Fe3+ bridging of symmetric mfp-1 films on mica, as measured by the surface forces apparatus. (a) Without Fe3+ there is no interaction after contact. (b) Addition of 10-μM Fe3+ results in an immediate interaction evident by the jump-out peaking at 7 mN m−1.
(c) A 100-min contact increases the interaction to 20 mN m−1. (d) Schematic showing two opposed symmetric mfp-1 films on mica (1) without Fe3+, (2) with 10-μM Fe3+, and (3) with 100-μM Fe3+. Also shown are the suggested chemical interactions between Dopa and Fe3+: (4) no Fe3+, (5) tris-Dopa-Fe3+ complexes, and (6) mono-Dopa-Fe3+ complexes. This research was originally published in Reference 56, copyright © National Academy of Sciences.