Once upon a time, I made a couple of "applications" for calculating of
the isoelectric point and the molecular weight of a protein. Both runs
on just about any MacIntosh computer, as they are rather simple!
However, should anyway be interested in obtaining copies of the software,
it may freely be downloaded from my web-page (URL http://www.ed.ac.uk/~lho/).
Inst. of Cell and Mol. Biol.
University of Edinburgh