Table 2. Spectroscopic Parameters of the Cu(II)/His-Leu Speciesa.
| UV–vis |
CD |
EPR |
||||||
|---|---|---|---|---|---|---|---|---|
| species | λ (nm) | ε (M–1 cm–1) | λ (nm) | Δε (M–1 cm–1) | giso | ACu (mT) | AN (mT) | binding mode |
| CuHL | n.d.b | n.d.b | 2.17 | 3.8 | 1.7 | Nim | ||
| 2.16 | 5.9 | 1.6 | Nim + Nam | |||||
| 0.9 | ||||||||
| CuL | 673 | 36 | 328 | –0.14 | 2.15 | 5.8 | 1.3 | Nim + Nam |
| 1.1 | ||||||||
| CuH–1L | 605 | 90 | 641 | –0.36 | 2.13 | 3.5 | 1.6 | Nam + N– + COO– |
| 496 | –0.05 | 1.2 | ||||||
| 328 | +0.35 | |||||||
| CuH–2L | 622 | 87 | 675 | –0.39 | 2.11 | 3.8 | 1.6 | Nam + N– + COO– + OH– |
| 567 | +0.03 | |||||||
| 499 | –0.15 | 1.1 | ||||||
| 319 | +0.36 | |||||||
| CuHL2 or CuL2 | 644 | 105 | 698 | +0.64 | 2.1 | 7.7 | 1.8 | 2Nam + Nim + CO |
| 332 | –0.32 | 1.1 | ||||||
| 1.1 | ||||||||
a
The UV–vis and CD parameters were calculated from experimental spectra using concentrations of individual species obtained from species distribution simulations based on stability constants listed in Table 1. The EPR parameters were obtained by spectral simulations using the EasySpin toolbox for Matlab R2017a.
b
Not determined.