•This is the first study on long term effects of proton irradiations at FLASH dose rate in vitro.•Proton dose rate has little impact on acute effects in normal cells.•Cell survival and γH2AX foci ...formation depend weakly on proton dose rate.•Protons delivered at FLASH dose rates mitigate long-term adverse effects in normal cells.•Increase in proton dose rate reduces the number of senescent cells and cellular levels of TGFβ1.
Radiotherapy outcomes are limited by toxicity in the healthy tissues surrounding the irradiated tumor. Recent pre-clinical studies have shown that irradiations with electrons or photons delivered at so called FLASH dose rates (i.e. >40 Gy/s) dramatically reduce adverse side effects in the normal tissues while being equally efficient for tumor control as irradiations at conventional dose rates (3–5 cGy/s). In the case of protons however, FLASH effects have not been investigated partially because of the limited availability of facilities that can achieve such high dose rates.
Using a novel irradiation platform, we measured acute and long-term biological effects in normal human lung fibroblasts (IMR90) exposed to therapeutically relevant doses of 4.5 MeV protons (LET = 10 keV/µm) delivered at dose rates spanning four orders of magnitude. Endpoints included clonogenic cell survival, γH2AX foci formation, induction of premature senescence (β-gal), and the expression of the pro-inflammatory marker TGFβ.
Proton dose rate had no influence on the cell survival, but for the highest dose rate used (i.e. 1000 Gy/s) foci formation saturated beyond 10 Gy. In the progeny of irradiated cells, an increase in dose (20 Gy vs. 10 Gy) and dose rate (1000 Gy/s vs. 0.05 Gy/s) positively affected the number of senescence cells and the expression of TGFβ1.
In normal lung fibroblasts proton dose rate had little impact on acute effects, but significantly influenced the expression of long-term biological responses in vitro. Compared to conventional dose rates, protons delivered at FLASH dose rates mitigated such delayed detrimental effects.
Das Wasserstoffbrennen in der Sonne wird von der sogenannten Proton‐Proton‐Kette bestimmt. Ein zweiter, parallel ablaufender Prozess ist der Bethe‐Weizsäcker‐ oder CNO‐Zyklus. Bei der Sonne trägt er ...nur etwa 0,8 % zur Energieerzeugung bei, kann aber zur Bestimmung der Kohlenstoffhäufigkeit im Sonneninnern genutzt werden. Neue Labordaten zur ersten Reaktion im Zyklus zeigen für massereiche Sterne eine 25 % geringere Rate als bislang angenommen, während sich für unsere Sonne wenig ändert.
Cytochromec oxidase (CcO) is a redox-driven proton pump that powers aerobic respiratory chains. We show here by multi-scale molecular simulations that a protonated water cluster near the active site ...is likely to serve as the transient proton-loading site (PLS) that stores a proton during the pumping process. The pKa of this water cluster is sensitive to the redox states of the enzyme, showing distinct similarities to other energy converting proton pumps.
Spontaneous and stimulated emission (SE) of thin Cu(In,Ga)Se.sub.2 films, deposited on sodium-containing glass substrates and irradiated by protons with an energy of 2.5 keV and doses of ...10.sup.14-10.sup.17 cm.sup.-2, were investigated upon excitation by nanosecond laser pulses with the power density from 5 to 100 kW/cm.sup.2. An increase in the intensity and a decrease in the SE appearance threshold were found for the films irradiated by protons with doses of 10.sup.14-10.sup.15 cm.sup.-2, in comparison with nonirradiated films. An increase in the SE threshold and a decrease in the intensity of SE and spontaneous emission were observed at the irradiation dose of 10.sup.16 cm.sup.-2. After a dose of 10.sup.17 cm.sup.-2 the intensity of emission decreased sharply and the SE threshold was not reached. Possible reasons of the observed effects are discussed.
Despite diverse and changing extracellular environments, fungi maintain a relatively constant cytosolic pH and numerous organelles of distinct lumenal pH. Key players in fungal pH control are ...V-ATPases and the P-type proton pump Pma1. These two proton pumps act in concert with a large array of other transporters and are highly regulated. The activities of Pma1 and the V-ATPase are coordinated under some conditions, suggesting that pH in the cytosol and organelles is not controlled independently. Genomic studies, particularly in the highly tractable S. cerevisiae, are beginning to provide a systems-level view of pH control, including transcriptional responses to acid or alkaline ambient pH and definition of the full set of regulators required to maintain pH homeostasis. Genetically encoded pH sensors have provided new insights into localized mechanisms of pH control, as well as highlighting the dynamic nature of pH responses to the extracellular environment. Recent studies indicate that cellular pH plays a genuine signaling role that connects nutrient availability and growth rate through a number of mechanisms. Many of the pH control mechanisms found in S. cerevisiae are shared with other fungi, with adaptations for their individual physiological contexts. Fungi deploy certain proton transport and pH control mechanisms not shared with other eukaryotes; these regulators of cellular pH are potential antifungal targets. This review describes current and emerging knowledge proton transport and pH control mechanisms in S. cerevisiae and briefly discusses how these mechanisms vary among fungi.
Ionic liquid-salt based aqueous biphasic systems (ABS) are examples of ABS of salt-salt combination. In the present study, ABS composed of water soluble ionic liquid (IL) 1-butyl-3-methylimidazolium ...chloride (bmimCl) and kosmotropic salts K.sub.3PO.sub.4, K.sub.2CO.sub.3 were applied in the separation of no-carrier-added (NCA) .sup.195(m,g),197mHg radionuclides from bulk Au target. The .sup.195(m,g),197mHg radionuclides were produced by irradiating gold foil with 23 MeV protons. NCA Hg radionuclides were extracted into the IL phase leaving bulk Au in the salt rich phase. At the optimized condition high separation factors, 3.5 x 10.sup.4 and 5.5 x 10.sup.4 were obtained when K.sub.3PO.sub.4 and K.sub.2CO.sub.3 were used as salt rich phase.
Electrogenic proton pumps have been implicated in the generation of slow wave potentials (SWPs), damage-induced membrane depolarizations that activate the jasmonate (JA) defense pathway in leaves ...distal to wounds. However, no defined H⁺-ATPases have been shown to modulate these electrical signals. Pilot experiments revealed that the proton pump activator fusicoccin attenuated SWP duration in Arabidopsis. Using mutant analyses, we identified Arabidopsis H⁺-ATPase 1 (AHA1) as a SWP regulator. The duration of the repolarization phase was strongly extended in reduced function aha1 mutants. Moreover, the duration of SWP repolarization was shortened in the presence of a gain-of-function AHA1 allele. We employed aphid electrodes to probe the effects of the aha1 mutation on wound-stimulated electrical activity in the phloem. Relative to the wild type, the aha1-7 mutant increased the duration and reduced the amplitudes of electrical signals in sieve tube cells. In addition to affecting electrical signaling, expression of the JA pathway marker gene JAZ10 in leaves distal to wounds was enhanced in aha1-7. Consistent with this, levels of wound-response jasmonoyl-isoleucine were enhanced in the mutant, as was defense against a lepidopteran herbivore. The work identifies a discrete member of the P-type ATPase superfamily with a role in leaf-to-leaf electrical signaling and plant defense.
The passage of protons across membranes through F1Fo-ATP synthases spins their rotors and drives the synthesis of ATP. While the principle of torque generation by proton transfer is known, the ...mechanisms and routes of proton access and release and their evolution are not fully understood. Here, we show that the entry site and path of protons in the lumenal half channel of mitochondrial ATP synthases are largely defined by a short N-terminal α-helix of subunit-a. In Trypanosoma brucei and other Euglenozoa, the α-helix is part of another polypeptide chain that is a product of subunit-a gene fragmentation. This α-helix and other elements forming the proton pathway are widely conserved across eukaryotes and in Alphaproteobacteria, the closest extant relatives of mitochondria, but not in other bacteria. The α-helix blocks one of two proton routes found in Escherichia coli, resulting in a single proton entry site in mitochondrial and alphaproteobacterial ATP synthases. Thus, the shape of the access half channel predates eukaryotes and originated in the lineage from which mitochondria evolved by endosymbiosis.
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