protein homology search

[paul betts]

Does anyone out there know of a database, or software to search a protein
sequence database, or any other strategy that will allow a search based on
protein molecular weight and/or pI?  I am aware of e-mail available
searches of the products of proteolytic digests but not of anything for
whole proteins.  There is a rumor here that such a database access exists. 
It would be, perhaps, useful in the analysis of 2-D gel spots.