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. Author manuscript; available in PMC: 2015 May 29.
Published in final edited form as: Phys Chem Chem Phys. 2015 Apr 29;17(18):11933–11949. doi: 10.1039/c4cp05286b

Fig. 15.

Fig. 15

Repair photocycle of (6–4) thymine photoproduct by (6–4) photolyase.27 The resolved elementary steps include a forward electron transfer in 225 ps upon excitation (I to II), a back electron transfer in 50 ps without repair (II to I) and a parallel, catalytic proton transfer between the enzyme (His364) and the substrate (II to III), induced by the initial electron transfer, in 425 ps. This proton transfer is a critical step in repair and determines the overall repair quantum yield. The subsequent repair reactions involve a series of atom arrangements with bond breaking and making (III to IV), and final proton and electron returns (to His364 residue and flavin cofactor) to convert the 6–4PP to two thymine bases on time scales of longer than ten nanoseconds (IV to V).