Table 2. Protonation Constants (log β) and pK Values of the Cu(II)–Peptide Systems at 298 K and a 0.1 M NaClO4 Ionic Strengtha.
| peptide | species | log β | log K | |
|---|---|---|---|---|
| DP1 | [CuH2L]2+ | 22.83(6) | ||
| [CuHL]+ | 18.66(4) | 4.17 | Glu | |
| [CuL] | 14.19(2) | 4.47 | N–amide | |
| [CuLH–1]− | 9.11(2) | 5.08 | N–amide | |
| [CuLH–2]2– | 0.11(4) | 9.00 | Lys | |
| [CuLH–3]3– | –10.05(4) | 10.16 | Owater | |
| DP2 | [CuHL]+ | 20.81(2) | ||
| [CuL] | 15.90(4) | 4.91 | Glu | |
| [CuLH–1]− | 8.17(4) | 7.73 | N−amide | |
| [CuLH–2]2– | –1.26(4) | 9.43 | N−amide | |
| [CuLH–3]3– | –11.13(5) | 9.87 | Lys | |
| Term-DEH | [CuH2L]2+ | 24.17(3) | ||
| [CuHL]+ | 18.83(2) | 5.34 | Nterm | |
| [CuL] | 12.46(2) | 6.37 | N−amide | |
| [CuLH–1]− | 3.62(4) | 8.84 | N−amide | |
| [CuLH–2]2– | –5.22(3) | 8.84 | N−amide | |
| [CuLH–3]3– | –16.27(4) | 11.05 | Lys | |
| Mid-DEH | [CuH2L]2+ | 22.16(3) | ||
| [CuHL]+ | 17.57(1) | 4.59 | Nterm | |
| [CuL] | 11.86(1) | 5.71 | N−amide | |
| [CuLH–1]− | 3.09(2) | 8.77 | N−amide | |
| [CuLH–2]2– | –6.38(2) | 9.47 | N−amide | |
| [CuLH–3]3– | –17.58(2) | 11.20 | Lys | |
| 1:1 Bis-DEH | [CuH2L]2+ | 22.53(1) | ||
| [CuL] | 12.87(1) | 9.66 | Nterm, 2 × N−amide | |
| [CuLH–1]− | 7.28(2) | 5.59 | ||
| [CuLH–2]2– | –0.45(4) | 7.73 | His | |
| 2:1 Bis-DEH | [CuH2L] | 22.53(1) | ||
| [CuL]2– | 12.87(1) | 9.66 | Nterm, 2 × N−amide | |
| [CuLH–1]3– | 7.28(2) | 5.59 | ||
| [Cu2LH–2]2– | 4.34(9) | |||
| [Cu2LH–3]3– | –2.83(5) | 7.17 | N−amide | |
| [Cu2LH–4]4– | –11.14(7) | 8.31 | N−amide | |
| [Cu2LH–5]5– | –22.35(7) | 11.21 | Owater |
a
Standard deviations (3σ values) are given in parentheses.