An inorganic, toxic substance with the chemical formula CNBr which is white and crystalline with a sharp odor, is an irritant, and can be dissolved in water, alcohol, and ether. It melts at 52 degrees Celsius and boils at 61.4 degrees Celsius. It is used to extract gold, in pesticides, and in the chemical synthesis of organic substances. It is also used in genetic engineering to cleave polypeptide chains, especially synthetic proteins, wherever the amino acid methionine occurs. It is also used to attach protein ligands to various supporting substances in preparation for affinity chromatography.