Aggregation of rhDNase Occurred During the Compression of KBr Pellets Used for FTIR Spectroscopy |
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Authors: | Chan Hak-Kim Ongpipattanakul Boonsri Au-Yeung Jacky |
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Affiliation: | (1) Department of Pharmaceutical Research and Development, Genentech, Inc., 460 Point San Bruno Boulevard, South San Francisco, California, 94080;(2) Present address: Department of Pharmacy, University of Sydney, NWS 2006, Australia |
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Abstract: | Purpose. To determine if a protein changes when it is compressed into a KBr pellet for FTIR spectroscopy measurement in the solid state, using recombinant human deoxyribonuclease I (rhDNase) as an example.Methods. Lyophilized rhDNase with KBr compressed at different pressures were analyzed by FTIR spectroscopy, size exclusion HPLC and enzymatic activity assay. Different protein/KBr weight ratios and residual water contents were studied for their possible effects on aggregation.Results. Depending on the pressure, a loss of enzymatic activity accompanied by an increase in soluble high molecular weight aggregates of the protein (up to ~15%) was demonstrated. Aggregation was reduced to less than 5% by a suitable dilution of the protein in KBr (1 in 1000). In contrast, water content variability (1–11 wt. %) did not affect aggregation.Conclusions. The findings emphasize the importance to examine for protein integrity when using the KBr method for FTIR sample preparation. Protein aggregation may be minimized by optimizing the sample preparation condition such as changing the protein/KBr weight ratio. |
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Keywords: | rhDNase FTIR spectroscopy compression protein aggregation KBr pellets |
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