Non-Inerfering Protien Concentration Determination Kit: This kit provides a highly sensitive, colorimetric protein assay that overcomes interference of common laboratory agents present in protein solutions, such as detergents (non-ionic, ionic and zwitterionic), reducing agents (β-mercaptoethanol, DTT), chelating agents (EDTA), amines (Tris), sugars, and strong chaotropic buffers. The kit is suitable for protein concentration determination during protein purification, electrophoresis, and many other protein biology applications. A variety of protein samples can be used from cellular fractions, tissue, 2D lysates to chromatography fractions. In this assay, Precipitation Reagent is added to the protein solution to rapidly precipitate total protein. Interfering agents in the supernatant are discarded. Protein concentration is then determined by mixing the protein with an alkaline solution containing a known concentration of copper salt. The copper ions bind to the peptide backbone and the unbound copper is measured with a colorproducing agent. As the concentration of protein increases, the concentration of unbound copper decreases, thus the color density is inversely proportional to the amount of protein present in solution. This assay is not affected by protein side chains or groups, which minimizes protein-toprotein variation. This fact, when combined with the strategy of removing interfering agents from the protein solution, allows for a highly reliable determination of protein concentration.