EXCITED STATE OF HEME & EFFECTS ON PROTEIN STRUCT BY EXCITATION ENERGY TRANSFER

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We measured the time-resolved emission intensity decay of horse heart myoglobin and tetrameric human hemoglobin under two pulse excitation conditions. The first pulse 580 nm excites the heme (for CO form photodissociate the ligand) and induces a conformational change of hemoprotein structure. The second pulse 290 nm excites tryptophan after a set delay. The tryptophan lifetime distribution measured at given second pulse delay is very sensitive to even small distance changes between tryptophan and heme. By applying the Forster model of radiationless excitation energy transfer between tryptophan and heme we can interpret and follow protein conformational changes from picosecond to a millisecond time range. These studies are only possible because of the core technology project on light quenching at the CFS.