<sup>1</sup>H NMR studies of Cr(NH<inf>3</inf>)<inf>6</inf><sup>3+</sup> binding to spinach plastocyanin
Armstrong FA., Driscoll PC., Hill HAO., Redfield C.
All the aromatic and most of the methyl group resonances in the 1H NMR spectrum of Cu(I) spinach plastocyanin have been assigned. The binding of the paramagnetic cation Cr(NH3)63+ to the protein has been investigated by both one- and two-dimensional NMR techniques. This relaxation probe causes the broadening of several resonances in the aliphatic region of the spectrum corresponding to spatially separated groups, thus reflecting a large Cr(NH3)63+ -accessible surface. Three groups of negatively charged residues are tentatively assigned as cation binding "sites" on the protein surface. © 1986.