Scanning Tunnelling Microscopy Images of the Copper-Containing Amine Oxidase from Arthrobacter Globiformis in the Holo and Apo Forms Adsorbed on Gold under Ambient Conditions

Dimeric Arthrobacter globiformis amine oxidase in the holo and apo forms adsorbed onto a Au (111) surface have been observed by scanning tunnelling microscopy (STM) under ambient conditions. Individual protein molecules denature as they adsorb onto a bare Au surface, although they keep a dual appearance. Tapping atomic force microscopy images of individual proteins correspond well with the STM ones in the lateral direction. STM voltage affects the distance between the units of the denatured proteins: negative voltages separate them while positive ones get them together. Disordered as well as ordered layers of apo and holo proteins have been resolved by STM at molecular detail level. Individual proteins lying on the layers present a compact and a distinct dimeric shape, apo dimers looking bigger than holo dimers.