1. School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U.K.
2. School of Electronic and Electrical Engineering and Pollard Institute, University of Leeds, Leeds LS2 9JT, U.K.
3. Bragg Centre for Materials Research, University of Leeds, Leeds LS2 9JT, U.K.
4. Department of Chemistry & Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States