"Sonicated into solution": really solubilised?

Achim Recktenwald achimr at home.com
Fri Mar 5 19:30:24 EST 1999

Neil Saunders wrote in message <36DF91B6.B5DE0FBD at bio.vu.nl>...
>Dear all,
>Recently I've over-expressed a small protein using pET22b/BL21DE3 and
>have found it to be relatively insoluble (it fractionates with membranes
>after ultracentrifugation).  On resuspension in Tris buffer plus 0.5%
>Triton-X100 I see small brown globules which are also difficult to

Have you checked these globules under a microscope?  They might be micelles
of fats or lipids, something you definitely do not want in your lysate. It
only clogs the chromatographic columns.
Try to remove them by filtration and/or centrifugation?
Or do you perhaps think your protein is in these globules?


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