Plastocyanin self-exchange rate constants

Blue copper proteins, 36 323, 377-378, see also Azurin Plastocyanin active site protonations, 36 396-398 charge, 36 398-401 classification, 36 378-379 comparison with rubredoxin, 36 404 coordinated amino acid spacing, 36 399 cucumber basic protein, 36 390 electron transfer routes, 36 403-404 electron transport, 36 378 EXAFS studies, 36 390-391 functional role, 36 382-383 occurrence, 36 379-382 properties, 36 380 pseudoazurin, 36 389-390 reduction potentials, 36 393-396 self-exchange rate constants, 36 401-403 UV-VIS spectra, 36 391-393 Blue species... 

Fe "-OOH (ES) complex, 43 95-97 heme-bound CO, 43 115 lock-and-key model, 43 106-107 mutation in proximal heme cavity, 43 98 residue location, 43 101-102 van der Waals surfaces, 43 112-113 Velcro model, 43 107 zinc-substituted, 43 110-111 plastocyanin, cross-linked, cyclic voltammogram, 36 357-358 promoters, 36 345-346 protein-electrode complex, 36 345, 347 redox potential, 36 349 self-exchange rate constants, 36 402 stability at electrode/electrolyle interface, 36 349-350... 

Unfortunately, experimental kn values are not available for any one of the three blue proteins. It has been established, however, that the self-exchange rates for azurin (24) and plastocyanin (25) are both slow on the NMR time scale at 25°. It is not likely that the predicted kn values from the Fe(EDTA)2 reactions will correspond to the measured self-exchange rate constants. Indeed, agreement between calculated and measured kn values is only to be expected if the activation requirements of both partners in a cross reaction are exactly the same as those used in their respective self-exchanges. Access to a buried, or at best partially exposed, outer-sphere redox center should vary substantially for different reactants, and it is likely that calculated kn values will span a wide range in such cases. 

Cross reactions of plastocyanins and azurins from various sources with cytochromes can be fitted to the Marcus equation using constant self-exchange rate constants of 6.6 x 10 s for the plastocyanins, 9.9 x 10 s for Ps. 

---