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Traditionally, nuclear spin is not considered to affect biological processes. Recently, this has changed as isotopic fractionation that deviates from classical mass dependence was reported both in vitro and in vivo. In these cases, the isotopic effect correlates with the nuclear magnetic spin. Here, we show nuclear spin effects using stable oxygen isotopes ( 16 O, 17 O, and 18 O) in two separate setups: an artificial dioxygen production system and biological aquaporin channels in cells. We observe that oxygen dynamics in chiral environments (in particular its transport) depend on nuclear spin, suggesting future applications for controlled isotope separation to be used, for instance, in NMR. To demonstrate the mechanism behind our findings, we formulate theoretical models based on a nuclear-spin-enhanced switch between electronic spin states. Accounting for the role of nuclear spin in biology can provide insights into the role of quantum effects in living systems and help inspire the development of future biotechnology solutions.

Rationale: Measurements of oxygen-17 excess ((17)Oexcess) in carbonates have become of great importance. However, to compare results obtained by different laboratories, it is necessary to normalize them to international standards. With this purpose in mind, we measured accurate and high precision δ(17)O and (17)Oexcess values for NBS19 and NBS18, two international standards, for which δ(18)O values are already widely used as the references for carbonates., Methods: The measurements are based on isotopic exchange at steady state between O2 and CO2 over hot platinum sponge at 750°C. Dual-inlet isotope ratio mass spectrometry (IRMS) measurements of the δ(17)O and δ(18)O values of this O2 allow δ(17)O values of CO2 to be obtained with very high precision (0.01 to 0.03‰) and, correspondingly, accurate (17)Oexcess values with a precision of 5 per meg., Results: We measured, for the first time, the δ(17)O values and (17)Oexcess of CO2 liberated from NBS19 at 25°C (39.196 ± 0.026; 20.276 ± 0.015‰ and -227 ± 4 per meg, respectively) and NBS18 (17.591 ± 0.041‰; 9.253 ± 0.018‰ and 3 ± 5 per meg, respectively). The values are given versus VSMOW., Conclusions: Accurate values of δ(17)O and (17)Oexcess of the international standards NBS19-CO2 and NBS18-CO2 are now available. The new values should be used for normalization of measured oxygen isotope ratios of carbonates to allow meaningful comparison of results among different laboratories., (Copyright © 2015 John Wiley & Sons, Ltd.)

A method for high-precision and high-accuracy mass spectrometric measurements of the ratios among the three oxygen isotopes, and of the O(2)/Ar ratio, is presented. It involves separation of the O(2)-Ar mixture from air and includes a fully automated system that ensures highly reliable sample processing. Repeated measurements of atmospheric oxygen yield the repeatability (+/-SE x t, standard error of the mean (n = 12) multiplied by Student's t-factor for a 95% confidence limit) of 0.004, 0.003 and 0.2 per thousand for delta(18)O, delta(17)O and delta O(2)/Ar, respectively., (Copyright 2003 John Wiley & Sons, Ltd.)

The 18O content of atmospheric O2 is an important tracer for past changes in the biosphere. Its quantitative use depends on knowledge of the discrimination against 18O associated with the various O2 consumption processes. Here we evaluated, for the first time, the in situ 18O discrimination associated with soil respiration in natural ecosystems. The discrimination was estimated from the measured [O2] and δ18O of O2 in the soil-air. The discriminations that were found are 10.1 ± 1.5‰, 17.8 ± 1.0‰, and 22.5 ± 3.6‰, for tropical, temperate, and boreal forests, respectively, 17.9 ± 2.5‰ for Mediterranean woodland, and 15.4 ± 1.6‰ for tropical shrub land. Current understanding of the isotopic composition of atmospheric O2 is based on the assumption that the magnitude of the fractionation in soil respiration is identical to that of dark respiration through the cytochrome pathway alone (∼18‰). The discrimination we found in the tropical sites is significantly lower, and is explained by slow diffusion in soil aggregates and root tissues that limits the O2 concentration in the consumption sites. The high discrimination in the boreal sites may be the result of high engagement of the alternative oxidase pathway (AOX), which has high discrimination associated with it (∼27‰). The intermediate discrimination (∼18‰) in the temperate and Mediterranean sites can be explained by the opposing effects of AOX and diffusion limitation that cancel out. Since soil respiration is a major component of the global oxygen uptake, the contribution of large variations in the discrimination, observed here, to the global Dole Effect should be considered in global scale studies.

A time series of the 17O-excess (17Δ) was measured in the Gulf of Elat (Aqaba) between May 2007 and August 2009. While 17Δ is expected to behave conservatively below the photic zone, we observed a ? increase of 20 per meg in the water residing below 300 m along a period of 3 months, which was followed by a 17Δ decrease of 60 per meg, which occurred over 7 months. The 17Δ increase and decrease indicate penetration of photosynthetic O2, followed by penetration of atmospheric O2 into the deep water. In order to test whether vertical mixing could explain the observed variations in 17Δ, we compared our results with simulated values obtained from a one dimensional hydrodynamic model, which was extended to include dissolved O2 isotopes. Our model simulations successfully reproduced the observed temperatures, salinities and dissolved O2 concentrations in the gulf. In addition, the evaporation rate estimated by the model (1.7 m x year-1) and the advective heat flux from the Red Sea (110 W x m-2 over 3 months) were in good agreement with previous studies. However, the model could not reproduce the observed variations in 17Δ in the deep water, regardless of the gross O2 production and the air-sea gas exchange rates used. This discrepancy shows that horizontal mixing processes have an important role in the interaction between deep and surface water in the gulf. We suggest that for the most part, these processes occur along the boundaries of the gulf. [ABSTRACT FROM AUTHOR]

[i] Atmospheric O2 is almost 24%o more enriched in 18O than seawater, and this enrichment is known as the Dole effect. For a long time it has been accepted that there is no oxygen isotope fractionation in photosynthesis, and thus the Dole effect should be the result of preferential terrestrial and marine respiratory consumption of 16O over 18O, and also several permil enrichment of leaf water from which terrestrial photosynthesis produces 18O enriched O2. This concept has led to the understanding that the record of past Dole effect variations was strongly affected by changes in the ratio of photosynthetic production between land and sea. However, recent studies in our lab have led to two major new observations: (1) O2 produced by certain marine phytoplankton, representing important groups of primary producers, is significantly enriched (up to 6%o) in 18O with respect to the substrate seawater and (2) effective oxygen isotope fractionation in soil respiration is considerably smaller than the intrinsic respiratory fractionation. Here we take these two observations into account and show that the magnitudes of the terrestrial and marine components of the Dole effect are close, and both are close to the measured Dole effect. As a result, the magnitude of the global Dole effect should not be sensitive to past changes in the ratio of land-to-sea photosynthetic rates. Instead of the land-sea control, variations in low-latitude hydrology, and possibly changes of fractionations in the marine biosphere, are more important in regulating the magnitude of the Dole effect and its past variations. [ABSTRACT FROM AUTHOR]

Abstract: Recently, a new method has been introduced for the estimation of photosynthetic oxygen production from the triple isotope composition (δ17O and δ18O) of dissolved O2 in the ocean and of air O2 in ice cores. This method is based on the deviations (17Δ) from mass dependent respiratory fractionation, the major process affecting the isotopic composition of air O2. To apply this method, the slope in the 17O/16O vs. 18O/16O relationship used for 17Δ calculation must be known with high accuracy. Using numerical simulations and closed system experiments, we show how the respiratory slope is manifested in the 17Δ of O2 in situations where respiration is the only process affecting oxygen isotopic composition (kinetic slope), and in systems in steady state between photosynthesis and respiration (steady state slope). The slopes of the fractionation line in these two cases are different, and the reasons of this phenomenon are discussed. To determine the kinetic respiratory slope for the dominant O2 consumers in aquatic systems, we have conducted new experiments using a wide range of organisms and conditions and obtained one universal value (0.5179 ± 0.0006) in ln(δ17O + 1) vs. ln(δ18O + 1) plots. It was also shown that the respiratory fractionations under light and dark are identical within experimental error. We discuss various marine situations and conclude that the kinetic slope 0.518 should be used for calculating 17Δ of dissolved O2. In contrast, a steady state fractionation slope should be used in global mass balance calculations of triple isotope ratios of O2 in air records of ice cores. [Copyright &y& Elsevier]

Looks at triple-isotope composition of atmospheric oxygen as a tracer of biosphere productivity. The three natural occurring isotopes of oxygen; Dependence on the isotopic composition of photosynthetically produced O2 from terrestrial and aquatic plants; Estimate of the size of the 17O/16O anomaly in tropospheric O2; Reflection of the influence of the influence of biospheric cycling and stratospheric photochemical processes; Proposal.

By use of in situ bottle incubations, we determined three variables for the characterization of plankton community primary productivity in Lake Kinneret, Israel: (1) H218O-based primary productivity (18OP), measured by 34O2 (18O16O) evolution; (2) radiocarbon-uptake-based primary productivity (14CP); and (3) net O2 production (NOP), calculated from the rate of O2 : Ar change. Six experiments were conducted in the fall, a period that is characterized by thermocline deepening, erosion of the hypolimnion, and eventual introduction of high concentration of reduced substances into the epilimnion. An additional experiment was conducted in spring. In comparison to net O2 evolution, the tracer-based methods severely underestimated primary productivity in the fall. This is indicated by unusually high NOP: 18OP and NOP: 14CP ratios (1-2.2 and 2-4, respectively). The latter is considerably different than the typical values of aquatic environments (∼1.4). In contrast to these ratios, the 18OP: 14CP appears normal (1.6-2.9) and not significantly different from previous results in the lake. Ammonium was the major nitrogen source in the fall experiments, and there is no reason to assume that the cellular composition of phytoplankton was exceptional. It is therefore unlikely that the high NOP: 14CP ratio represents genuine ratios of oxygen and carbon metabolism. We suggest that an explanation accounting for the high values of both NOP: 18O P and NOP: 14CP can be slow diffusion of the tracers in and out of phytoplankton cells. [ABSTRACT FROM AUTHOR]

During the electrolysis of water in an acidified medium, ozone is produced, in association with oxygen, at the anode. This ozone is found to be depleted in heavy isotopes (18O and 17O), with respect to the source water, following a strict mass-dependent rule. Our experiments also suggest that the isotopes are distributed at the apex and base positions of the bent ozone molecule in a random fashion, without obeying the zero-point energy constraint. Endowed with these characteristics, the electrolytic ozone provides a source of reference that has a known internal heavy isotope distribution for spectroscopic studies. In addition, this ozone, when subjected to photolytic decomposition, can be used as a source of atomic oxygen with mass- dependent isotope ratios that can be varied by simply changing the water composition. Such an oxygen source is important for studying isotope effects in gas-phase recombination/exchange reactions such as COO + O* - [COOO*] - COO* + O. [ABSTRACT FROM AUTHOR]