Appeal No. 2005-1344 Page 14
Application No. 08/468,610
included in appellants’ definition of high ionic strength. We encourage appellants
to clarify this issue.
b. Polarity:
Claim 15 depends from and further limits claim 1 to require that the
electrostatic charge induced on the resin of the resin-protein/peptide complex is
of the opposite polarity from the net electrostatic charge on the target protein or
peptide at the pH of desorption. According to appellants (Brief, page 9),
Boardman teaches that cytochrome c is desorbed from the resin at a pH where
both Amberlite IRC 50® and cytochrome c have net negative charges. As we
understand it, this statement is incorrect. We believe it to be a well known
biochemical principal that at a pH below its pI a protein will carry a net positive
charge, and at a pH above its pI a protein will carry a net negative charge.
Boardman teaches that the pI of cytochrome c is 10.1. Boardman, page 209,
first column, third full paragraph. According to Boardman “[c]ytochrome c
(isoelectric point 10.1) is desorbed … as the pH rises from 8 to 10, but is not
desorbed under acidic conditions.” Id. A pH from 8-10, is below the pI of
cytochrome c, accordingly it appears that while the Amberlite IRC 50® will exhibit
a net negative charge at this pH, cytochrome c will have a net positive charge.
Thus, the desorbing solution taught by Boardman for use in eluting cytochrome c
has a pH which induces an electrostatic charge on the resin wherein the induced
charge is of the opposite polarity as the net charge on the target protein or
peptide at the pH of the desorbing solution. Thus, it would appear that the
electrostatic charge induced on the resin of the resin-cytochrome c complex is of
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