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In practice, a protein with an excess of basic aminoacids (arginine, lysine and/or histidine) will bear an isoelectric point roughly greater than 7 (basic), while a protein with an excess of acidic aminoacids (aspartic acid and/or glutamic acid) will often have an isoelectric point lower than 7 (acidic).
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.
The isoionic point is the pH value at which a zwitterion molecule has an equal number of positive and negative charges and no adherent ionic species. 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.
Isoelectric focusing (IEF), also known as electrofocusing, is a technique for separating different charged 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 ...
The isoelectric point of casein is 4.6. Since milk's pH is 6.6, casein has a negative charge in milk. The purified protein is water-insoluble. While it is also insoluble in neutral salt solutions, it is readily dispersible in dilute alkalis and in salt solutions such as aqueous sodium oxalate and sodium acetate.
A mass spectrometer used for high throughput protein analysis. Protein mass spectrometry refers to the application of mass spectrometry to the study of proteins.Mass spectrometry is an important method for the accurate mass determination and characterization of proteins, and a variety of methods and instrumentations have been developed for its many uses.
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 ...
A typical workflow of a peptide mass fingerprinting experiment. Peptide mass fingerprinting (PMF), also known as protein fingerprinting, is an analytical technique for protein identification in which the unknown protein of interest is first cleaved into smaller peptides, whose absolute masses can be accurately measured with a mass spectrometer such as MALDI-TOF or ESI-TOF. [1]