[1] Univ Texas Austin, Dept Biomed Engn, Austin, TX 78712 USA
[2] Univ Texas Austin, Dept Phys, Austin, TX 78712 USA
[3] Florida State Univ, Inst Mol Biophys, Tallahassee, FL 32306 USA
[4] Florida State Univ, Dept Chem & Biochem, Tallahassee, FL 32306 USA