First-principle determination of muon and muonium trapping sites in horse heart cytochrome c and investigation of magnetic hyperfine properties

The trapping of the muon in the heme unit and of the muon and muonium in am ino acids on the protein chain in horse heart cytochrome c are studied usin g the Hartree-Fock-Roothaan procedure for the interpretation of resonance d ata from mu SR experiments. For the heme unit, trapping of the muon has bee n found at the nitrogen of the pyrrole ring with an expected mu SR shift of 88.4 ppm. For the amino acids on the protein chain, studies of cystein, ly sine and alanine show that the muon attaches itself to all atoms carrying n egative effective charges including the oxygen of the C=O group which exist s in all amino acids, the oxygen and carbon trapping the muonium through th e break up of the re bond between them. (C) 2000 Elsevier Science B.V. All rights reserved.