A diffusion NMR method for the prediction of the weight-average molecular weight of globular proteins in aqueous media of different viscosities

Abstract

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 M_w 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 M_w 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 M_w 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.