Isoelectric Point

last updated by

biotechatrocketmail 16 years ago

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- November 29, 2007 at 2:12 am #8675
  rikajaj
  Participant
  Can someone tell me how to find the theoretical isoelectric point of a given protein? Is there an equation? Or a search tool? I tried pubmed but I couldn’t find it for the protein I need to do a paper on.
  Thanks
- November 29, 2007 at 2:57 am #78685
  mith
  Participant
  http://www.expasy.ch/tools/pi_tool.html
  this is a predictor….
- November 29, 2007 at 8:06 pm #78720
  MrMistery
  Participant
  I am no expert, but an isoelectric point determination program should work with PDB files, as you need to know its 3D shape. It doesn’t matter so much what aminoacids are in the protein, but rather what aminoacids are on the surface…
- November 30, 2007 at 2:12 am #78732
  woolleyy
  Participant
  As I understood it a Pi detector was pretty shabby, as nothing can really substitute for hard evidence from a little experimenting…
- December 1, 2007 at 6:44 pm #78814
  MrMistery
  Participant
  I would think a program that would work with PDB files should get them pretty close, as it could take into account all the aminoacids on the surface. Sure, nothing beats a good isoelectric focusing, but it is good for a start.
  However, i don’t know if such a program exists…
- November 19, 2008 at 9:42 am #87265
  biotechatrocketmail
  Participant
  There is Henderson–Hasselbalch equation which you can use to calculate raw IP of protein (see http://en.wikipedia.org/wiki/Henderson% … h_equation). The other problem is estimation of pK values. More info about this you can find on http://isoelectric.ovh.org/ There you will be able to calculate IP for given sequence using different pKs or download all PDB database with calculated isoelectric points.
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