(408d) Aggregation of Proteins Studied by Deep UV Resonance and Nonresonance Raman Spectroscopy

Aggregation of proteins is one of the degradation processes which occurs during the storage of pharmaceutical protein products, and can significantly decrease the potency of protein drugs.  Several studies have shown that aggregation correlates with changes in the secondary structure of proteins.  Raman spectroscopy is a nondestructive analytical method that is sensitive to the secondary structure of proteins.  Deep UV resonance Raman (DUVRR) spectroscopy has the potential to be a good alternative technique to UV and vibrational circular dichroism for determination of secondary structure in formulated therapeutic proteins.  The resonance excitation increases the Raman signal, specifically enhancing the intensity of peptide vibration bands, and completely removing fluorescence background.  The advantage of DUVRR spectroscopy is that it does not usually require any sample preparation and is as sensitive as circular dichroism.  We have developed a mathematical algorithm for mixture decomposition in order to remove excipient spectral contributions from the total Raman signal of formulated protein products.  This presentation will discuss the use of DUVRR spectroscopy to study the aggregation of insulin and insulin variants, and will compare the capabilities of resonance Raman and nonresonance Raman spectroscopies.