stabilization of purified protein solutions - (Mar/09/2009 )

I have several problems with protein solutions hughly purified, such us aggregation. Any of you could give any tip about agents for stabilization of these kind of solutions?. I am trying: NaCl, DTT, detergent, sugars, pH modification but i am sure there should be quite more.
It would be also very usefull some webpage regarding stabilization of protein solutions, i am looking out for some of them but i have´t found a real good one.
Any suggestions?
Thank you in advance

we used peg-8000 (0.5-5%) to prevent aggregation of some proteases with which we worked.

be careful, higher amounts (~20%) will precipitate proteins and it will co-concentrate with the protein when concentrating by ultrafiltration with a relatively low mw cutoff (10 kDa).

Thank you mdfenko, i will try PEG. For some proteins i have used nearly everything to avoid aggregation in certain conditions
Thank you very much