Antibodies are large proteins with a molecular weight of ~150 kDa. Some antibody classes such as IgMs or IgEs form multimers. Antibodies contain two antigen binding sites (FAB), which bind to antigens with high affinities (Kd values in the nM – pM range). Antibodies also contain a constant region (fragment crystallizable region, Fc). Its recognition by Fc receptors is often investigated. Since antibody dimerization is mediated by disulfide- bonds, Reducing Agents are usually avoided in the assay. In addition, since affinities between antibody and antigen are typically very high, it is recommended to use the Dianthus NT.23Pico or PicoDuo and labeled target concentrations of 1- 5 nM for precise Binding Affinity determination. For antibody antigen assays it is recommended to label the antigen. Alternatively, the antibody can also be labeled. In this case NHS based Protein Labeling of lysine residues with one of the amine reactive labeling kits provided by NanoTemper Technologies is recommended.