I am doing isoelectric focusing on denaturing (6M urea) slab gels. I am looking at two proteins of pI 7 and 6, or so. The upper band (pI 7) is always blurry, not well focused. A complex mixture of proteins shows that all the bands are not well focused in the top 1/3 or so of the gel. Could this be due to heat? What else? Steve Potter UCI Psychobiology Irvine, CA 92717 spotter at darwin.bio.uci.edu