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Joyce Johnson

Application Note: Comparing pH and Buffer Solutions for Stabilizing a Monoclonal Antibody using the SUPR-CM High-Performance Plate Reader

The stability of a monoclonal antibody is quantified for different buffer solutions including MOPS, TRIS, sodium phosphate and sodium citrate. The impact of pH on the stability of the antibody was assessed for each buffer solution using chemical denaturation, and fluorescence spectra measured with the SUPR-CM plate reader. For each buffer solution, the better performing pH values where selected for further analysis where they were compared with each other to determine which buffer solution increased the stability of the antibody the most. Quantification of the antibody’s stability was achieved via fitting of a three-state function to the ratio of intensities (355 nm and 330 nm). The Gibbs Free Energies and mid-point of inflections where compared for each buffer solution as the means to assess the changes in antibody stability. Both MOPS and TRIS buffers increased the mid-point of inflection values over phosphate and citrate buffers which made them more favorable buffer solutions for this antibody. Between MOPS and TRIS, the TRIS buffer had the larger mid-point of inflection value, for the second transition region. However, The MOPS buffer sample had larger Gibbs Free Energy values and mid-point of inflection value for the first transition region which made it the more favorable buffer solution for this monoclonal antibody.

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