Analytical ultracentrifugation sedimentation rate

Where S is the sedimentation coefficient of the particle at an adjusted pH, S0 is the sedimentation coefficient of the unswollen particle (low pH), r is the unswollen particle radius, and x is the increase in radius of the swollen particle. In this study, the model latexes were diluted with distilled water to 1 percent solids by weight. Individual samples were adjusted to various pH values with sodium hydroxide and allowed to equilibrate for at least 24 hours. Sedimentation rates were obtained at 30°C using a Beckman Model E analytical ultracentrifuge. 

EXAMPLE 7.17 Ribosomal RNA in eukaryotes is actually four separate RNA species 28S RNA, 18S RNA, 5.8S RNA, and 5S RNA. (The S notation is related to how fast a molecule sediments in an analytical ultracentrifuge cell.) The larger the number, the faster the sedimentation rate. A globular protein of 100 kDa has an S value of 6S, but note that the relationship between size and S value is a sublinear one see Chap. 4. The 28S, 18S, and 5.8S rRNAs are transcribed as long precursor pre-rRNAs of size 45S. 

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