Figure 7

His to CO replacement reaction of GLB-26. The variation of absorption that occurs on the timescale of seconds was recorded in the visible region with a diode-array spectrophotometer. For the series of spectra, a decrease in absorbance at 560 nm is observed for increasing times. The observed spectral change is the same as the difference between the static spectra for the His and CO bound forms; this unambiguously assigns the slow transition after CO photo-dissociation (Figure 6) to the replacement of the internal His residue by CO. The insert shows the progression of the reaction, presented as the normalized fraction of the His bound form (the remainder in the CO bound form).