biopython v1.71.0 Bio.SeqUtils.IsoelectricPoint
Calculate isoelectric points of polypeptides using methods of Bjellqvist.
pK values and the methos are taken from::
* Bjellqvist, B.,Hughes, G.J., Pasquali, Ch., Paquet, N., Ravier, F., Sanchez, J.-Ch., Frutiger, S. & Hochstrasser, D.F. The focusing positions of polypeptides in immobilized pH gradients can be predicted from their amino acid sequences. Electrophoresis 1993, 14, 1023-1031. * Bjellqvist, B., Basse, B., Olsen, E. and Celis, J.E. Reference points for comparisons of two-dimensional maps of proteins from different human cell types defined in a pH scale where isoelectric points correlate with polypeptide compositions. Electrophoresis 1994, 15, 529-539.
I designed the algorithm according to a note by David L. Tabb, available at: http://fields.scripps.edu/DTASelect/20010710-pI-Algorithm.pdf