IMMOBILIZED PH GRADIENT AND IEF RUN  Immobilized PH gradients are used for IEF because the fixed PH gradient remain stable ... Preparative and analytical centrifugation von Preparative and analytical centrifugationPratheeba Subramani. 10.1K. views•28 ... which maintains the protein secondary structure and native charge density.  Separation is based upon charge, size, and shape ... Preparative and analytical centrifugation von Pratheeba Subramani. Preparative and analytical centrifugation. Pratheeba ...