Table 2. Summary of Data Used to Assign the Cluster Ligated Histidine with the Higher pKa Value to His134 and That with the Lower pKa Value to His154.
| nucleus observed | pKa | figure number | experiment |
|---|---|---|---|
| Oxidized TtRp at 278 K | |||
| His134 C′ | 8.68 ± 0.08 | 4A | 13C-[13C]-CT-COSY |
| His134 Cα | 9.22 ± 0.09 | 4B | 13C-[13C]-CT-COSY |
| His154 C′ | 7.89 ± 0.07 | 4A | 13C-[13C]-CT-COSY |
| His154 Cα | 7.56 ± 0.18 | 4B | 13C-[13C]-CT-COSY |
| His134 Nε2 | 9.16 ± 0.02 | 5B | 1D-15N rapid pulsing |
| His154 Nε2 | 7.58 ± 0.01 | 5B | 1D-15N rapid pulsing |
| Oxidized TtRp at 298 K | |||
| His134 Nε2 | 9.07 ± 0.02 | S3 | 1D-15N rapid pulsing |
| His154 Nε2 | 7.41 ± 0.01 | S3 | 1D-15N rapid pulsing |
| Reduced TtRp at 298 K | |||
| His134 C′ | 12.27 ± 0.03 | 4C | 13C-[13C]-CT-COSY |
| His134 Cα | 12.39 ± 0.05 | 4D | 13C-[13C]-CT-COSY |
| His154 C′ | 12.59 ± 0.03 | 4C | 13C-[13C]-CT-COSY |
| His154 Cα | 12.75 ± 0.09 | 4D | 13C-[13C]-CT-COSY |