What is 2D electrophoresis, why is it used in relation to mass spectrometry and what are some pros and cons?

2DE is a technique that is used to separate proteins prior to mass spectrometry. proteins are separated along one axis based on isoelectric point (pH at which the net charge becomes zero) and along a different axis based on molecular weight. proteins of interest can then be 'cut' out and introduced into mass spectrometry. pros: reflects changes in protein expression, isoforms or posttranslational modifications, is able to separate many proteins, inexpensive. cons: time consuming, multiple proteins can remain present in one spot, only detects high abundance proteins, large proteins cannot be seen.