The magnetic field-induced migration of particles in liquids is a highly-promising technique for the micro-separation analysis of bioparticles, such as cells and large DNA. Here, new methods that make use of magnetophoresis and electromagnetophoresis to induce the migration of microparticles in liquids are briefly reviewed. Magnetic force and Lorentz force are utilized in the new methods. Some typical examples of the use of these methods are described, and the advantages of using a superconducting magnet for them are demonstrated.
The recent development of new migration methods of micro-particles in liquids using various external fields is reviewed. The combination of a laser scattering force and a photothermal effect produced photothermal-conversion laserphotophoresis. A dielectric field generated in a planer or a capillary quadrupole electrode realized dielectrophoresis. Using a micrometer-scaled magnetic field gradient, the "Magnetophoretic velocimetry" of micro-particles was invented. Furthermore, the Lorentz force generated by combining an electric field and a magnetic field was utilized for electromagnetophoresis. These new methods were overlooked and the advantages in analytical use were discussed.
Using the electromagnetophoretic buoyancy for a microparticle in a silica capillary containing an electrolyte solution, the dynamic force dissociation kinetics of the interaction between the mannan polysaccharide on a yeast cell surface and lectins bound to the silica capillary wall have been studied by using the two different modes of the increasing force mode and the constant force mode. Lectins used in the study were concanavalin A (Con A), Hippeastrum hybrid lectin (HHL), Galanthus nivalis lectin (GNL) and Narcissus pseudonarcissus lectin (NPL). The dynamic force measurement by the two different modes gave the spontaneous dissociation rate constant, k(off), of the polysaccharide-lectin binding and the critical increment of bond length at the transition state, Deltax. It was found that the value of k(off) for Con A was the smallest among the lectins studied, due to the strongest binding interaction. It was also confirmed that the magnetophoretic pulling force decreased the transition free energy just like an enzyme.
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