.1 | 12.1 | 13.0 | 12.5 | – |
| LYS46 | 10.4 | 10.6 | 8.9 | 9.8 | 10.2 | 10.6 | 9.3 | 9.9 | 10.3 | 10.4 | 10.0 | 10.3 | – |
| GLU49 | 4.4 | 3.8 | 4.4 | 3.6 | 3.5 | 3.2 | 4.9 | 4.3 | 4.3 | 4.1 | 3.8 | 3.7 | – |
| ASP50 | 4.0 | 3.4 | 1.8 | 1.5 | 1.8 | 2.4 | 2.5 | 2.5 | 2.7 | 2.6 | 2.3 | 2.6 | – |
| ARG53 | 12.0 | – | 15.1 | 14.7 | 14.2 | 13.9 | 14.8 | 14.3 | 13.3 | 13.1 | 12.9 | 13.0 | – |
| CEND58 | 3.8 | 2.9 | 1.5 | 1.7 | 1.8 | 2.1 | 2.3 | 2.4 | 3.0 | 2.9 | 3.9 | 3.3 | – |
| (Δav)j | 2.5 | 1.0 | 0.8 | 0.6 | 2.0 | 0.8 | 0.5 | 0.3 | 0.7 | 0.3 | 0.6 | ||
| (Δmax)k | 3.2 | 2.4 | 1.6 | 1.0 | 3.1 | 2.7 | 1.4 | 0.8 | 1.7 | 0.8 | 1.5 | ||
a
In pK units, computed by eq 18.
b
Value of pKa0 of the residues at T = 300 K.51
c
Experimental values of pKaexp for the residue in 0.2 M NaCl and at T = 300 K.51
d
Calculated pKa for BPTI using D0 = 80 and DI = 2, 4, 8, and 16 in 0.0 M salt at T = 300 K.
e
Calculated pKa for BPTI using D0 = 80 and DI = 2, 4, 8, and 16 in 0.15 M of 1.1 salt at T = 300 K.
f
Calculated in ref 50 at 0.15 M ionic strength and T = 293 K.
g
Calculated in ref 51.
h
Calculated in ref 52. Dashes indicate that the pKa's for these ionizable groups were not reported in ref 52.
j
Average value of the absolute difference between observed and computed pKa's.
k
Maximum deviation between observed and computed pKa's.