The magnetic field induced birefringence in isotropic aqueous suspensions of tobacco mosaic virus (TMV) was measured as a function of temperature and concentration in high magnetic fields (100 kG). The temperature range was between 15 and 50thinsp;deg;C and the concentration range was between 4 and 20 mg/cm3. We find that the Cottonndash;Mouton constant (C) increases with decreasing temperature by 15percnt;ndash;20percnt; over the entire range and extrapolates to infinity at a finite temperature of 110 to 150 K. At constant temperature, the measured rgr;/C(rgr;=number of TMV particles per cm3of suspension) can be expanded in a power series of rgr;, where the coefficients are expressed by the irreducible cluster integrals. At 20thinsp;deg;C the experimental values can be fitted to the linear form: rgr;/lgr;C=(2.09times;1030ndash;1.35times;1015rgr;)G2/cm3. For rigid cylindrical particles withl=3000 Aring; andd=180 Aring;, and using the rigid hard particle interaction model, we find for the first order coefficient 0.62times;1015, i.e., a significant deviation for the rigid hardhyphen;rod model. This deviation is also indicated by the variation ofCwith temperature. We discuss the results on TMV and of similar measurements on phagefdin terms of the interparticle interaction and rigidity of the particles.
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