1. Cystic Fibrosis Research and Treatment Center, University of North Carolina, Chapel Hill, NC 27599–7248, USA.
2. Curriculum in Applied Sciences and Engineering, University of North Carolina, Chapel Hill, NC 27599–3280, USA.
3. Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599–7260, USA.
4. Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599–3290, USA.