OpenSPR™ is a powerful instrument providing in-depth label-free binding kinetics for a variety of different molecular interactions. One of the most common methods of antibody immobilization is through the use of Protein A. Protein A is a protein that will bind to the Fc region of many antibody isoforms. The advantage of Protein A facilitated antibody immobilization is that the orientation of their epitope binding regions is projected outward from the sensor surface, which will guarantee their availability for analyte binding. When antibodies are immobilized directly to a sensor via amine coupling, much of the binding availability may be limited due to improper orientation of the antibody. Nicoya Lifesciences has created a Protein A kit that makes immobilization of antibodies simple. In this application note, OpenSPR™ is used demonstrate the use of the Protein A kit by analyzing the KD of the interaction between Ubiquitin and Anti-Ubiquitin Antibody.