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pi program available

Mark J. Miller mark at alw.nih.gov
Mon Mar 7 13:31:25 EST 1994

A program for calculating the theoretical pI of a protein or
polypeptide has been written by Arthur David Olson of the
Laboratory of Experimental Carcinogenesis, NCI/NIH. It is available
by anonymous ftp to elsie.nci.nih.gov, as pub/pi.shar.gz. The program
is based on the paper by Sillero, A. and J. M. Ribeiro, "Isoelectric
points  of  proteins: theoretical determination,", Anal. Biochem.,
vol. 179, no. 2, pp. 319-25, 1989. The manual and source are included.

Part of the manual page follows:

     pi [ -w ] [ sequence or filename ]

     Pi computes a theoretical isoelectric point for  a  sequence
     using  Sillero and Ribeiro's "abridged" method.  If the com-
     mand line is argument free (or the only  argument  is  "-"),
     the sequence is read from the standard input; if the command
     line has one  argument  that's  the  name  of  a  file,  the
     sequence  is read from the named file; otherwise the command
     line must have one argument which  itself  is  used  as  the

     This option is available:

     -w   Use the weighted mean for pKNa and pKPa values.

     Sillero, A. and J. M. Ribeiro, "Isoelectric points  of  pro-
     teins: theoretical determination," Anal. Biochem., vol. 179,
     no. 2, pp. 319-25, 1989.  The results produced  without  the
     -w  option agree exactly with those in Sillero and Ribeiro's
     paper; the results produced with the option differ (by up to
     0.04  on the sequences given in the paper).  A June 17, 1991
     letter from Prof. Sillero indicates that  the  results  pro-
     duced by the program are correct.

Mark J. Miller                  phone: (301) 496-9343
Building 12A, Room 2033         fax:   (301) 402-2867
National Institutes of Health   Internet: mark at helix.nih.gov
Bethesda, MD 20892

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