ULTRACENTRIFUGAL STUDIES ON THE CYTOPLASMIC COMPONENTS

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Abstract
Ultracentrifugal analysis, electron microscopical observation and chemical analysis on the cytoplasmic homogenate of rabbit liver were performed in order to determine the constitution and diversity of the cytoplasmic components. The result of experiments showed that the cytoplasmic components comprised 1) a heterogeneous granular component, sedimented at a rate more than 250s, 2) two closely spaced components whose sedimentation rates were 51s and 64s respectively and 3) three smaller components with rates of 4s, 6s and 12s with regard to the sedimentation analysis. The first heterogeneous granular component showed continuous distribution of size and shape from 50-60 mµ to several µ in diameter and contained three chemical materials, ribonucleic acid, lipids and protein components. The next two closely spaced components, corresponding with considerable numbers of homogeneous micro-particles of about 20 mµ electron microscopically, represented a ribonucleoprotein component in which the RNA:protein ratio was about 1:1.7 and a metalloprotein containing about 20% iron respectively. Accordingly, I must emphasize the need to discriminate these macromolecular components from the heterogenous granular component, including the so-called large granule and small granule fractions, for biochemical Studies on the cell components, and that the cell-fractionation techniques should be improved according to present ultracentrifugal data.
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