Applications of capillary electrophoresis to high-sensitivity analyses of biomolecules

To increase the detection sensitivity of capillary electrophoresis (CE) and thereby widen its application to biomolecular analyses, we have developed a number of on-line preconcentration strategies, i.e., techniques to increase sample loading without compromising resolution and efficiency. Two such techniques, namely, dynamic pH junction and field-enhanced sample injection (FESI) are covered in this work. Dynamic pH junction is predicated on a sharp reduction in an analyte's migration velocity following a reversal of its electrophoretic direction from the acidic sample zone to the basic background solution (BGS) zone. FESI, on the other hand, depends on the retardation of analyte velocity as it transits from the low-conductivity sample zone to the high-conductivity milieu of the BGS zone. Their applications to high-sensitivity analyses of peptides and proteins are discussed.

Separation of Membrane Vesicles and Cytosol from Yeast, Cultured Cells, and Bacteria in a Small Volume Self-Generated Gradient in a Fixed-Angle Rotor

There are many situations when it is necessary to separate rapidly and efficiently a cytosolic and a membrane vesicle fraction from yeast, cultured cells, or from bacteria. This Protocol Article describes the flotation of the vesicles through a self-generated gradient from a dense sample zone using the low-viscosity medium iodixanol. As the sample is exposed to the gmaxthe tendency of the proteins to sediment overcomes any diffusion in the opposite direction and are therefore completely separated from the vesicles.