On the basis of the calibration of a Sephadex G-200 column with protein standards of known molecular weights, you estimate the apparent molecular weight of a new protein you have isolated from Drosophila mutants revealing accelerated neurodegeneration to be 68 kDa (or 68,000 g/mol). However, when you subject the same protein to SDS-PAGE, the size you estimate using gel electrophoretic calibration standards is only 17 kDa (or 17,000 g/mol). Since you are concerned by this discrepancy, you decide to estimate the molecular weight of this protein by the sedimentation velocity method. In so doing, you determine that the protein has a diffusion coefficient of 1.5 x 10-7 cm2/sec and a sedimentation coefficient of 1.09627 x 10-13 sec at 20oC (293 K). The density of the buffer solution you use for the sedimentation measurement is 0.998 g/cm3at 20oC.
Assuming the partial specific volume is 0.74 cm3/g for this protein, which of the two measurements (size-exclusion chromatography or SDS-PAGE) provides the most accurate estimate of the native molecular weight of the protein?
