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The isoelectric point (pI, pH(I), IEP), is the pH at which a molecule carries no net electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I). [1] However, pI is also used. [2] For brevity, this article uses pI.
[72] [73] [74] The isoelectric point of a given molecule is a function of its pK values, so different molecules have different isoelectric points. This permits a technique called isoelectric focusing , [ 75 ] which is used for separation of proteins by 2-D gel polyacrylamide gel electrophoresis .
[3] [4] Hen egg white lysozyme is thermally stable, with a melting point reaching up to 72 °C at pH 5.0. [5] However, lysozyme in human milk loses activity very quickly at that temperature. [6] Hen egg white lysozyme maintains its activity in a large range of pH (6–9). [7] Its isoelectric point is 11.35. [8]
The two dimensions that proteins are separated into using this technique can be isoelectric point, protein complex mass in the native state, or protein mass. [citation needed] The separation by isoelectric point is called isoelectric focusing. Thereby, a pH gradient is applied to a gel and an electric potential is applied across the gel, making ...
Serine (symbol Ser or S) [3] [4] is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − NH + 3 form under biological conditions), a carboxyl group (which is in the deprotonated − COO −
The iso-electric point is the pH value at which the zeta potential is approximately zero. At a pH near the iso-electric point (± 2 pH units), colloids are usually unstable; the particles tend to coagulate or flocculate. Such titrations use acids or bases as titration reagents. Tables of iso-electric points for different materials are available ...
At the isoelectric point the relationship between the dielectric constant and protein solubility is given by: log S = k / e 2 + log S 0 {\displaystyle \log S=k/e^{2}+\log S^{0}\,} S 0 is an extrapolated value of S , e is the dielectric constant of the mixture and k is a constant that relates to the dielectric constant of water.
Polyethylenimine (PEI) or polyaziridine is a polymer with repeating units composed of the amine group and two carbon aliphatic CH 2 CH 2 spacers. Linear polyethyleneimines contain all secondary amines, in contrast to branched PEIs which contain primary, secondary and tertiary amino groups.