Time-resolved infrared studies of molecular diffusion in myoglobin

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Abstract
Transient infrared absorbance changes of photolyzed carbon monoxide are used to probe internal dynamics in myoglobin over the time range 50 ns to 10 μs and the temperature range 100 to 240 K. The infrared absorbance of the photolyzed carbon monoxide at temperatures above 170 K disappears long before the CO recombines with the iron, indicating that the carbon monoxide experiences substantial time-dependent heterogenous line broadening. We argue that this broadening occurs as the carbon monoxide diffuses a substantial distance from the heme iron binding site.