Infrared spectroscopic studies of protein formulations containing glycine

Infrared spectroscopic studies of protein formulations containing glycine
March 2004
Jeffrey D. Meyer 1, Shu Jun Bai 1, Meena Rani 2, Raj Suryanarayanan 2, Rajiv Nayar 3, John F. Carpenter 1, Mark C. Manning 1
1Center for Pharmaceutical Biotechnology, University of Colorado Health Sciences Center, Denver, Colorado
2College of Pharmacy, University of Minnesota, Minneapolis, Minnesota
3HTD Biosystems, Hercules, California
Journal of Pharmaceutical Sciences, Volume 93, Issue 5 , Pages 1359 - 1366
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Abstract
Glycine is extensively used as an excipient in protein formulations. However, it absorbs significant infrared (IR) radiation in the conformationally sensitive amide I region (1700-1600 cm-1) of proteins. Furthermore, glycine can form a number of polymorphs, as well as an amorphous phase. Each of these forms possibly exhibits a different IR absorption spectrum. Accurate subtraction of glycine signals, in order to obtain reliable amide I spectra, was found to be possible only if the protein-to-glycine ratio was 1:1. In those cases, the solid-state conformation of the protein could be determined. In addition, a new method for estimating the degree of crystallinity of freeze-dried glycine is described, using IR bands in the 1350-1300 cm-1 region. ? 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1359-1366, 2004
Keywords
lyophilization ? crystallinity ? infrared spectroscopy ? protein formulation ? X-ray diffraction ? glycine