HOOK™ Biotin-Hydrazide and its long spacer arm equivalent, HOOK™ Biotin-LC-Hydrazide, are carbohydrate reactive reagents. HOOK™ carbohydrate reactive biotin reagents react with oxidised carbohydrate side chains. Some biotin reagents do not bind directly to the protein itself, but instead, conjugate to the carbohydrate residues of glycoproteins. The carbohydrate reactive biotin reagents contain hydrazides (-NH-NH₂) as a reactive group. The hydrazide reactions require carbonyl groups, such as aldehydes and ketones, which are formed by oxidative treatment of the carbohydrates. Hydrazides react spontaneously with carbonyl groups, forming a stable hydrazone bond. These reagents are particularly suitable for labelling and studying glycosylated proteins, such as antibodies and receptors.