12 BioPharm International
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Emerging Therapies eBook September 2024 www.biopharminternational.com
Cell
Line
Development
FIGURE 3. The National Institute of Standards and Technology monoclonal antibody
(NISTmAb) intact charge profiles showing: A) an imaged capillary isoelectric focusing
ultraviolet (icIEF–UV) profile of charge variant separation in the scale of the isoelectric
point (pI) value (x-axis); B) a mass spectrometry (MS) base peak electropherogram
(BPE) of mAb charge variants acquired after icIEF separation; and C) an overlay of the
intensity-normalized deconvoluted intact mass spectrum of the five NISTmAb charge
variants showing the identity of the peaks detected in the icIEF–UV/MS analysis via
a software program (Biologics Explorer, SCIEX). Normally the deconvoluted mass
(detected intact mass) does not have 1 Da resolution, and the 1 Da shift may be
artifacts. In this case, however, due to the icIEF separation, the 1 Da mass shifts could
be real and related to different deamidation modification levels (6,11,12).
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