Electrophoresis size ratio

Thus, electrophoresis commonly measures size/charge ratios of migrating molecules (or, better, charge/size ratios (z/dft). The Stokes diameter of a protein [nm] is related to the molar mass Mr [g moh1] by Eq. (9.17). 

The follow-up section will deal with separation methods based upon (a) molecular size and related to it hydrodynamic volume (size-exclusion chromatography and ultrafiltration), (b) molecular size and related to it molecular diffusivity (field-flow fractionation), and (c) charge/size ratio and related to it molecular polarity (electrophoresis and mass spectrometry). Also reviewed will be hyphenated techniques or those that combine separation by chromatography or electrophoresis with spectral detection. 

Capillary zone electrophoresis (CZE), Charge-to-size ratio Proteins and peptides, peptide mapping, glycoproteins, monoclonal antibodies, carbohydrates and oligosaccharides... 

A number of separation modes are possible. In native gel electrophoresis, charged analytes are distinguished according to their apparent mobility, Papp, and size. In sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analytes are treated such that they all exhibit the same charge to size ratio. Hence, they are separated only by differences in their size. This method can be used for... 

In AE the analyte interacts during electrophoresis with a ligand that may be either in a bovmd or in a soluble state. Generally the complexation of interacting molecular partners will lead to a change in the net charge-to-size ratio. Thus in free solution the com-plexed macromolecule will have an electrophoretic mobility different from that of the free (or... 

In electrophoretic separation techniques, as opposed to the chromatographic techniques, there is no mobile phase or stationary phase. In zone electrophoresis (a kinetic process), the migration length (L = u-t) is proportional to the applied voltage (u=ju E) and time, and separation of analytes with different charge/size ratio (q/tj is obtained. 

Capillary electrophoresis (CE) either coupled to MS or to laser-induced fluorescence (LIF) is less often used in metabolomics approaches. This method is faster than the others and needs a smaller sample size, thereby making it especially interesting for single cell analysis [215] The most sensitive mass spectrometers are the Orbitrap and Fourier transform ion cyclotron resonance (FT-ICR) MS [213]. These machines determine the mass-to-charge ratio of a metabolite so accurate that its empirical formula can be predicted, making them the techniques of choice for the identification of unknown peaks. 

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