A diffusion NMR method for the prediction of the weight-average molecular weight of globular proteins in aqueous media of different viscosities
We have introduced for the first time, a non-viscosity dependent universal calibration curve (UCC) for the successful prediction of the weight-average molecular weights of globular proteins in the range of 8.5–66.2 kDa with no dependence on the solvent viscosity. Plots of log(Dη) versus log Mw showed excellent linearity (R2 > 0.99) within four different methods (LMS, TRAIn, NNLS and ITAMeD). To demonstrate the applicability of this new UCC curve, we have proposed as a proof of concept the determination of the Mw of myoglobin from an equine heart in deuterated water of four different viscosity values. The corresponding (Dη) values were fitted to the UCC to calculate their corresponding weight-average Mw that was in all the cases centered at 17 321.2 Da, with differences in the mass below 5.7% with respect to the commercial value.