Table 1. Protonation Constants (log β) and pK Values of the Peptides at 298 K and a 0.1 M NaClO4 Ionic Strengtha.
| peptide | species | log β | log K | |
|---|---|---|---|---|
| DP1 | [HL]− | 9.62(3) | Lys | |
| [H2L] | 17.47(5) | 7.85 | Nterm | |
| [H3L]+ | 23.94(5) | 6.47 | His | |
| [H4L]2+ | 28.14(7) | 4.20 | Glu | |
| [H5L]3+ | 31.20(6) | 3.06 | Asp | |
| DP2 | [HL]− | 9.86(1) | Lys | |
| [H2L] | 16.87(2) | 7.01 | Nterm | |
| [H3L]+ | 22.78(2) | 5.91 | His | |
| [H4L]2+ | 27.48(2) | 4.70 | Glu | |
| [H5L]3+ | 31.37(2) | 3.89 | Asp | |
| Term-DEH | [HL]− | 10.82(1) | Lys | |
| [H2L] | 18.94(2) | 8.16 | Nterm | |
| [H3L]+ | 25.96(2) | 7.02 | His | |
| [H4L]2+ | 30.27(2) | 4.31 | Glu | |
| [H5L]3+ | 33.73(2) | 3.46 | Asp | |
| Mid-DEH | [HL]− | 10.52(1) | Lys | |
| [H2L] | 17.85(2) | 7.33 | Nterm | |
| [H3L]+ | 24.14(2) | 6.29 | His | |
| [H4L]2+ | 28.20(2) | 4.06 | Glu | |
| [H5L]3+ | 31.75(2) | 3.55 | Asp | |
| Bis-DEH | [HL]3– | 8.41(1) | 8.41 | Nterm |
| [H2L]2– | 15.82(1) | 7.41 | His | |
| [H3L]− | 22.49(1) | 6.67 | His | |
| [H4L] | 27.18(2) | 4.69 | Glu | |
| [H5L]+ | 31.23(2) | 4.05 | Glu | |
| [H6L]2+ | 34.59(2) | 3.36 | Asp | |
| [H7L]3+ | 37.26(2) | 2.67 | Asp |
a
Standard deviations (3σ values) are given in parentheses.