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Handbook of Size Exclusion Chromatography and Related ...

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detection has gained increasing popularity among protein chromatographers<br />

during the past decade (72–76).<br />

AMALS detector together with aconcentration detector, typically UVor<br />

differential refractive index (DRI) detector, measures the molar mass <strong>of</strong> protein<br />

independent <strong>of</strong> the shape <strong>of</strong> the protein or the elution volume in SEC as<br />

demonstratedbyFigs3<strong>and</strong>4.InFig.4,theelution<strong>of</strong>proteinXismuchlaterthan<br />

expected from its actual molecular weight, therefore prediction <strong>of</strong> the molecular<br />

weight <strong>of</strong> protein X from SEC elution volume alone would provide an erroneously<br />

low molecular weight. The theory <strong>and</strong> applications <strong>of</strong> MALS detection for<br />

polymer characterization are summarized elsewhere in this book.<br />

More recently, therapeutic proteins are <strong>of</strong>ten modified with polymers, such<br />

as polysaccharides <strong>and</strong> polyethylene glycol, to reduce immunogenicity <strong>and</strong> the<br />

clearance rate from the body as well as to improve drug efficacy (77). The<br />

Figure 3 Chromatograms from native <strong>and</strong> reduced carboxymethylated RNase. Reduced<br />

RNA is unfolded with a more extended structure <strong>and</strong> thus eluted much earlier. Column<br />

calibration estimated a molecular weight <strong>of</strong> 41kD. The combination <strong>of</strong> light-scattering <strong>and</strong><br />

refractive index detectors determines the molecular weight <strong>of</strong> both reduced <strong>and</strong> native<br />

RNAse to be 13.7kD, as theory suggests. (From Ref. 2.)<br />

© 2004 by Marcel Dekker, Inc.

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