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One (1P), two (2P), three (3P) or four (4P) pulses of light supplied by a xenon lamp, were applied to young lettuce plants grown in pots. The lamp used in the trial was similar to those used for fruit surface sterilization. Total flavonols were measured in leaves using the Dualex method. In a first trial conducted in greenhouse conditions, 6 days after the pulsed light (PL) treatment, flavonols were increased by 312% and 525% in the 3P and 4P treatments, respectively, in comparison to the those in the untreated control. Changes in the chlorophyll fluorescence parameters suggest that the PL treatment may induce limited and transient damage to the photosynthetic machinery and that the damage increases with the increasing number of pulses. The performance parameters were not significantly affected by PL and recovered fully by 6 days after the treatments. The 1P and the 2P treatments 6 days after the treatment showed a 28.6% and a 32.5% increase, respectively, in net photosynthetic assimilation, when compared to that of the control. However, 8 days after the treatment, there was no longer a difference between the treatments and the control in net photosynthetic assimilation. Eight days after the light treatment, the 3P treatment showed a 38.4% increase in maximal net photosynthetic assimilation over that of the control, which is an indication of positive long-term adaptation of photosynthetic capacity. As a whole, our observations suggest that PL could be used on field or greenhouse crops to increase their phytochemical content. No long-lasting or strong negative effects on photosynthesis were associated with PL within the range of doses we tested; some observations even suggest that certain treatments could result in an additional positive effect. This conclusion is supported by a second trial conducted in phytotrons. More studies are required to better understand the roles of the different wavelengths supplied by PL and their interactions.

Studies of the Earth's atmosphere have shown that more than 90% of the expected amount of Xe is depleted, a finding often referred to as the ‘missing Xe paradox’. Although several models for a Xe reservoir have been proposed, whether the missing Xe could be contained in the Earth's inner core has not yet been answered. The key to addressing this issue lies in the reactivity of Xe with Fe/Ni, the main constituents of the Earth's core. Here, we predict, through first-principles calculations and unbiased structure searching techniques, a chemical reaction of Xe with Fe/Ni at the temperatures and pressures found in the Earth's core. We find that, under these conditions, Xe and Fe/Ni can form intermetallic compounds, of which XeFe 3 and XeNi 3 are energetically the most stable. This shows that the Earth's inner core is a natural reservoir for Xe storage and provides a solution to the missing Xe paradox. Studies of the Earth's atmosphere have shown that more than 90% of xenon is depleted — the so-called missing Xe paradox. Now a theoretical study shows that Xe and Fe/Ni can form inter-metallic compounds of XeFe 3 and XeNi 3 under conditions found in the Earth's inner core, and could provide a solution to the puzzle.

Magnetic resonance imaging (MRI) enables high-resolution non-invasive observation of the anatomy and function of intact organisms. However, previous MRI reporters of key biological processes tied to gene expression have been limited by the inherently low molecular sensitivity of conventional 1 H MRI. This limitation could be overcome through the use of hyperpolarized nuclei, such as in the noble gas xenon, but previous reporters acting on such nuclei have been synthetic. Here, we introduce the first genetically encoded reporters for hyperpolarized 129 Xe MRI. These expressible reporters are based on gas vesicles (GVs), gas-binding protein nanostructures expressed by certain buoyant microorganisms. We show that GVs are capable of chemical exchange saturation transfer interactions with xenon, which enables chemically amplified GV detection at picomolar concentrations (a 100- to 10,000-fold improvement over comparable constructs for 1 H MRI). We demonstrate the use of GVs as heterologously expressed indicators of gene expression and chemically targeted exogenous labels in MRI experiments performed on living cells. Magnetic resonance imaging of gene expression has been limited by the low molecular sensitivity of conventional 1 H-MRI. To overcome this limitation, the first genetically encoded reporters for hyperpolarized xenon MRI have been developed. These expressible reporters, based on gas-filled protein nanostructures from buoyant microorganisms, are detectable at picomolar concentrations.

Nanomechanical resonators have been used to weigh cells, biomolecules and gas molecules 1 , 2 , 3 , 4 , and to study basic phenomena in surface science, such as phase transitions 5 and diffusion 6 , 7 . These experiments all rely on the ability of nanomechanical mass sensors to resolve small masses. Here, we report mass sensing experiments with a resolution of 1.7 yg (1 yg = 10 −24  g), which corresponds to the mass of one proton. The resonator is a carbon nanotube of length ∼150 nm that vibrates at a frequency of almost 2 GHz. This unprecedented level of sensitivity allows us to detect adsorption events of naphthalene molecules (C 10 H 8 ), and to measure the binding energy of a xenon atom on the nanotube surface. These ultrasensitive nanotube resonators could have applications in mass spectrometry, magnetometry and surface science. A carbon nanotube resonator is used to form the basis of an ultrasensitive mass sensor that can also be employed to study basic phenomena in surface science.

Xenon isotopic analysis shows that ancient pockets of water found in a mine in Timmins, Canada, have survived in the Earth’s crust for at least 1.5 billion years. Water from the deep past The deep continental crust contains water-filled fractures that can preserve a record of fluid chemistry and environmental conditions at the time of isolation. This paper reports noble gas isotopic compositions from bulk fracture fluids located 2.4 km below the surface in 2.7-billion-year-old rocks in the Timmins mine in Ontario, Canada. The isotope data indicate that some of these ancient pockets of water have remained isolated in the crust for between 1.5 and 2.64 billion years. The gas in this water — the oldest 'free fluid' ever found — is a mixture of hydrogen, helium, methane and nitrogen. The authors speculate that these ancient fluid environments may be capable of supporting life. Fluids trapped as inclusions within minerals can be billions of years old and preserve a record of the fluid chemistry and environment at the time of mineralization 1 , 2 , 3 . Aqueous fluids that have had a similar residence time at mineral interfaces and in fractures (fracture fluids) have not been previously identified. Expulsion of fracture fluids from basement systems with low connectivity occurs through deformation and fracturing of the brittle crust 4 . The fractal nature of this process must, at some scale, preserve pockets of interconnected fluid from the earliest crustal history. In one such system, 2.8 kilometres below the surface in a South African gold mine, extant chemoautotrophic microbes have been identified in fluids isolated from the photosphere on timescales of tens of millions of years 5 . Deep fracture fluids with similar chemistry have been found in a mine in the Timmins, Ontario, area of the Canadian Precambrian Shield. Here we show that excesses of 124 Xe, 126 Xe and 128 Xe in the Timmins mine fluids can be linked to xenon isotope changes in the ancient atmosphere 2 and used to calculate a minimum mean residence time for this fluid of about 1.5 billion years. Further evidence of an ancient fluid system is found in 129 Xe excesses that, owing to the absence of any identifiable mantle input, are probably sourced in sediments and extracted by fluid migration processes operating during or shortly after mineralization at around 2.64 billion years ago. We also provide closed-system radiogenic noble-gas ( 4 He, 21 Ne, 40 Ar, 136 Xe) residence times. Together, the different noble gases show that ancient pockets of water can survive the crustal fracturing process and remain in the crust for billions of years.

Xenon, which is quite inert under ambient conditions, may become reactive under pressure. The possibility of the formation of stable xenon oxides and silicates in the interior of the Earth could explain the atmospheric missing xenon paradox. Using an ab initio evolutionary algorithm, we predict the existence of thermodynamically stable Xe–O compounds at high pressures (XeO, XeO 2 and XeO 3 become stable at pressures above 83, 102 and 114 GPa, respectively). Our calculations indicate large charge transfer in these oxides, suggesting that large electronegativity difference and high pressure are the key factors favouring the formation of xenon compounds. However, xenon compounds cannot exist in the Earth's mantle: xenon oxides are unstable in equilibrium with the metallic iron occurring in the lower mantle, and xenon silicates are predicted to decompose spontaneously at all mantle pressures (<136 GPa). However, it is possible that xenon atoms may be retained at defects in mantle silicates and oxides. Xenon is an inert element at ambient conditions but may become reactive under pressure. It has now been predicted that pressure stabilizes increasing oxidation states of Xe atoms (from Xe 0 to Xe 2+ to Xe 4+ to Xe 6+ ), and thus a series of compounds — XeO, XeO 2 and XeO 3 — become thermodynamically stable at megabar pressures.

Cryo focused ion beam lamella preparation is a potent tool for in situ structural biology, enabling the study of macromolecules in their native cellular environments. However, throughput is currently limited, especially for thicker, more biologically complex samples. We describe how xenon plasma focused ion beam milling can be used for routine bulk milling of thicker, high-pressure frozen samples. We demonstrate lamellae preparation with a high success rate on these samples and determine a 4.0 Å structure of the Escherichia coli ribosome on these lamellae using sub volume averaging. We determine the effects on sample integrity of increased ion currents up to 60 nA during bulk milling of thicker planar samples, showing no measurable damage to macromolecules beyond an amorphous layer on the backside of the lamellae. The use of xenon results in substantial structural damage to particles up to approximately 30 nm in depth from the milled surfaces, and the effects of damage become negligibly small by 45 nm. Our results outline how the use of high currents using xenon plasma focused ion beam milling may be integrated into FIB milling regimes for preparing thin lamellae for high-resolution in situ structural biology. Here the authors demonstrate that Xenon plasma can shape thick frozen-hydrated biological samples for structure determination of molecules in the cellular context and demonstrating the potential of the technique to be used on more complex samples.

Noble gas (or aerogen) bond (NgB) can be outlined as the attractive interaction between an electron-rich atom or group of atoms and any element of Group-18 acting as an electron acceptor. The IUPAC already recommended systematic nomenclature for the interactions of groups 17 and 16 (halogen and chalcogen bonds, respectively). Investigations dealing with noncovalent interactions involving main group elements (acting as Lewis acids) have rapidly grown in recent years. They are becoming acting players in essential fields such as crystal engineering, supramolecular chemistry, and catalysis. For obvious reasons, the works devoted to the study of noncovalent Ng-bonding interactions are significantly less abundant than halogen, chalcogen, pnictogen, and tetrel bonding. Nevertheless, in this short review, relevant theoretical and experimental investigations on noncovalent interactions involving Xenon are emphasized. Several theoretical works have described the physical nature of NgB and their interplay with other noncovalent interactions, which are discussed herein. Moreover, exploring the Cambridge Structural Database (CSD) and Inorganic Crystal Structure Database (ICSD), it is demonstrated that NgB interactions are crucial in governing the X-ray packing of xenon derivatives. Concretely, special attention is given to xenon fluorides and xenon oxides, since they exhibit a strong tendency to establish NgBs.

Like all noble gases, xenon is colourless, odourless and inflammable — but it is also more reactive, and much rarer, than its lighter relatives. Ivan Dmochowski ponders how xenon, though initially slow to earn a spot in the periodic table, is now at the forefront of advances in science and technology.

Closed electron shell systems, such as hydrogen, nitrogen or group 18 elements, can form weakly bound stoichiometric compounds at high pressures. An understanding of the stability of these van der Waals compounds is lacking, as is information on the nature of their interatomic interactions. We describe the formation of a stable compound in the Xe–H 2 binary system, revealed by a suite of X-ray diffraction and optical spectroscopy measurements. At 4.8 GPa, a unique hydrogen-rich structure forms that can be viewed as a tripled solid hydrogen lattice modulated by layers of xenon, consisting of xenon dimers. Varying the applied pressure tunes the Xe–Xe distances in the solid over a broad range from that of an expanded xenon lattice to the distances observed in metallic xenon at megabar pressures. Infrared and Raman spectra indicate a weakening of the intramolecular covalent bond as well as persistence of semiconducting behaviour in the compound to at least 255 GPa. Both hydrogen and xenon form unusual phases at very high pressures. Researchers have now observed that an unexpectedly stable compound forms when a hydrogen-rich mixture of the two gases is subjected to pressures in the gigapascal range. Xenon dimers and other unusual bonding states are revealed in this compound, which is stable to megabar pressures.