So you did a lot of work and you have managed to engineer an antibody for your purpose. You do an Elisa assay and BLI or SPR to check for binding to your target. However, you do not know where it binds to in the antigen and which residues in the CDR loops are responsible. The obvious solution is to cryo em or negative stain or crystalize your antibody with your antigen. But what if you can not. What if your antibody is thermally unstable (which is normally not a problem however have encountered this). What if your lab does not have the money to pay for synchrotron time or the cryo em machine time. What if you can not get a colaborator. What if you simply do not have the time. What do you do then? The solution to the question is to do the exact same experiment but computationally. There are many programs that can easily fold the structure of Antibodies given the amino acid sequence in a .fasta file since the barrel-shaped portions of antibodies are usually conserved and only the CDR loops must be correctly modeled. Some of these programs are igfold, alphafold, rosettafold, and rosettaAntibody. If the Antigen is not available in a crystal structure a homology model can be made using alphafold however more caution must be used with homology models. With the current computational software, it is possible to find where your antibody binds to an antigen and depending on what you use, it can be done within an hour.