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). The electrophoretic linear (horizontal) separation of proteins by Ip along a pH gradient in a polyacrylamide gel (also known as isoelectric focusing), followed by a standard molecular weight linear (vertical) separation in a second polyacrylamide gel (SDS-PAGE), constitutes the so called two-dimensional gel electrophoresis or PAGE 2D. This technique allows a thorough separation of proteins as distinct "spots", with proteins of high molecular weight and low Ip migrating to the upper-left part of the bidimensional gel, while proteins with low molecular weight and high Ip locate to the bottom-right region of the same gel.
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) The electrophoretic linear (horizontal) separation of proteins by Ip along a pH gradient in a polyacrylamide gel (also known as isoelectric focusing) followed by a standard molecular weight linear (vertical) separation in a second polyacrylamide gel (SDS-PAGE) constitutes the so called two-dimensional gel electrophoresis or PAGE 2D This technique allows a thorough separation of proteins as distinct "spots" with proteins of high molecular weight and low Ip migrating to the upper-left part of the bidimensional gel while proteins with low molecular weight and high Ip locate to the bottom-right region of the same gel