Four new kits designed to extract proteins from cells and tissues are now available. DUALXtract Mammalian Cell Total Protein Extraction Reagent extracts total protein, while the DUALXtract Nuclear and Cytoplasmic Protein Extraction Kit isolates cytoplasmic and nuclear proteins from cultured cells and tissues. Both are useful with downstream applications such as 1-D and 2-D gel electrophoresis, Western blotting, electrophoretic mobility shift assay, immunoprecipitation, affinity purification, and enzymatic activity and reporter gene assays. The DUALXtract Total Membrane Protein Extraction Kit isolates membrane and cytoplasmic protein fractions from mammalian cells and tissues, without cross-contamination. The DUALXtract Membrane Protein Optimization Kit can be used to identify optimal extraction conditions for membrane proteins of interest and is suitable for the extraction of native, functional membrane proteins from mammalian, fungal, and bacterial cells.