iep calculates the isoelectric point of a protein from its amino acid composition assuming that no electrostatic interactions change the propensity for ionization.

Here is a sample session with iep:

% iep sw:laci_ecoli
Output file [laci_ecoli.iep]:

Mandatory qualifiers (bold if not always prompted):

[-sequencea] (seqall)

Sequence database USA.

-graph (xygraph)

Graph type.

-outfile (outfile)

Output filename.

Advanced qualifiers:

-step (float)

pH step value.

-amino (integer)

Number of N-termini.

-[no]termini (boolean)

Include charge at N and C terminus.

-plot (boolean)

Plot charge vs pH.

-[no]report (boolean)

Write results to a file.