Biotin (Long Arm) Maleimide, 12 mg, is designed for biotinylating proteins, nucleic acids or other molecules containing one or more free thiol groups (cysteine residues or sulfhydryls introduced chemically in proteins or other macromolecules). The 6-aminohexanoate spacer arm reduces steric hindrance, ensuring that biotin is fully accessible to detection systems. In proteins, this product will react with exposed cysteine residues or to free thiols generated by reducing disulfide bonds or modifying other reactive groups, such as primary amines modified with Traut's reagent (2-iminothiolane) or others. In nucleic acids (DNA, RNA, or oligonucleotides), thiols can be introduced using FastTag, 5' EndTag, or 3' EndTag nucleic acid labeling systems. The extraordinary affinity of avidin/streptavidin to biotin makes this label ideal for in situ hybridization, blotting, affinity binding, and more. This product reacts readily under mild acid or neutral pH conditions in aqueous solution.