Preparation of Economical and Universal Compensation Beads Compatible for Multi-species Antibodies

This protocol describes a cost-effective and reproducible method for preparing multi-species-compatible compensation beads for fluorescence compensation in multicolor flow cytometry. Here, recombinant the immunoglobulin binding protein A/G/L (Protein A/G/L) containing multiple immunoglobulin-binding domains was expressed in Escherichia coli (E. coli), purified using nickel affinity chromatography, and covalently coupled to carboxylated polystyrene microspheres through EDC/NHS chemistry. The resulting beads bind antibodies from diverse species and subclasses, generating strong and distinct fluorescence signals suitable for compensation setup. These results provide practical guidance for selecting bead diameter and protein loading to achieve fluorescence intensities appropriate for different compensation requirements. Successful execution of the protocol is indicated by efficient protein purification and a clear, high-intensity fluorescence peak of conjugated beads compared with control beads during flow cytometry analysis. This simple and scalable approach enables routine preparation of stable, versatile compensation beads in standard laboratories, reducing cost while improving flexibility for flow cytometry applications.