Figure 2:

Comparison of a portion of ¹H NMR spectra of the same pooled human serum sample obtained by suppressing protein signals by (a) T₂ filtering using the CPMG pulse sequence; (b) ultrafiltration using a 3 kDa molecular weight cut-off filter; and (c) protein precipitation using methanol (1:2 v/v). In (a) most of the metabolite signals are missing or significantly attenuated, while in (b) many metabolites including tryptophan, benzoate and formate are significantly attenuated when compared to (c) (Reproduced with permission from Nagana Gowda et al. 2014b).