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pICalculax — Isoelectric point (pI) predictor for chemically modified peptides and proteins; SWISS-2DPAGE Archived 2016-12-10 at the Wayback Machine — a database of isoelectric points coming from two-dimensional polyacrylamide gel electrophoresis (~ 2,000 proteins) PIP-DB — a Protein Isoelectric Point database (~ 5,000 proteins)
The isoelectric point (pI) is the pH of a solution at which the net primary charge of a protein becomes zero. At a solution pH that is above the pI the surface of the protein is predominantly negatively charged and therefore like-charged molecules will exhibit repulsive forces.
When a protein folds, the titratable amino acids in the protein are transferred from a solution-like environment to an environment determined by the 3-dimensional structure of the protein. For example, in an unfolded protein, an aspartic acid typically is in an environment which exposes the titratable side chain to water.
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 ...
This differential scale has two comparative advantages: (1) it is especially useful for treating changes in water-protein interactions that are too small to be accessible to conventional force-field calculations, and (2) for homologous structures, it can yield correlations with changes in properties from mutations in the amino acid sequences ...
It was first defined by S.P.L. Sørensen, Kaj Ulrik Linderstrøm-Lang and Ellen Lund in 1926 [1] and is mainly a term used in protein sciences. It is different from the isoelectric point (pI) in that pI is the pH value at which the net charge of the molecule, including bound ions is zero. Whereas the isoionic point is at net charge zero in a ...
The pzc is the same as the isoelectric point (iep) if there is no adsorption of other ions than the potential determining H + /OH − at the surface [clarification needed]. [8] This is often the case for pure ("pristine surface") oxides in suspension in water. In the presence of specific adsorption, pzc and isoelectric point generally have ...
Isoelectric focusing (IEF), also known as electrofocusing, is a technique for separating different molecules by differences in their isoelectric point (pI). [ 1 ] [ 2 ] It is a type of zone electrophoresis usually performed on proteins in a gel that takes advantage of the fact that overall charge on the molecule of interest is a function of the ...