[1] Univ Virginia, Dept Biochem & Mol Genet, Charlottesville, VA 22908 USA
[2] Univ N Carolina, Dept Biochem & Biophys, Chapel Hill, NC 27599 USA
[3] Univ Virginia, Dept Chem, Charlottesville, VA 22908 USA
[4] Univ Virginia, Dept Pathol, Charlottesville, VA 22908 USA