Absorbance changes following flash photolysis of the CO complex with cytochrome <i>bd</i> in MV state.

<p>(a) Transient spectra in the Soret and visible regions at a delay time of ∼1.5 µs (<i>versus</i> pre-trigger). Dark cyan dashed lines: model spectra of electron transfer from heme <i>d</i> to heme <i>b</i>₅₉₅ constructed from individual reduced-<i>minus</i>-oxidized difference absorption spectra of the hemes published in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095617#pone.0095617-Bloch1" target="_blank">[56]</a>. Red solid line in <i>right panel</i>: expected spectrum. The expected spectrum is the transient spectrum for the R enzyme at a delay time of ∼1.5 µs (taken from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095617#pone-0095617-g005" target="_blank">Fig. 5a</a>, right panel) reduced by a factor of 2.5 to account for geminate recombination of CO to heme <i>d</i> that occurs in the MV enzyme at early times <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095617#pone.0095617-Vos1" target="_blank">[41]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095617#pone.0095617-Borisov17" target="_blank">[43]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095617#pone.0095617-Rappaport1" target="_blank">[46]</a>. (b), (c) and (d) Difference spectra of kinetic phases with τ ∼ 16 µs, 180 µs and 30 ms respectively. Buffer: 50 mM Hepes, 50 mM Ches, 0.1 mM EDTA, 0.05% sodium <i>N</i>-lauryl-sarcosinate, pH 8.0. Enzyme, 1.9 µM; CO, 1 mM. Optical pathway, 10 mm; excitation, 532 nm; temperature, 20 °C.