Figure 6.

In situ STM image of preadsorbed P. aeruginosa azurin on gold(111) (50 mM ammonium acetate, pH 4.65). Tunnel current = 2 nA. Substrate potential = −400 mV (Au/AuO_x) or +450 mV (SCE). Bias voltage = 400 mV. Each of the small structures corresponds in size to the crystallographic molecular adsorbate dimension, and the image is indicative of the formation of a highly ordered array of adsorbed azurin molecules. Each molecular-size structure also exhibits a central submolecular feature of brighter contrast, indicative of higher tunneling conductivity through this part of the molecule (cf. Fig. 7). A triangular gold(111) terrace is visible under the adsorbate layer.