Biotin (Long Arm) Maleimide is designed forBiotinylating proteins, nucleic acids or other molecules containing one or more thiol groups. The presence of the 6-aminohexanoate spacer arm between the maleimide group andBiotin reduces the possibility of steric hinderance. Molecules to be labeled withBiotin (Long Arm) Maleimide require free thiol groups. In the case of proteins,Biotin (Long Arm) Maleimide will react with exposed cysteine residues. Alternatively, free thiols may be generated by reducing disulfide bonds or by modifying other reactive groups such as primary amines with compounds like Traut's reagent (2-iminothiolane). To label nucleic acids, thiols can be introduced into DNA, RNA, or oligonucleotides using specific nucleic acid labeling tools. Due to the very high affinity of avidin and streptavidin toBiotin manyBiotin-avidin/streptavidin systems have been developed making theBiotin label the most suitable for a variety of applications, including in situ hybridization, and Western blotting.Biotin (Long Arm) Maleimide reacts readily under mild acid or neutral pH conditions in aqueous solution with free sulfhydryl groups, such as cysteine residues or sulfhydryls introduced chemically into proteins or other macromolecules. The spacer arm in this derivative insures that theBiotin is fully accessible without steric hinderance to avidin or streptavidin binding and subsequent detection systems.