Abstract: Maintenance of acidbase homeostasis is vital for living organism. Changes of H+ concentration (pH) in blood serum may result in adverse physiological consequences. In this study, the effects of pH changes on human blood serum were studied by T₂-weighted and diffusion-weighted ¹H NMR spectroscopy and saturation transferred difference (STD) experiments. The chemical shifts and concentrations of the metabolites in the serum were measured in serum samples with pH varied between 7.0 and 7.8. It was demonstrated that, from pH 7.0 to pH 7.8, the chemical shifts of many low molecular-weight metabolites drifted upfield and the intensities of phenylalanine, tyrosine, histidine, and lactate in the T₂-weighted NMR spectra changed significantly. No significant changes in the protein signals were observed, except that the signal from albumin lysyl shifted towards upfield.

Key words: NMR, human serum, metabolite, pH