The1H,14N, and63.65Cu electron nuclear double resonances (ENDOR) of stellacyanin have been measured. This represents the first published observation of copper ENDOR in a protein. In confirmation of the results of Rist et al., the cupric ion must have a minimum of two nitrogenous ligands. The Cu hyperfine splitting (hfs) tensor and the quadrupole tensor have been determined, the first such complete characterization for a copper protein. The unusual Cu hyperfine tensor can be explained by assuming a flattened tetrahedral geometry, without assumption as to the nature of the coordinated ligands; the observation of large quadrupole couplings also appears to be an effect of geometry. The coordination of Cu in stellacyanin is discussed in terms of these results.
ASJC Scopus subject areas
- Colloid and Surface Chemistry