(A) Time courses for rebinding of CO to BvHb1.2, after flash photolysis, monitored at 416 nm. The binding is a double exponential process at all CO concentrations (from left to right: 500, 250, 125, and 63 µM). (B) Fast phase and (C) Slow phase of the rebinding of CO to the three BvHbs. For BvHb1.1 and BvHb1.2 (both class-1) the approximate rates of the slow phase are essentially the same as reported by stopped-flow (Figure 2B). For BvHb2, this slow phase is faster than the value given by stopped-flow spectrometry. The closed and open symbols correspond to kobs values monitored at 429 nm for BvHb2 and 416 nm and 430 nm for BvHb1.1 and BvHb1.2.