Sodium bicinchoninate is a Cu(I)- specific colorimetric reagent that is more sensitive than neocuproine. Its absorption maximum is at 562 nm (molar absorptivity: 7,900). In alkaline solution, Cu(II) is reduced by proteins to Cu(I), and then forms a purple complex with Sodium bicinchoninate. The protein detection range of this assay is 1-2,000 mg per ml.
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