Adjusting the pH of an aqueous protein solution to the point where the numbers of positive and negative charges on the protein are equal brings the protein to its isoelectric point. This is often the point of lowest solubility, presumably because it is the point at which there are fewest intermolecular repulsions, so that the molecules tend to form aggregates.
The application can make a plot of the ionization curve with respect to pH and can write an output file of the data.
|
iep
reads in any protein sequence USA.
For each pH point it gives the number of bound electrons and the charge.
Here is the default Epk.dat file:
# pK values for amino acids # O=Ornithine J=Hydroxyproline # # Amino acid pK Amino 8.6 Carboxyl 3.6 C 8.5 D 3.9 E 4.1 H 6.5 K 10.8 R 12.5 Y 10.1