In situ AFM and STM of P. aeruginosa azurin on gold lll

Our short overview illustrates some prospects for investigation of metallop-rotein dynamics at metal-solution interfaces. Cyclic voltammetry of small single metalloproteins is straightaway feasible. Reversible electrochemistry can be achieved but molecular detail such as adsorption patterns and precise promoter function remain elusive. 

Investigations of multicentre electrochemical metalloprotein function including metalloenzyme function have also been brought to a level, where both direct and catalytic modes, and elements of molecular mechanisms can be addressed. The latter are, however, entangled by features such as composite electrochemistry, extremely complicated molecular interaction patterns when more than two metallic redox centres are involved, fragile surface enzyme preparations, and lack of structural surface characterization of the adsorbed metalloenzymes. In this respect, two-centre metalloproteins constitute interesting promising intermediates where the coop-erativity between the metallic redox centres can be accurately addressed with molecular resolution within reach. 

Our discussion of scanning probe approaches to metalloproteins at surfaces indicates, first that in situ STM and AFM mapping of metalloproteins with molecular (rather than atomic) resolution is definitely feasible. In addition, submolecular detail is possibly within reach. This is interesting as proteins constitute a class of soft materials. It is also comforting as aqueous solution is otherwise the natural functional medium for proteins. 

Protein mobility and aggregation are inherent problems in the in situ STM and AFM characterization. This can, however, also be turned to the better and brought to open other new perspectives for mapping of molecular and collective protein dynamics such as phase transitions, heterophase fluctuations etc. 

Twenty-first century nanotechnology aspires to endeavour into impressive multidisciplinarity where chemistry, physics, materials science etc., as well as biology and biotechnology are expected to interface. The observations and conclusions above hold intriguing perspectives in these respects. 

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