Table I. Number of unambiguously identified disulfide-bridged peptides from a mixture of six standard proteins.
| Protein name | Number of free cysteinesa | Number of disulfide bridgesa | Trypsin (pH 7.8) | Trypsin (pH 6.8) | Pepsin (pH 1.5) |
|---|---|---|---|---|---|
| Cytochrome C | 2 | 0 | 0 | 0 | 0 |
| IgG | 0 | 16 | 8 | 6 | 12 |
| Bovine serum albumin | 1 | 17 | 11 | 7 | 13 |
| Lysozyme C | 1 | 4 | 1 | 1 | 4 |
| Ribonuclease B | 0 | 4 | 1 | 0 | 2 |
| β-lactoglobulin | 3 | 2 | 1 | 2 | 0 |
| Total | 7 | 43 | 22 | 16 | 31 |
| Observed artificial intraprotein disulfide bonds | - | - | 8 | 1 | 0 |
| Observed artificial interprotein disulfide bonds | - | - | 6 | 0 | 0 |
a As extracted from crystal structures.