The Cydex Blue Assay: A One-Step Protein Assay for Samples Prior to SDS Electrophoresis

Determination of protein concentrations prior to (sodium dodecyl sulfate) SDS electrophoresis is made difficult by the simultaneous presence of SDS and reducers in the buffers used for protein extraction. Reducers interfere with the copper-based assays, while SDS interferes with the dye-binding assays. The combined use of cyclodextrins with a commercial Bradford reagent concentrate, described in this chapter, allows to determine protein concentrations in a Laemmli-type buffer, containing both SDS and reducers, in a single step (without any precipitation) with a simple spectrophotometric assay. The use of various cyclodextrins brings compatibility not only with SDS but also with other nonionic and ionic detergents such as sodium deoxycholate or detergents of the Triton type.