Congophilicity (Congo red affinity) of different beta(2)-microglobulin conformations characterized by dye affinity capillary electrophoresis

The amyloidogenic protein beta(2)-microglobulin was characterized by affini ty capillary electrophoresis (CE). CE could separate conformational variant s of beta(2)-microglobulin and with the amyloid-specific dye Congo red as a buffer additive it was possible to measure different Congo red-affinities of native and abnormally folded beta(2)-microglobulin, We find that native beta(2)-microglobulin has an intermediate affinity for Congo red at pH 7.3 and that binding involves electrostatic interactions. The conformational va riant of beta(2)-microglobulin that appears in acetonitrile solutions binds Congo red more strongly. Affinity CE using Congo red as a buffer additive is a new, simple, fast, and quantitative micromethod for the characterizati on of soluble conformational intermediates of amyloidogenic proteins. (C) 2 000 Elsevier Science BN. All rights reserved.