(Top panel) NE-Asc complex formation. Separate injections of NE and Asc produce single peaks. A new peak appears when they are mixed and injected together. The * indicates free NE. (Bottom panel) Electric field dependence of NE-Asc binding. Data points and best fit lines for the titration of 1.0 mM NE by Asc at different electric fields. At greater electric fields, more Asc is needed to saturate NE. The KEs for 102, 128, 153, 179, and 204 V/cm are 1.1, 2.6, 8.3, 14.8, and 32.4 mM, respectively.