Some observations on the behaviour of proteins at solid-liquid interfaces

In this chapter, we overview first some recent examples of interfacial electrochemical ET of composite metalloproteins where molecular mechanistic detail has in some way been achieved. We discuss next some theoretical issues regarding in situ STM of large molecules, where resonance or environmentally activated tunnel channels are opened by the redox metal centre. This is followed by an overview of some recent achievements in the area of in situ STM/AFM of the single-metal proteins cytochrome c and azurin on polycrystalline and single-crystal platinum and gold surfaces. Such an integrated approach offers new perspectives for experimental and theoretical characterization of metalloproteins at solid surfaces in contact with the natural aqueous medium for metalloprotein function. 

2 SOME OBSERVATIONS ON THE BEHAVIOUR OF PROTEINS AT SOLID-LIQUID INTERFACES 

Protein function at solid-liquid interfaces holds a structural and a dynamic perspective [31]. The structural perspective addresses macroscopic adsorption, molecular interactions between the protein and the surface, collective interactions between the individual adsorbed protein molecules, and changes in the conformational and hydration states of the protein molecules induced by these physical interactions. Interactions caused by protein adsorption are mostly non-covalent but strong enough to cause drastic functional transformations. All these features are, moreover, affected by the double layer and the electrode potential at electrochemical interfaces. Factors that determine protein adsorption patterns have been discussed in detail recently, both in the broad context of solute proteins at solid surfaces [31], and in specific contexts of interfacial metalloprotein electrochemistry [34]. Some important elements that can also be modelled in suitable detail would be  

Such controlling factors are matched by complementary properties of the solid surface, i.e., the hydrophobic or hydrophilic surface character, porosity and topology, charge, hydration, and the presence and composition of surface groups. Particularly for electrochemical surfaces intrinsic catalytic reactivity of the surface groups formed spontaneously or by po-tentiostatic control also follow. Both in the context of electrochemical protein reactivity, and in the broader areas of proteins at surfaces, surface control and modification to structural and functional compatibility with the proteins are key issues. The use of electrochemical promoters, illustrated below, is one such example [32-34]. 

---

Some observations on the behaviour of proteins at solid-liquid interfaces 135... 

---