Isoelectric Point


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isoelectric point

[¦ī·sō·i′lek·trik ′pȯint]
(physical chemistry)
The pH value of the dispersion medium of a colloidal suspension at which the colloidal particles do not move in an electric field.

Isoelectric Point

 

(point of zero charge), the state of the surface of a body or of a particle in the dispersed phase in contact with an electrolytic solution; it is characterized by an equal number of positive and negative charges in the adsorption layer. Here the zeta potential is equal to zero. Colloidal systems stabilized by electrolytes are unstable at the isoelectric points—that is, they break down as a result of the adhesion of particles in the dispersed phase. The electrically neutral state of amphoteric electrolytes (ampholytes) that contain separate acid and base groups is also called the isoelectric point. A specific pH value corresponds to the isoelectric point of every ampholyte. At the isoelectric point the molecules of ampholyte, like colloidal particles, lose the ability to shift directionally in an electrical field. The swelling, solubility, and viscosity of solutions and many other characteristics of ampholytes, particularly macromolecular ampholytes, assume extreme values as the isoelectric point is approached.

References in periodicals archive ?
Marchi G, Guilherme LRG, Chang AC, Curi N, Guerreiro MC (2006) Changes in isoelectric point as affected by anion adsorption on two Brazilian Oxisols.
Olaofe O and ET Akintayo Prediction of isoelectric points of legume and oilseed proteins from their amino acid compositions.
pH curves at different ionic strength should intersect at the zeta potential of 0mV, and the intersection pH is the isoelectric point (IEP) (Hunter 1981).
Also, membrane proteins become insoluble if the buffer in which they are analyzed approaches their isoelectric point; therefore, membrane proteins should be separated on one-dimensional gels instead of two-dimensional gels to eliminate separation based on isoelectric point.
Proteins migrate in isoelectric focusing gels to their neutral isoelectric point (pI), where the protein has zero net charge.
Isoelectric Point (IEP) is a numeric value of pH where electrokinetic surface potential equals zero.
Rohm and Haas Company has received a patent for a peelable coating composition that is comprised of an aqueous dispersion of at least one polymer, wherein the polymer has a Tg of greater than zero to 40[degrees] C; at least one amphoteric release agent having an isoelectric point at pH three to pH eight; greater than 0.
One-dimensional and 2-dimensional gel electrophoresis are useful in confirming an inherited dysfibrinogen if the mutation alters the apparent molecular weight or isoelectric point of the A[alpha], B[beta], or [gamma] chain.
Delineating the specific influence of virus isoelectric point and size on virus adsorption and transport through sandy soils.
We have estimated that the basic Arabidopsis leaf peroxidase isoenzyme has an isoelectric point of approximately 9.
These magnetic beads precisely separate proteomic samples based on isoelectric point and net charge differences, in preparation for downstream analyses such as mass spectrometry, HPLC or 1D/2D gel electrophoresis.
Isoelectric focusing separated proteins by their isoelectric point, while SDS gels separated proteins according to molecular weight.