Aggregation of membrane proteins

[Dayanidhi Raman]

Hi, I am trying to purify a membrane protein using antibody affinity chromatography.  After elution I test them on SDS-PAGE and silver stain them to check for  purity.  But the proteins seems to aggregate & never enters the stacking gel.   If at all it enters into the separating gel it runs a little high than where it is supposed to be.  I do have detergent (nonionic) in the elution buffer.  Does anybody had a similar problem & know how to troubleshoot?.