Jj. Regan et al., ELECTRON-TUNNELING IN RU-MODIFIED HIS46ASP AZURIN - COUPLING THROUGH THE CU LIGANDS, Inorganica Chimica Acta, 276(1-2), 1998, pp. 470-480
We compare electron transfer (ET) rates in two chemically modified Pse
udomonas aeruginosa azurins, to examine the role of the Cu ligands in
the ET coupling. In both cases, ET proceeded from Cu+ to a Ru(bpy)(2)(
im)(3+) attached to the native His83.In this otherwise native system,
the Cu+Ru3+ --> Cu2+Ru2+ rate is 1.2(1)x10(6) s(-1) (-Delta G degrees=
0.76 eV) (J.J. Regan, A.J. Di Bilio, R. Langen, L.K. Skov, J.R. Winkle
r, H.B. Gray and J.N. Onuchic, Chem. Biol., 2 (1995) 489 [1]; A.J. Di
Bilio, M.G. Hill, N. Bonander, B.G. Karlsson, R.M. Villahermosa, B.G.
Malmstrom, J.R. Winkler and H.B. Gray, J. Am. Chem. Sec., 119 (1997) 9
921 [2]). In the His46Asp mutant (46 being one of the Cu ligands), the
rate drops to 3.2(4) x 10(4) s(-1) (-Delta G degrees similar to 0.78
eV). Analysis suggests that this drop is primarily due to a disruption
of electronic tube coupling, rather than to just a change in the driv
ing force and/or reorganization energy of the reaction. (C) 1998 Elsev
ier Science S.A. All rights reserved.