One alternative that has not been mentioned (but that I don't have any
personal experience with yet) is to use carbonyl diimidazole to activate
-OH groups on your resin, for reaction with primary amines in your
protein. I believe the CDI activation has to be done in the absence of
water, but that the immobilization occurs under typical amine-related
conditions (e.g., pH 8 using a non-nucleophilic buffer).
There may also be some carboxylate-based cation exchange resins out there
(e.g., sephadex CM) that you could activate with NHS.
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______________________________________________________________________________
Lou Hom >K'93
lhom at ocf.berkeley.eduhttp://www.ocf.berkeley.edu/~lhom/
