An analytical perspective of NMR spectroscopy of biological fluids and cells

Dimethylsulfoxide oxidizes glutathione in vitro and in human erythrocytes: Kinetic analysis by 1H NMR

The interaction of dimethylsulfoxide (Me2SO) with glutathione was investigated under non-equilibrium conditions in solution using 1H NMR and in intact erythrocytes using 1H spin-echo NMR. In solution the reaction was observed to follow second-order kinetics (Rate = k1[glutathione][Me2SO]) at 300 K pH 7.4, k(sol) = 4.7 x 10(-5)mol(-1)L(1)s(-1). In intact erythrocytes the rate constant for the cellular environment, k(cell), was found to be slightly larger at 8.1 x 10(-5)mol(-1)L(1)s(-1). Furthermore, the reaction of Me2SO with erythrocyte glutathione showed a biphasic dependence on the Me2SO concentration, with little oxidation of glutathione occurring until the Me2SO concentration exceeded 0.5 molL(-1). The results suggest that at lower concentrations, Me2SO can be effectively removed, most probably by reaction with glutathione, which is regenerated by glutathione reductase, although preferential reaction with other cellular components (e.g., membrane or cellular thiols) cannot be ruled out. Thus the concentrations of Me2SO that are commonly used in cryopreservation of mammalian cells ( approximately 1.4 molL(-1)) can cause oxidation of intracellular glutathione.

Proton nuclear magnetic resonance spectroscopy of urine for rapid multicomponent analysis of intraoperative cellular metabolites

We serially measured the proton nuclear magnetic resonance spectra of the urine of intraoperative patients over time to assess their potential use for rapid multicomponent analysis of cellular metabolites. Within a few minutes, the spectra provided signals of many low molecular weight urinary metabolites, including amino acids, ketone bodies, lactate, and glucose. The proton magnetic resonance spectra of the urine of most of the intraoperative patients showed large increases in urinary excretion of alanine, ketone bodies, and lactate and/or glucose, confirming alterations in energy substrate-endocrine relationships during the perioperative period. These metabolic changes appeared to be roughly proportional to the degree of surgical stress, but they were not consistent among patients who underwent the same operation. The study suggests that routine intraoperative metabolic monitoring is necessary to prevent critical metabolic disorders and that proton nuclear magnetic resonance spectroscopy of urine may meet this need by allowing rapid multicomponent analysis of cellular metabolites.

Laboratory support for the poisoned patient

Poisoning often does not require toxicology laboratory analysis, though support is necessary from the departments of hematology and biochemistry. There are some compounds, such as paracetamol (acetaminophen), lithium, and methanol, for which quantitative or qualitative analysis is essential for effective patient management. Standard methods such as immunoassays, chromatography, and spectrophotometry have been extended by mass spectrometry and will be enhanced by nuclear magnetic resonance and by hyphenated techniques (e.g., LC-MS-MS). The new perspectives that can be gained with these techniques may greatly improve our knowledge of toxicokinetics and enable better patient management. Comatose patients and those with suspected brain death comprise a difficult group requiring comprehensive toxicologic screens. Although current immunoassay-chromatography methods are adequate, it is to be hoped that more comprehensive screens are achievable. The author has performed trials on TLC-FABMS-MS as a potential procedure and has obtained satisfactory preliminary results. This and other spectrometric-spectroscopic methods may be the techniques of the future for reference centers.