Molecular weights of subunit components of bovine casein micelles

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Abstract
Summary: Using either Sephacryl S-300 or TSK-G4000SW gel chromatography, the larger of the two major components of bovine casein micelles (F2) was eluted at the same retention time irrespective of sample concentration and column temperature. Its mol. wt was estimated to be 500K by examination of the eluate from a TSK-gel G4000SW column using a low-angle laser light-scattering photometer and a precision differential refractometer. With the second component (F3), retention time in Sephacryl gel chromatography was significantly affected by both sample concentra-tion and volume applied. Limiting retention times for F3 could be obtained by extrapolation of these two parameters to higher and lower values, and corresponded to those of water-soluble protein with mol. wt 200K and 100K respectively. Approach to sedimentation equilibrium technique at the above limiting sample concentrations gave values of F3 consistent with the above molecular weight. Sephacryl gel chromatography at either low sample concentration or low column temperature resulted in a new component being eluted at a position of mol. wt 25K