We got a very low MSR when we biotinylated our antibody. Suggestions?

One thing to try is to reduce the antibody concentration to around 1 mg/mL and use 20 equivalents of ChromaLink™ Biotin. This should help improve or increase the MSR. If a precipitate is observed, you may be experiencing another situation. Some antibodies are very sensitive to lysine modification—this could be one of them. Charges are being removed when lysine residues are modified, thereby affecting solubility of the protein.