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FIGURE 2. Schematic representation of various forms of antibody fragments prepared by enzymatic digestion or molecular engineering. The most commonly used form of antibody, IgG, has been radiolabeled by conjugating directly to the protein (e.g., radioiodination of tyrosine) or radiolabeling a coupled chelator. Chelators have been coupled directly to the protein or to the carbohydrates that reside on the Fc-portion of the molecule. Single chains are formed by linking the variable light (VL) and variable heavy (VH) chains with amino acid (AA) linker. Diabodies, triabodies, and even tetrabodies are formed spontaneously when smaller length AA chains are used to hold the VH and VL units together. Recombinant bispecific diabodies and other bispecific constructs can be prepared by pairing VH and VL of 2 antibodies with different specificities.
