Electrophoretic mobility definition

We begin with the definition of electrophoretic mobility, namely, the velocity of a charged particle per unit field strength (Section 12.2). 

The net charge on a protein is the algebraic sum of all its positive and negative charges. There is a specific pH for every protein at which the net charge it carries is zero. This isoelectric pH value, termed the isoelectric point, or pi, is a characteristic physicochemical property of every protein. The definition of pi for molecules as complex as proteins is more or less an operational one and is taken to be that pH at which a protein has zero electrophoretic mobility in an isoelectric focusing run. Nevertheless, it has been shown that the pis of some acidic proteins (up to about pH 7) can be calculated from their amino acid compositions.3 5... 

In sec. 1.6.6a the mobility of individual Ions was discussed. There, the mobility was Introduced as the scalar ratio of the vectors velocity and field strength. This definition also applies to the electrophoretic mobility u, defined through... 

Table 20-3 lists the principal plasma proteins and their half-lives, pi, molecular weights, and preferred method of analysis the individual proteins are listed in the order of their electrophoretic mobilities in agarose gels at pH 8.6. These proteins are described later in this chapter other chapters in this book describe many more proteins enzymes (see Chapter 21) lipoproteins (see Chapter 26) hormones (see Chapter 28) and hemoglobin, fibrinogen, and other coagulation proteins (see Chapter 31). The interim consensus reference intervals for 14 plasma proteins are listed in Table 20-4, pending the publication of more definitive intervals. . 

It is apparent from the above discussion that many hemoglobins with different amino acid substitutions demonstrate identical electrophoretic mobilities. Methods that rely on differences other than net charge are needed to establish the identity of these hemoglobins. Definitive... 

The alkaline phosphatase of both human intestine and placenta are L-phenyl-alanine-sensitive and undergo uncompetitive inhibition to the same extent (nearly 80%) by 0.005 M L-phenylalanine. However, we have been able to find several distinguishing biochemical characteristics of the two enzymes (1) the anodic mobility of intestinal alkaline phosphatase remains unchanged after neuraminidase treatment, whereas the placental enzyme is sialidase-seusitive and hence the electrophoretic mobility on starch gel is considerably reduced by such treatment, (2) the Michaelis constant of placental alkaline phosphatase at a definite pH is appreciably higher than that of the intestinal enzyme (at pH 9.3 the Km values of placenta and intestine are 316 and 160 ixM, respectively), and (3) the pH optima (with 0.018 Af phenyl phosphate as substrate) of the two enzymes are different the values for intestinal and placental enzymes with 0.006 Af n-phenylalanine are 9.9 and 10.6, respectively, and the respective values in the presence of 0.005 Af L-phenylalanine are 10.2 and 11.1. Finally, contrary to the behavior of intestinal alkaline phosphatase, placental enzyme is completely heat stable (P19). 

The electrophoretic mobility depends on the potential and on the shapes and sizes of the particles (see the more detailed discussion in Section 2.4.4). Particles that have the same potentials but different shapes and sizes have different mobilities. In polydispersed colloids with irregular particle shapes, the potential can only be estimated from the electrophoretic mobility, and the result depends on the approach to the definition of the size of an irregularly shaped particles. 

The primary advantage of such an approach is that it creates a flat flow profile, and thus allows definition of precise flow rates and narrow residence time distributions. Nevertheless, electroosmotic flow (EOF) pumps are severely limited in their widespread application to molecular synthesis due to a need for a conductive solvent and the fact that varying electrophoretic mobilities of reagents and products leads to time-dependent concentration gradients within the reactor that can degrade performance. 

Noting that these two forces balance one another, and making use of the definition in Eq. 6, the electrophoretic mobility of long polyelectrolytes is thereby independent of molecular weight... 

Here, (25.149) and (25.154) are chosen for a flow field of a stationary cell. The definition of the electrophoretic mobility of biological cells, /a, is defined by... 

Here, ft is the particle electrophoretic mobility. It should be noted that, whereas Equation 5.74 is valid for a spherical particle satisfying Stokes s law, the definition of p given by Equation 5.75 is more general for large nonspherical particles, other numerical coefficients would appear in Equation 5.73, and for smaller particles and ions, this law losses validity, but always a mobility can be measured. 

The electrophoretic mobility of the cell increases greatly with age, but this variation could not be related to variations in the amount of sialic acid at the surface (see review by Balazs and Jacobson, 1966). During the cell cycle, a definite increase of neuraminidase-susceptible sialic acid was observed by Rosenberg and Einstein (1972) in human lymphoid cells, whereas Kraemer (1967) could not observe this change in osteosarcoma cells. 

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