CALCULATION OF THE MOLECULAR-WEIGHT OF PROTEINS FROM ELECTROPHORETIC AND GEL EXCLUSION CHROMATOGRAPHIC EXPERIMENTS

The molecular weights of proteins or protein subunits are frequently e stimated from the electrophoretic mobility in the presence of sodium d odecyl sulphate, or from the elution volume in gel filtration chromato graphy. Using a series of standards of known size, a calibration curve is prepared which often yields a straight line in a semilogarithmic p lot; interpolation from this line then gives the size of the sample. W hile this method is simple to apply, it does not give any estimate of the accuracy of the determined size. Furthermore there is no objective criterion for deciding if the calibration curve is linear, or a proce dure for dealing with non-linear calibration curves. Here I report a m ethod and a computer program which uses appropriate statistical method s to select the best straight or curved calibration line. The size of the unknown is then interpolated and an estimate or the error in this value is calculated.