Infrared spectroscopy for biopharmaceutical protein analysis

A mid-infrared transmission spectroscopic method with the possibility of high sample throughput was developed and validated on the basis of GMP requirements for protein therapeutics. In comparison with the method predominantly used, i.e. the surface-sensitive attenuated total reflection (ATR), we have shown that transmission measurements in solution possess several advantages, such as quantitative analysis on the basis of Lambert–Beer's law, determination of identity and purity based on specifically developed identity criteria, characterization of protein structure and structural changes including aggregation in solution and study of ligand binding to the protein. The usefulness of this method is exemplified by the characterization of the drug substance of ONCOHIST® (recombinant human histone H1.3 and bis-Met-histone H1.3) and its interaction with phosphate ions. Our conclusion is that transmission mid-infrared spectroscopy is a powerful tool for protein analysis in biotechnology and supplements the current analytical techniques for biopharmaceutical quality control of therapeutic proteins.