1. Department of ChemistryUniversity of California, San DiegoLa JollaCalifornia92093USA
2. Department of ChemistryMassachusetts Institute of TechnologyCambridgeMassachusetts02139USA
3. Department of Biological ChemistryUniversity of CaliforniaIrvineCalifornia92717USA
4. Department of BiochemistryBrandeis UniversityWalthamMassachusetts02154USA
5. Department of ChemistryImperial CollegeLondonSW7 2AYEngland