The C6D5.1.1 antibody reacts with biotin (vitamin H, vitamin B7, coenzyme R), a 244.3 Da molecule that is present in all living cells and is essential for cell growth and the citric acid cycle. Biotin is commonly coupled to proteins and other molecules without altering their biological activity for use in a number of applications. Both avidin and streptavidin form strong non-covalent bonds with biotin in a 1:4 ratio and thus efficiently cross-link biotinylated molecules. Both avidin and streptavidin can, however, exhibit nonspecific binding that can be problematic in certain applications. Cross-linking of biotinylated molecules, such as immunoglobulins, can also be achieved using anti-biotin antibodies such as clone C6D5.1.1. This approach may be preferable to eliminate the non-specific binding problems associated with streptavidin, or when a lesser degree of cross-linking is required.