Diffusion Detection of Interprotein Interaction

In the previous sections, several examples were reviewed to show that the diffusion change is sensitive enough for the detection of the protein-protein interaction. This method could be called the diffusion detected biosensor method. Characteristic features of this method are discussed in the following. 

Second, not only protein-protein interaction but any intermolecular interaction that changes D can be detected. Protein association changes the radius of the diffusing species, which leads the changes in D. However, I) is determined not only by these factors, but also by the conformation of the protein or the intermolecular interaction. This is a characteristic compared to the SPR method, in which a refractive index change by the association is necessary. Since the small molecular binding to a protein may not change the refractive index, this process should be silent for the SPR method. 

compared with the SPR method, it is a big advantage that the target protein need not be fixed on a metal surface. The intermolecular interaction can be detected in the solution phase. Hence this method can be used conveniently without pretreatment of the sample, such as fixing on a metal 

Fourth, since the diffusion coefficient is not sensitive to the temperature fluctuation during the measurement, a precise temperature control is not required. This merit may be very useful compared with the SPR technique, which is very sensitive to the temperature so that the sample temperature should be kept constant precisely during the measurement. 

solvent properties do not affect the measurement by this system at all. Hence, solvent can be changed without any limitation. This is also an advantage over the SPR method, in which the refractive index of the solvent is an important property for the experiment. 

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