Kinetics and Mechanism of Adsorption

It has become customary to refer to the action of surfaces on proteins as surface denaturation. This is an unfortunate term in some ways. First, it does not satisfy the requirements of a scientific term that needs to be simple and unambiguous. Second, it tends to discourage further interest in the subject whereas, in natural systems, proteins must be continually interacting with interfaces and undergoing changes in conformation and properties. It therefore seems preferable to examine protein adsorption, adhering to strict terminology in order to describe the processes which occur. 

Before a protein molecule can adsorb and exert its influence at a phase boundary or take part in an interfacial reaction, it must arrive at the interface by a diffusion process. If we assume there is no barrier to adsorption other than diffusion, simple diffusion theory may be applied to predict the rate of adsorption. Under these conditions, after formation of a clean interface, all the molecules in the immediate vicinity will be rapidly adsorbed. The protein concentration in a sublayer, adjacent to the interface.and of several molecular diameters in thickness, will thus be depleted to zero. A diffusion process then proceeds from the bulk solution to the sublayer. The rate of adsorption, dn/dt, will be simply equal to the rate of this diffusion step given by classical diffusion theory (Crank, 1956) as 

Equation (4) has been applied to the adsorption, at an air/water interface, of bovine serum albumin (BSA) from solutions of different concentrations (MacRitchie and Alexander, 1963a). The times were measured for monolayers to build up to a surface pressure of 0.1 milli- 

Trumit (1954) has described two closely related methods for determining diffusion coefficients of proteins based on measurement of the rate of adsorption of protein from a dilute solution on to a Blodgett— Langmuir slide. One method employs stirred conditions so that the 

Measured and Calculated Times for Bovine Serum Albumin Films To Reach 0.1 mN m-1 at a Fresh Interface0,11 

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