Table 1.
Unfolding Temperatures (T m) of Human IgG Over a Range of pH Conditions, as Determined From DSF Analysis, Along With Corresponding Buffers Used and Their pKa.a
| pH | Buffer | pKa at 25°C | IgG T m (°C) |
|---|---|---|---|
| 3.0 | PBS | 2.2 | 39 ± 1b |
| 4.0 | Sodium Acetate | 4.8 | 50.1 ± 0.4* |
| 5.0 | Sodium Acetate | 4.8 | 66.1 ± 0.3c |
| 6.0 | PIPES | 6.8 | 69.3 ± 0.2d, f |
| 7.0 | PIPES | 6.8 | 70.5 ± 0.2e |
| 7.0 | PBS | 7.2 | 69.7 ± 0.3d, e |
| 8.0 | CHES | 9.5 | 68.8 ± 0.1f |
| 9.0 | CHES | 9.5 | 67.4 ± 0.3c |
| 10.0 | CAPS | 10.4 | 63.4 ± 0.1* |
| 12.0 | PBS | 12.4 | 37 ± 2b |
Abbreviations: ANOVA, analysis of variance; CHES, 2-(Cyclohexylamino)ethane sulfonic acid CAPS, 3-(Cyclohexylamino)-1-propanesulfonic acid; DSF, differential scanning fluorimetry; IgG, immunoglobulin G; PBS, phosphate-buffered saline; PIPES, 1,4-Piperazinediethanesulfonic acid; SEM, standard error of mean.
aData are presented as means ± SEM (n = 4). One-way ANOVA with post hoc Tukey test showed that T m results were all significantly different from each other (P < .05), except for results labeled with the same superscript letter, which was not significantly different. Results marked with an asterisk (*) are significantly different from all other unfolding temperatures (P < .05).