1. Cranfield Health, Cranfield University, Silsoe, Beds, MK45 4DT, U.K., Biosensors and Biocatalysis Group, Research Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds, LS2 9JT, U.K., and ELISHA Systems Limited, Sigma House, Burlow Road, Buxton, SK17 9JB, U.K.