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Calcium-Binding Protein Protocols Calcium-Binding Protein Protocols

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MALLS and Sedimentation Equilibrium 129<br />

Fig. 1. Overlay of the 90° laser light scattering (———) and the DRI (- - - - -)<br />

chromatograms for E-cadherin in the absence of calcium. A 30-µL aliquot of a 7 mg/mL<br />

solution was injected at a flow rate of 0.8 mL/min. E-cadherin eluted as a single, narrow,<br />

symmetrical peak with a calculated weight average molecular weight of 24,370.<br />

The peak that appears at the void volume on the 90° chromatogram and is absent on<br />

the DRI chromatogram results from a pressure effect from the sample injection (see<br />

Subheading 2.5., item 3).<br />

scale signal in the Optilab 903). Data is collected until the peaks of interest have<br />

eluted and the MALLS and DRI signals have returned to baseline levels.<br />

2.4. Data Analysis<br />

1. Data is analyzed using Wyatt Technology’s Astra and Easi software following<br />

procedures outlined in the Dawn F instrument manual (1) and by Wyatt (3). The<br />

peak in the E-cadherin chromatogram (see Fig. 1) consists of many data slices<br />

collected in both the Dawn F and Optilab 903. Using either a measured or estimated<br />

value for the specific refractive increment, dn/dc (i.e., 0.185 for BSA), the<br />

concentration of each MALLS data slice is determined from the intensity of the<br />

corresponding Optilab data slice.<br />

2. Combining this concentration value with the measured scattering intensities at<br />

the various angles in the Dawn F, a Debye plot (R Θ/K*c vs sin 2 Θ/2), where K* is

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