Table 2. Comparison of the ‘protein as supplied’ control with the average for each of the 28 formulations in BS9.
T m is the average of the difference (in C/K) between the T m of a sample in the formulation and the T m of the sample in the ‘protein as supplied’ positive control. The standard deviation of the difference is given in parentheses. The confidence interval shows the range in which the mean value would be statistically expected to lie at a 90% confidence level. The ‘No. of valid curves’ is the percentage of the 252 samples that were used to calculate the mean T m. ‘Valid curve increase’ shows how often the formulation yielded a valid curve when the ‘protein as supplied’ curve did not and ‘Valid curve decrease’ shows how often the formulation did not yield a valid curve when the ‘protein as supplied’ control did. The ‘Valid curve change’ is the difference of these two values. Rows in roman font describe formulations with 50mM salt; those in bold describe formulations containing 200mM salt. The three rows in italics are the formulations where the null hypothesis (i.e. that the formulation does not yield a T m > 0) is rejected at the 90% confidence level. All buffers are at 50mM in the formulations.
| Formulation | pH | T m | Confidence interval | 4 T m 30 (%) | No. of valid curves | Valid curve increase (%) | Valid curve decrease (%) | Valid curve change (%) |
|---|---|---|---|---|---|---|---|---|
| Salt only, 50mM NaCl | 1.2 (8.0) | (2.2, 0.1) | 15 | 168 | 2 | 19 | 17 | |
| Salt only, 200mM NaCl | 0.5 (8.2) | (0.5, +1.6) | 20 | 173 | 3 | 17 | 14 | |
| Sodium acetateacetic acid, 50mM NaCl | 5 | 5.3 (13.8) | (7.1, 3.4) | 14 | 153 | 4 | 25 | 21 |
| Sodium acetateacetic acid, 200mM NaCl | 5 | 7.6 (15.6) | (9.7, 5.6) | 12 | 158 | 4 | 23 | 19 |
| Piperazine, 50mM NaCl | 5.5 | 4.2 (9.8) | (5.4, 3.0) | 13 | 172 | 5 | 17 | 12 |
| Piperazine, 200mM NaCl | 5.5 | 1.2 (13.1) | (2.8, +0.5) | 16 | 173 | 5 | 17 | 12 |
| Sodium MES, 50mM NaCl | 6 | 1.3 (11.2) | (2.6, +0.1) | 19 | 182 | 4 | 1 | 9 |
| Sodium MES, 200mM NaCl | 6 | 1.1 (9.3) | (2.2, +0.0) | 19 | 185 | 4 | 12 | 8 |
| Trisodium citratecitric acid, 50mM NaCl | 6 | 0.0 (9.1) | (1.2, +1.1) | 21 | 174 | 4 | 17 | 13 |
| Trisodium citratecitric acid, 200mM NaCl | 6 | 1.3 (11.7) | (0.2, +2.8) | 23 | 171 | 7 | 18 | 11 |
| Bis-tris chloride, 50mM NaCl | 6.5 | 0.15 (8.2) | (1.2, +0.9) | 16 | 177 | 4 | 15 | 11 |
| Bis-tris chloride, 200mM NaCl | 6.5 | 0.8 (7.8) | (0.1, +1.8) | 19 | 176 | 4 | 16 | 12 |
| ADA, 50mM NaCl | 6.5 | 0.4 (8.2) | (1.5, +0.6) | 13 | 179 | 5 | 15 | 10 |
| ADA, 200mM NaCl | 6.5 | 1.5 (10.1) | (+0.2, +2.8) | 18 | 169 | 6 | 19 | 13 |
| Imidazole, 50mM NaCl | 7 | 0.6 (8.7) | (1.7, +0.5) | 16 | 178 | 4 | 15 | 11 |
| Imidazole, 200mM NaCl | 7 | 0.1 (7.7) | (1.1, +0.8) | 17 | 180 | 3 | 14 | 11 |
| Sodium MOPS, 50mM NaCl | 7 | 1.2 (8.2) | (2.2, 0.1) | 13 | 167 | 4 | 19 | 15 |
| Sodium MOPS, 200mM NaCl | 7 | 0.7 (9.4) | (0.5, +1.9) | 18 | 179 | 4 | 15 | 11 |
| Sodium HEPES, 50mM NaCl | 7.5 | 1.8 (8.2) | (2.8, 0.7) | 10 | 177 | 5 | 15 | 10 |
| Sodium HEPES, 200mM NaCl | 7.5 | 0.6 (7.5) | (1.5, +0.3) | 10 | 188 | 6 | 11 | 5 |
| Na2H/KH2 phosphate, 50mM NaCl | 7.5 | 1.0 (7.3) | (1.7, 0.1) | 10 | 180 | 4 | 14 | 10 |
| Na2H/KH2 phosphate, 200mM NaCl | 7.5 | 0.1 (9.9) | (1.1, +1.3) | 12 | 189 | 8 | 11 | 3 |
| Tris chloride, 50mM NaCl | 8 | 2.4 (7.9) | (3.4, 1.4) | 6 | 191 | 5 | 10 | 5 |
| Tris chloride, 200mM NaCl | 8 | 2.0 (8.0) | (3.0, 1.0) | 9 | 187 | 4 | 12 | 8 |
| Glycyl-glycine, 50mM NaCl | 8.5 | 3.2 (8.5) | (4.2, 2.2) | 10 | 187 | 6 | 12 | 6 |
| Glycyl-glycine, 200mM NaCl | 8.5 | 1.7 (8.8) | (2.8, 0.7) | 11 | 179 | 8 | 15 | 7 |
| CHES, 50mM NaCl | 9 | 4.8 (8.9) | (5.9 ,3.7) | 7 | 178 | 7 | 15 | 8 |
| CHES, 200mM NaCl | 9 | 4.6 (10.2) | (5.8, 3.3) | 8 | 184 | 10 | 13 | 5 |