Light scattering in solutions of native and guanidinated rabbit tropomyosin

Abstract 1. 1. The fundamental molecular weight of rabbit tropomyosin has been established by light scattering as 54, 050 ± 1000 at pH 2 and 52, 600 ± 1000 at pH 12. 2. 2. Light scattering measurements have been carried out in the same solvent media as the earlier osmotic pressure work. The aggregation of tropomyosin particles as the ionic strength is diminished is clearly brought out by this technique, the molecular weight increasing from 52, 900 at I= 1.1 to 101, 000 at I= 0.1. These values are about 20% lower than the figures deduced from osmotic pressure and are probably more reliable in view of the lower protein concentrations used. 3. 3. Light scattering measurements have been extended to the ionic strength range below 0.1 where aggregation is most pronounced. The data suggest that up to the hexamer stage the polymerization process is end-to-end. 4. 4. The preparation and characterization of a guanidinated derivative of rabbit tropomyosin by reaction with S-methylisothiorea are described.