Determination of Inter-Molecular Forces by Magneto-Optical Transmittance of Molecule-Covered Superparamagnetic Particles in Solution

We describe a simple magneto-optical transmittance technique for determining molecular forces between avidin-biotin molecules. The effective length of rotating superparamagnetic chains (SPCs) in a solution determines the amplitude of oscillating transmittance corresponding to the formation of SPCs as described by the Mason number. We propose that the Mason number of SPCs formed via inter-molecular interaction between superparamagnetic beads covered with molecules is modified due to the action of molecular forces. The change in modified Mason number was quickly detected by the change in the amplitude of oscillating transmittance of rotating SPCs in a solution.