Hemocyaninの2,3の性質について(2) : 光散乱による分子量

Abstract

In the previous report we stated that the hemocyanin has been ultracentrifugal purely isolated by means of repetitively isoelectrical precipitation. And we described here the results of light scattering measurements, which have been arranged with Zimm Plotting method. Weight average molecular weight M=164 x 10^4 and dissymmetry coefficient Z=1.22 had been obtained in 0.5 M acetate+ 0.5 M NaCl solution, and over the ionic strength range 0.1～0.2 and pH 5.0～6.2 in acetate buffer it has molecular weight of 60 x 10^4 and Z near unity, also at pH 8.8 with carbonate buffer M=33 x 10^4, Z=1.07. Assuming that the hemocyanin molecule has sphere in shape, the diameter (2 x radius of gyration) of molecules are 97, 50>and 50mμ respectively. We concluded that though solution has had pH near isoelectric point if not higher ionic strength, whole protein was not appeared but only single dissociate. Since at μ=0.1 hemocyanin has consisted of two components, one 63 % and another 37 %, it was found that larger molecule (whole protein) has molecular weight of 240 x 10^4 and smaller 120 x 10^4. The effect of ionic strength to dissociation of hemocyanin was numerously reported by many investigators but concentration dependency of this phenomenon is still not clear. In pH 5.0 curve of light scattering was very similar to insulin solution in low pH range and with dilution of hemocyanin solution associated molecule suffers the splitting into small molecule having one half molecular weight. It seemed that this will be not only characteristic of this hemocyanin sort but universal.