Yphantis centerpiece

Figure 2. Plot of the cross-sectional width f(r) vs. radial distance r for an Yphantis centerpiece...

When the Yphantis centerpiece is used, the analog of Equation 32 is... 

The method of equilibrium ultracentrifugation described by Yphantis (28) was used in these studies. A double-sector centerpiece with two 2 1/2° sectors 12 mm. in length was used with standard Schlieren optics. Apparent molecular weights, M, were determined from the equation ... 

So far the equations that have been developed are independent of the shape of the cell. In order to make Equation 17 more useful, it is necessary to relate Ci( — 0) to the initial concentration of component i, Coi. To do this one applies conservation of mass, which states that in a closed system (the solution column in the ultracentrifuge cell) the total amount of solute is constant at all times. Since mass equals concentration times volume, it is necessary to know the volume of the centerpiece, and this depends on the shape of the centerpiece. Two types of centerpieces are currently used. One is a sector-shaped centerpiece, and the other is a six-channel, equilibrium [or Yphantis (24)] centerpiece. Top views of both centerpieces are shown in Figure 1. In either centerpiece, one side is reserved for solvent and the other for solution. 

Figure 1. Top view of double-sector (left) and Yphantis (right) centerpieces...

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