Biochemistry Department, National Magnetic Resonance Facility at Madison, University of Wisconsin Madison, Madison, Wisconsin, United States of America. arash@nmrfam.wisc.edu|Biochemistry Department, National Magnetic Resonance Facility at Madison, University of Wisconsin Madison, Madison, Wisconsin, United States of America. arash@nmrfam.wisc.edu|Biochemistry Department, National Magnetic Resonance Facility at Madison, University of Wisconsin Madison, Madison, Wisconsin, United States of America. arash@nmrfam.wisc.edu|Biochemistry Department, National Magnetic Resonance Facility at Madison, University of Wisconsin Madison, Madison, Wisconsin, United States of America. arash@nmrfam.wisc.edu