Photoinduced Dimerization and Dissociation of Phototropins

From the laser power dependence, the reaction scheme was written as 

From the slop of the plot of k against [LOV], k2 is determined to be 6.6x 105 AI s 1. This value is much smaller than that of the diffusion-limited 

The light-induced dimer should eventually dissociate to return to the monomers, because no permanent change was observed. It may be reasonable to assume that the dimer dissociates when the photoadduct state of LOV2 goes back to the ground state. We should emphasize that this TG technique for the D measurement in the time domain has been the only one technique that can detect such transient dimer formation. 

The temporal profile was again fitted by (8.6). It was found that the signal was reproduced almost perfectly with D of the reactant at the low concentration (Hr = 8.0 x 10-11 m2 s 1), Hi = Hr, H of the product (Dp = 9.8 x 10-11 m2 s-1), and At1 = 300ps. One should note that, from the results of the previous section, H of the dimer and the LOV monomer are 8.0 x 10-11 and 9.8 x 10 11m2s 1, respectively. Therefore, at these concentrated solutions, the reactant existed in a dimeric form and the product is a monomer. The observed TG signal indicated that the dimer was dissociated to yield the monomer with a time constant of 300 ps upon the photoexcitation. The reaction detected by this method is summarized in Fig. 8.13. 

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