TABLE 2.
Deuterium effect on time constants of photocycle and kinetics of proton uptake and release in wild type ESR
| τ1a | τ2 | τ3 | τ4 | τ5 | τ6 | τuptakeb | τrelease | |
|---|---|---|---|---|---|---|---|---|
| μs | μs | μs | ms | ms | ms | ms | ms | |
| H2O, pH 7.2 | 5.5 ± 0.5 | 25 ± 5 | 146 ± 7 | 1.00 ± 0.03 | 15.0 ± 0.6 | 64 ± 2 | 0.90 ± 0.05 | 66 ± 3 |
| D2O,c pD 7.6 | 9.6 ± 0.1 | 62 ± 4 | 410 ± 14 | 3.00 ± 0.07 | 32.0 ± 1.1 | 90 ± 2 | 2.0 ± 0.1 | 96 ± 4 |
| Ratio D2O/H2O | 1.8 ± 0.3 | 2.5 ± 0.3 | 2.8 ± 0.3 | 3.00 ± 0.15 | 2.1 ± 0.2 | 1.4 ± 0.1 | 2.2 ± 0.2 | 1.4 ± 0.13 |
a Time constants τ1–τ6 were obtained from global fit of light-induced absorption changes at 410, 510, 550, and 590 nm in 0.05% lyso-PG, 0.1 m NaCl, 23 °C.
b Since there is some variation in time constants in different preparations of ESR, the time constants in this table were all obtained from a single preparation.
c Data were after 3 days of incubation in D2O.