A sectorial centrifuge cell for swinging bucket rotors--application to a velocity gradient centrifugation methodology

A sectorial cell of 1.55 ml capacity, designed to be used in swinging bucket rotors, is introduced and applied to boundary sedimentation studies. The cell, made of polycarbonate by injection molding, represents an improvement over previously existing models in terms of resistance and attainable speeds. Its use has been extended to polydispersity determination by evaluation of the s value distribution function g(s) = dC/ds. The latter can be corrected to standard conditions (water at 20 degrees C), by using newly derived equations in connection with a cesium sulfate linear density and viscosity gradient which is introduced for boundary stabilization. The cell performance is illustrated with the centrifugal characterization of a polydisperse hyaluronate solution and a paucidisperse proteoglycan A1 preparation. In the latter case a distinctive distribution of aggregates into two polydisperse families of molecules, hitherto not reported in the literature but previously observed with cylindrical cells in this laboratory, has been clearly confirmed. Analysis of plateau dilution during centrifugation indicated absence of artifacts.