First-Principles Theory of Muon and Muonium Trapping in the Protein Chain of Cytochrome c and Associated Hyperfine Interactions

R. H. Scheicher1, D. Cammarere1,2, T. M. Briere3, N. Sahoo1,4, T. P. Das1, F. L. Pratt5, K. Nagamine3,6

1 Department of Physics, State University of New York at Albany, Albany, New York, 12222, USA
2 Tamarac High School, Brittenkill, New York, USA
3 Meson Science Laboratory, High Energy Accelerator Research Organization (KEK), Tsukuba Shi, Ibaraki, 305, Japan
4 Department of Radiation Oncology, Albany Medical College, Albany, New York, 12208, USA
5 RIKEN-RAL, Didcot, UK; Clarendon Laboratory, Oxford, UK
6 Muon Science Laboratory, Institute for Physical and Chemical Research (RIKEN), Wako Shi, Saitama, 351-01, Japan

The microscopic details of the electron transfer in Cytochrome c are being investigated by the Muon Spin Rotation (mSR) technique [1] in which a muon (m+) is used to probe the moving electron by spin-lattice relaxation in mSR produced by the fluctuating hyperfine field due to the electron. We are using the Hartree-Fock Cluster Procedure to determine the most likely trapping sites for m+ and muonium (Mu) in the protein chain, and have performed [2] extensive calculations in single amino-acid molecules, homopolypeptides (polyglycine) and heteropolypeptides (protein chain of Cyt c). The double-bonded oxygen atom of the carboxyl group was identified as the trapping site for both m+ and Mu. Utilizing the wave-functions we obtained from the Hartree-Fock calculations, we have determined the hyperfine field that the m+ in Mu experiences while the latter is trapped and also the field at the m+ at different positions of the electron after leaving the trapped Mu.

[1] K. Nagamine et al., RIKEN Rev. 20, 51 (1999)
[2] R. H. Scheicher et al., Bull. Am. Phys. Soc., 45, No. 1, 260 (2000)

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