Microwave enhanced synthesis of halogenated derivatives of L-tyrosine labeled with deuterium in aromatic ring

Three halogenated derivatives of L-tyrosine, selectively labeled with deuterium in aromatic ring, i.e., 3′-fluoro-[5′-2H]-, 3′-chloro-[5′-2H]-, and 3′-iodo-[2′,5′-2H2]-L-tyrosine, were synthesized using microwave assisted acid-catalyzed isotope exchange between 3′-fluoro-, 3′-chloro- and 3′-iodo-L-tyrosine and heavy water. The degree of deuterium incorporation was confirmed by 1H NMR spectroscopy. The spectroscopic data indicate that isotope exchange depends on the method of heating and the power of microwaves. The deuterium enrichment of 3′-fluoro-[5′-2H]- and 3′-chloro-[5′-2H]-L-tyrosine amounted to 70% and 60%, respectively, while for 3′-iodo-[2′,5′-2H2]-L-tyrosine this value was about 50% and 95% for the 2′- and 5′-position. The isotopomers were obtained in good chemical yields of 50–70%.

Slight Deuterium Enrichment in Water Acts as an Antioxidant: Is Deuterium a Cell Growth Regulator?

Small admixtures in water, e.g. of metal ions, often act as cell growth regulators. Here we report that enrichment of deuterium content in water, normally found at 8 mm concentration, two-three folds increases cell proliferation and lowers the oxidative stress level as well. Acting as an anti-oxidant, deuterium-enriched water prevents the toxic effect of such oxidative agents as hydrogen peroxide and auranofin. This action is opposite to that of deuterium depletion that is known to suppress cell growth and induce oxidative stress in mitochondria. We thus hypothesize that deuterium may be a natural cell growth regulator that controls mitochondrial oxidation-reduction balance. Because growth acceleration is reduced approximately by half by addition to water a minute amount (0.15%) of 18O isotope, at least part of the deuterium effect on cell growth can be explained by the isotopic resonance phenomenon. A slight (≈2-fold) enrichment of deuterium in water accelerates human cell growth. Quantitative MS based proteomics determined changes in protein abundances and redox states and found that deuterium-enriched water acts mainly through decreasing ROS production in mitochondria. This action is opposite to that of deuterium depletion that suppresses cell growth by inducing oxidative stress. Thus deuterium may be a natural cell growth regulator that controls mitochondrial oxidation-reduction balance. The role of isotopic resonance in this effect was validated by further experiments on bacteria.

Plant water resource partitioning and xylem-to-leaf deuterium enrichment in Lanzhou, northwest China

Lanzhou lies at the western Loess Plateau, China, and has a typical semi-arid temperate continental climate. Plants in this area are exposed to a prolonged dry season. In this study, we measured the stable isotopes of hydrogen (δD) and oxygen (δ18O) of the local precipitation, river water, soil water, plant xylem water, and leaf water at four sampling sites during the 2016 growing season. Our results showed that plants relied mostly on wet season precipitation at sites N1, N2, and N3 because this recharged the soil after the long dry season. Leaf phenology had a significant effect on evaporation distance (ED) value, and evergreen plants have adapted to water tapping from deep soil water sources during the dry season. The ED values of trees and shrubs were quite different in the dry season, indicating water competition among different plant species was mitigated due to water resource partitioning. Moreover, plants at site N4 relied on a water source admixed with river water throughout the whole growing season. The mean value of xylem-to-leaf water deuterium enrichment (ɛl/x) was −0.91 ± 0.36‰ over all plant species, seasons, and sampling sites. Plant species, leaf phenology, and seasons were found to be the primary factors influencing the ɛl/x, while growth form and elevation had negligible effects.

Hydrogen isotopic evidence for early oxidation of silicate Earth

The Moon-forming giant impact extensively melts and partially vaporizes the silicate Earth and delivers a substantial mass of metal to Earth's core. Subsequent evolution of the magma ocean and overlying atmosphere has been described by theoretical models but observable constraints on this epoch have proved elusive. Here, we report calculations of the primordial atmosphere during the magma ocean and water ocean epochs and forge new links with observations to gain insight into the behavior of volatiles on the early Earth. As Earth's magma ocean crystallizes, it outgasses the bulk of the volatiles into the primordial atmosphere. The redox state of the magma ocean controls both the chemical composition of the outgassed volatiles and the hydrogen isotopic composition of water oceans that remain after hydrogen loss from the primordial atmosphere. Whereas water condenses and is retained, molecular hydrogen does not condense and can escape, allowing large quantities (~10^2 bars) of hydrogen - if present - to be lost from Earth in this epoch. Because the escaping inventory of H can be comparable to the hydrogen inventory in the early oceans, the corresponding deuterium enrichment can be large with a magnitude that depends on the initial H2 inventory. By contrast, the common view that terrestrial water has a carbonaceous chondrite source requires the oceans to preserve the isotopic composition of that source, undergoing minimal D-enrichment via H2 loss. Such minimal enrichment places upper limits on the amount of primordial H2 in contact with early water oceans (pH2<20 bars), implies oxidizing conditions for outgassing from the magma ocean, and suggests that Earth's mantle supplied the oxidant for the chemical resorption of metals during late accretion.

Validation of data provided by the deuterium oxide dose-to-mother technique for better evaluation of breastfeeding practice

We describe a simple method to validate data collected from a study using the deuterium oxide dose-to-the-mother technique for breastfeeding evaluation. We used human milk intake calculation spreadsheets (n=180). The calculation was performed by fitting the deuterium enrichment data to a model for water turnover in the mother and in the baby. We assumed that the validity of the results is as high as the square root mean square error (SRMSE) between calculated and fitted data is low. Based on the original spreadsheets that fitted well with the model (n=87), we developed a simple prediction of the SRMSE and we used it as cut-off to check, correct (by removing enrichment data) and validate or remove the other spreadsheets. We found a cut-off dependent on the measured enrichment (E_m) that was And the mean SRMSE (90%CI) of the fitted sheets was 23.37 mg.kg-1 (22.01 mg.kg-1, 24.73 mg.kg-1) with a maximum of 38.96 mg.kg-1. After correction we noticed that the number of enrichments removed per file varied from 1 to 4. We observed within the corrected spreadsheets a significant reduction (p≤0.0001, n=53) of the SRMSE (90%CI) from 49.78 mg.kg-1 (46.35 mg.kg-1, 53.20mg.kg-1) before correction to 25.88 mg.kg-1 (24.13 mg.kg-1, 27.64 mg.kg-1) after correction. We also observed that after correction, the mean difference (90%CI) of HM respectively non-HM that was 29.34 mg.kg-1 (21.71 mg.kg-1, 36.97 mg.kg-1) respectively 24.13 mg.kg-1 (17.4 mg.kg-1, 30.79 mg.kg-1) was strongly (p≤0.0001, n=53) different from zero. Therefore, the correction is very important to optimizing the results. Keywords: Breastfeeding; Deuterium; Excel spreadsheet; Square root mean square error; Validation