[1] Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA
[2] Arizona State Univ, Dept Chem & Biochem, Tempe, AZ 85287 USA
[3] Arizona State Univ, Biodesign Inst, Tempe, AZ 85287 USA
[4] Penn State Univ, Dept Biochem & Mol Biol, University Pk, PA 16802 USA
[5] Penn State Univ, Dept Chem, University Pk, PA 16802 USA