However, a comprehensive evaluation of protein precipitation and ultrafiltration approaches with regard to the absolute quantitation of metabolites using NMR is currently lacking.
In this study, we have comprehensively evaluated the performance of protein precipitation and ultrafiltration approaches using 1D and 2D NMR, based on exhaustive identification and absolute quantitation of human blood metabolites.
In this study, we have comprehensively evaluated the performance of protein precipitation using methanol, acetonitrile, perchloric acid, and trichloroacetic acid and ultrafiltration approaches using 1D and 2D NMR, based on the identification and absolute quantitation of 44 human blood metabolites, including a few identified for the first time in the NMR spectra of human serum.
This apparent molecular mass range is in accordance with the ultrafiltration membrane approach.
The other approach, ultrafiltration, which has also been investigated for MS applications in detail, shows a significant loss of hydrophobic metabolites due to the strong protein binding or adsorption to the membrane.
While a similar amount of weight loss was achieved with the two approaches, ultrafiltration was associated with a higher rate of adverse events [ 76].
Several guidelines state that ultrafiltration is another reasonable approach for patients with refractory congestion not responding to diuretic therapy [ 69, 70].
In the first such synthesis, Bayer and Mutter bound peptides to mono-methyl PEG-10 000 (mPEG) that was purified by ultrafiltration.[ 24] This approach was repeated for oligos by the same laboratory, using the now obsolete phosphodiester coupling strategy and either PVA or PEG-10 000 polymeric supports.[ 17] However, there was no further development of this approach for either biopolymer.
Higher titers can be achieved by physical concentration [ 2], including ultracentrifugation [ 3, 9- 11], or filtration approaches such as ultrafiltration [ 3, 10, 12- 14], and diafiltration [ 4, 6].
The first approach is mainly used in ultrafiltration processes.
