Figure 2.

(a) Ground state absorption spectra of wild-type MR with and without NADH₄ coenzyme, the features at ∼375 nm, 470 nm, and 550 nm (in the coenzyme bound spectrum) are due to the S₀ → S₂ and S₀ → S₁ transitions, and a charge-transfer band respectively. Example transient absorption difference three-dimensional spectra are shown, after excitation at 375 nm, of wild-type MR (b) without and (c) with NADH₄ coenzyme, the negative absorption feature at ∼470 nm, results from a bleach of the ground state (S₀ → S₁), whereas a positive absorption feature at ∼530 nm originates from excited state absorption (S₁ → S_n). To see this figure in color, go online.