Kimberly Osborn, “Developing and Testing a Labeling Reagent for Human IgG Antibodies”
Mentors: Ionel Popa and Annie Eis, Physics

Antibodies show potential to be used in a variety of applications, but they are difficult to work with due to natural variation. Tagging them in a consistent location and orientation is not easy. If a tag is placed wrong, issues can arise such as antibody deactivation, interrupted delivery of drugs, or loss of the ability to track the antibody. Tagging via secondary labeling currently exists in several forms such as proteins A, G and L, but there is a need to engineer new protein forms to ameliorate tagging issues. To tackle this goal and facilitate the rise of antibody technology, we engineered variants of protein L attached to the fluorescent protein meGFP. Protein L is secreted by the bacterium Peptostreptococcus magnus. It has the special property of binding to the kappa light chain region of antibodies without interfering with their functions. Here, we demonstrate a new method of measuring the binding of our engineered protein L to the kappa light chain region of antibodies. This method relies on using the fluorescent signal from the GFP domain of our protein L to measure its binding affinity (Kd) to antibodies. This is tested using gel electrophoresis. This method has the advantage of being simple to use and can measure binding constants in the nanomolar to micromolar range.