Hydrodynamic mobilization

After the proteins are focused in the capillary, the isoforms are mobilized past the detector for UV detection. The mobilization step utilizes either hydrodynamic pressure or chemical means. Chemical mobilization can be performed using either ionic or zwitterionic compounds. The general consensus is that hydrodynamic mobilization results in reduced resolution. Bio-Rad (Hercules, CA) zwitterion cathodic mobilizer with chemical mobilization provides superior resolution (Figure 21). 

FIGURE 21 clEF profile of an antibody using chemical and hydrodynamic mobilization. 

In the following sections, techniques for performing isoelectric focusing in coated or uncoated capillaries in the absence or presence of additives will be discussed. Different electrophoretic and/or hydrodynamic mobilization procedures will also be considered. 

Two-Step Isoelectric Focusing with Hydrodynamic Mobilization... 

Performing hydrodynamic and chemical mobilizations together has been shown to be beneficial for the separation of rhEPO [39] and even necessary for the separation of glycoforms of acidic proteins such as AGP [109] (see Figure 22.12). The addition of phosphoric acid to the catholyte, which consists of sodium hydroxide, at the very beginning of the focusing step promotes chemical mobilization that continues when the pressure is applied at the hydrodynamic mobilization step. 

This relationship is fundamental for the calculation of hydrodynamic properties of colloidal objects (e.g. the terminal settling velocity of small spheres). The factor 6ntja is called friction coefiicient its reciprocal is the hydrodynamic mobility fiy. ... 

Zeta-potential (or electrokinetic potential) electric potential at the shear (or slip) plane within an electric double layer (EDL) the zeta-potential can be measured in case of a relative motion between the charged surface (and Stem layer) and the bulk liquid (including the difluse layer)—e.g. by application of an electric field or due to sedimentation the concept of a slip plane assumes a sharp transition between a stagnant liquid layer attached to the smface and a hydrodynamically mobile liquid phase which is located very close to the outer Helmholtz plane (OHP) the zeta-potential is, therefore, equal or lower in magnitude than the diffuse layer potential at the OHP (cf Sect. 3.1.5.1). 

The injection of charge carriers leads to bulk liquid motion. This effect is also known as electrohydrodynamic motion (EHD). From measurements of the liquid velocity and from calculations of the flow by means of the Navier-Stokes equations it was found that also in the presence of liquid flow. Equation 71 for the SCL currents remains valid (Takashima et al., 1988). The mobility obtained from the slope, however, is the hydrodynamic mobility. For the electrode arrangement — razor blade/plane electrode — the injection current depends on the applied voltage as. 

The phase diagram of the nCB on water is globally compatible with the previous one but with some specific features and a much larger scattering of the points, due to the hydrodynamic mobility of the substrate, and the simultaneous presence of thicknesses f > UB and f < LB. Actually, the UB is defined as the thinnest striped film. Even if many experiments with decreasing average thickness are performed, we cannot prove that the thinnest possible film, that is, the UB, has actually been observed. 

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