Protein size on SDS gel - (Sep/18/2008 )

Does anyone know if protein usually appear to have a higher or lower molecular weight
than its theorectical size when ran on gel. Thanks

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this question cannot be answered in general as various PTM modify size of a polypeptide; however, what can be said in principle, the preciseness of molecular mass in SDS-PAGE has a variation of +/- 10% which depends on the method. So you have to perform multiple runs, and mass determinations (Neville plots) to find a mass...

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