Bio-rad Laboratories, Inc.

Jia-li Liao

Christopher J Siebert

Stellan Hjerten

Rong Zhang

The present invention provides new methods for the concentration of ionic solutes, particularly ampholytes, such as, for example, peptides, proteins and nucleic acids. The methods are based on the fact that the electrophoretic migration velocities of solutes decrease upon a decrease in the absolute value of the zeta-potential of a solute or the pore size of the electrophoresis medium, and upon an increase in the cross-section of the electrophoresis chamber, the viscosity of the electrophoresis medium, or the electrical conductivity of the electrophoresis medium. When applied to capillary electrophoresis, the methods described herein permit concentration of a solution of solutes in the same capillary tube as is used for the electrophoretic analysis. Alternatively, however, the sample can be withdrawn from the capillary tube following concentration of the solution of solutes and processed by techniques other than high-performance capillary electrophoresis (HPCE).

Concentration of biological samples on a microliter scale and analysis

The present invention provides new methods for desalting samples of ionic polymers or weak electrolytes, preferable ampholytes (e.g., peptides, proteins and glycoconjugates) or, compounds which can be transformed into these substances by complex formation. The methods of the present invention are based on the fact that salts can be removed from a sample by electrophoretically replacing the salts with ampholytes present in the ampholytic media of the anolyte and the catholyte or, with displacing cations and anions that have been introduced into the anolyte and catholyte, respectively, and which have mobilities less than the mobilities of the cations and anions to be removed from the sample. Although applicable to both small-volume and large-volume samples, the methods are particularly well suited for small-volume samples. Moreover, when applied to capillary electrophoresis, the methods described herein permit desalting of a sample in the same capillary tube as is used for the electrophoretic analysis. Alternatively, however, the sample can be withdrawn from the capillary tube following desalting and processed by techniques other than high-performance capillary electrophoresis (HPCE). Regardless of which method is used, the desalting methods of the present invention are rapid, highly reproducible, and they give a high recovery of sample compared to dialysis.

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Upsala, Sweden

Jia-li Liao