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Turin, L.

Publications and source records attributed to Turin, L..

6 recordsLinked to original sources

A candidate electromagnetic channel for coordination between physicallyseparated Drosophila

While filming Drosophila melanogaster recovering together from xenon anesthesia, we noticed frequent synchronous pauses in flies recovering in the same chamber. To ask whether such coordination could survive physical separation of the animals, we housed flies individually in the opaque wells of a multi-well plate, with no visual or tactile contact. They still coordinated the magnitude of their movements around a shared light*dark startle more closely than the shared stimulus alone can explain. We isolate this excess coordination with a measure that subtracts the stimulus-driven component by comparing movements within versus across transitions. A complementary common-mode statistic shows that flies also remain weakly but reproducibly correlated away from the transitions. The tested conventional channels do not readily account for the effect: vision is excluded by the opaque walls, and self-generated substrate vibration is disfavored for the background common mode because coordination does not scale with movement amplitude and persists when the continuous side-wall path between wells is interrupted by air gaps. The transition signal declined across the material series from plastic toward aluminum. This paNern is not a simple metal-versus-nonmetal split. It is consistent with material-dependent near-field magnetic radiofrequency coupling through the well geometry and transparent imaging aperture. Vector-network measurements also indicate that near-field inter- well coupling differs between steel and aluminum. We have previously shown that Drosophila emit spontaneous, metabolically powered magnetic radiofrequency radiation that tracks nervous-system activity. Together these results are consistent with a near-field magnetic emission that can leak between separated individuals. We discuss radical-pair detection, possible emission mechanisms, and experiments needed to identify the carrier frequency, detector, and biological role. SignificanceFruit flies housed in separate, opaque chambers that block sight and touch nonetheless coordinate their movements. The coordination persists when mechanical vibration paths between chambers are cut. The coordination is absent when the plate is made of aluminum, and intermediate in size when the plate is made of ferromagnetic steel. This ordering, together with direct RF-coupling measurements, points to a near-field magnetic radiofrequency signal passing between individuals, though the carrier frequency and detector remain unknown. Because flies are already known to emit faint, metabolically powered radiofrequency fields that track nervous-system activity, these results raise the possibility that nervous systems both emit and detect such fields. If confirmed, this would identify an unrecognized magnetic radiofrequency channel in animal biology and suggest that brains are less electromagnetically private than assumed.

neuroscience↗

A chance insight into the mechanism of phosgene toxicity

It has long been known that phosgene, a war gas and an industrial reagent, causes intense oxidative stress, but how it does so remains unclear. Here we report an accidental discovery: Electron spin resonance spectroscopy (ESR) of live fruit flies reveals that phosgene exposure results in a distinctive manganese (II) hyperfine structure. After exposure to phosgene, every batch of flies consistently displays the Mn (II) signal. Regardless of the aftercare provided, these flies inevitably perish, making the signal a diagnostic of phosgene poisoning in flies. The intensity of the signal is dependent on both exposure time and concentration, resembling the kinetics of phosgene poisoning. The signal of Mn (II) correlates with the presence of a functional superoxide dismutase Sod2. After exposure, heterozygous Sod2 mutants have a markedly lower intensity of Mn (II) in their ESR spectrum. We suggest that phosgene disturbs Mn redox cycling between ESR-silent Mn (III) and ESR-active Mn (II) that is required for superoxide dismutation. Accordingly, mitochondria of phosgene-treated flies show reduced rates of hydrogen peroxide production, and severely compromised complex I-linked respiration. It is likely that phosgene damages mitochondria through MnSOD and complex I, which contributes to its toxicity. This work uses Drosophila melanogaster for the first time in phosgene research.

pharmacology and toxicology↗

Free radical production induced by visible light in live fruit flies

Visible light triggers free radical production in alive and intact Drosophila melanogaster. We exposed fruit flies to red (613-631 nm), green (515-535 nm), and blue (455-475 nm) light while we monitored changes in unpaired electron content with an electron spin resonance spectrometer (ESR/EPR). The immediate response to light is a rapid increase in spin content lasting approximately 10 seconds followed by a slower, linear increase for approximately 170 seconds. When the light is turned off, the spin population promptly decays with a similar time course, though never fully returning to baseline. The magnitude and time course of the spin production depends on the wavelength of the light. Initially, we surmised that eumelanin might be responsible for the spin change because of its documented ability for visible light absorption and its highly stable free radical content. To explore this, we utilized different fruit fly strains with varying eumelanin content and clarified the relation of melanin types with the spin response. Our findings revealed that flies with darker cuticle have at least three-fold more unpaired electrons than flies with yellow cuticle. However, to our surprise, the increase in unpaired electron population by light was not drastically different amongst the genotypes. This suggests that light-induced free radical production may not exclusively rely on the presence of black melanin, but may instead be dependent on light effects on quinone-based cuticular polymers.

biophysics↗

A Possible Unitary Mechanism for General Anesthesia

The oxygen reduction reaction (ORR) is of high importance, among others because of its role in cellular respiration and in the operation of fuel cells. Recently, a possible relation between respiration and general anesthesia has been found. This work aims to explore whether anesthesia related gases affect the ORR. In ORR, oxygen which is in its triplet ground state is reduced to form products that are all in the singlet state. While this process is "in principle" forbidden because of spin conservation, it is known that if the electrons transferred in the ORR are spin polarized, the reaction occurs efficiently. Here we show, in electrochemical experiments, that the efficiency of the oxygen reduction is reduced by the presence of general anesthetics in solution. We suggest that a spin-orbit coupling to the anesthetics depolarizes the spins. This causes both a reduction in reaction efficiency and a change in the reaction products. The findings may point to a possible relation between ORR efficiency and anesthetic action. TOC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/518334v2_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@4a5b8aorg.highwire.dtl.DTLVardef@1bfc961org.highwire.dtl.DTLVardef@3e002corg.highwire.dtl.DTLVardef@7d74f0_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

Evidence for Free Radical Drug Ligands in class A G-protein Coupled Receptors

We analyse the conformation of 22 cationic ligands bound to G-protein coupled receptors of known structure and find three ligands that are present inside receptors not in their closed shell cation form, but as neutral radicals, i.e. after addition of an electron to the ligand. The implications of this finding for GPCR function are discussed and a possible experimental test is proposed.

pharmacology and toxicology↗

Gated electron transport in rhodopsin and its relevance to GPCR activation

We identify, by density-functional theory calculations, an electron donor-bridge-acceptor (DBA) complex within the highest resolution X-ray diffraction structures of rhodopsin. The donor is a conserved tryptophan, the acceptor is a zinc ion surrounded by a tryptophan, a histidine and a conserved glutamate. The unusual environment of the zinc ion confers high electron affinity on the zinc site. The bridge is the retinal which can exist either in the neutral aldimine (Schiffs base) or aldiminium (protonated) state. When the retinal is unprotonated, no electron transfer occurs. Upon protonation of the aldimine, the DBA complex conducts and a full electron charge is transferred from donor tryptophan to the zinc complex. This gated electron transfer creates the molecular equivalent of a tunnel triode. Since rhodopsin is the ancestor of GPCRs, we discuss the possible relevance of this gated electron transport to other GPCRs, in particular to olfactory receptors which have been proposed to use an electron tunneling mechanism to detect molecular vibrations.

biophysics↗