Uniaxial pressure applied along a Ru-O-Ru bond direction induces an elliptical distortion of the largest Fermi surface of Sr2RuO4 , eventually causing a Fermi surface topological transition, also ...known as a Lifshitz transition, into an open Fermi surface. There are various anomalies in low-temperature properties associated with this transition, including maxima in the superconducting critical temperature and in resistivity. In the present paper, we report refined measurements of the strain at which this transition occurs, employing apparatus in which the stress on the sample is measured, and resonant ultrasound measurement of the low-temperature elastic moduli. The Lifshitz transition is found to occur at a longitudinal strain ɛxx of (− 0.44 ± 0.06) × 10−2, which corresponds to a B1g strain ɛxx − ɛyy of (− 0.66 ± 0.09) × 10−2 . This is considerably smaller than the strain corresponding to a Lifshitz transition in density functional theory calculations, even if the spin-orbit coupling is taken into account. Using dynamical mean-field theory, we show that electronic correlations reduce the critical strain. It turns out that the orbital anisotropy of the local Coulomb interaction on the Ru site is, furthermore, important to bring this critical strain close to the experimental number and thus well into the experimentally accessible range of strains.
•Clonal yeast populations are extremely heterogeneous in mitochondrial network structure.•AAC2 repression increases mitochondrial ΔΨ and induces mitochondrial fragmentation.•AAC2 repression prevents ...further protonophore-induced mitochondrial fragmentation.•AAC2 is dispensable for mitochondrial fusion in yeast.
The mitochondrial network structure dynamically adapts to cellular metabolic challenges. Mitochondrial depolarisation, particularly, induces fragmentation of the network. This fragmentation may be a result of either a direct regulation of the mitochondrial fusion machinery by transmembrane potential or an indirect effect of metabolic remodelling. Activities of ATP synthase and adenine nucleotide translocator (ANT) link the mitochondrial transmembrane potential with the cytosolic NTP/NDP ratio. Given that mitochondrial fusion requires cytosolic GTP, a decrease in the NTP/NDP ratio might also account for protonophore-induced mitochondrial fragmentation. For evaluating the contributions of direct and indirect mechanisms to mitochondrial remodelling, we assessed the morphology of the mitochondrial network in yeast cells with inhibited ANT. We showed that the repression of AAC2 (PET9), a major ANT gene in yeast, increases mitochondrial transmembrane potential. However, the mitochondrial network in this strain was fragmented. Meanwhile, AAC2 repression did not prevent mitochondrial fusion in zygotes; nor did it inhibit mitochondrial hyperfusion induced by Dnm1p inhibitor mdivi-1. These results suggest that the inhibition of ANT, rather than preventing mitochondrial fusion, facilitates mitochondrial fission. The protonophores were not able to induce additional mitochondrial fragmentation in an AAC2-repressed strain and in yeast cells with inhibited ATP synthase. Importantly, treatment with the ATP synthase inhibitor oligomycin A also induced mitochondrial fragmentation and hyperpolarization. Taken together, our data suggest that ATP/ADP translocation plays a crucial role in shaping of the mitochondrial network and exemplify that an increase in mitochondrial membrane potential does not necessarily oppose mitochondrial fragmentation.
Chemicals inducing a mild decrease in the ATP/ADP ratio are considered as caloric restriction mimetics as well as treatments against obesity. Screening for such chemicals in animal model systems ...requires a lot of time and labor. Here, we present a system for the rapid screening of non-toxic substances causing such a de-energization of cells. We looked for chemicals allowing the growth of yeast lacking trehalose phosphate synthase on a non-fermentable carbon source in the presence of glucose. Under such conditions, the cells cannot grow because the cellular phosphate is mostly being used to phosphorylate the sugars in upper glycolysis, while the biosynthesis of bisphosphoglycerate is blocked. We reasoned that by decreasing the ATP/ADP ratio, one might prevent the phosphorylation of the sugars and also boost bisphosphoglycerate synthesis by providing the substrate, i.e., inorganic phosphate. We confirmed that a complete inhibition of oxidative phosphorylation alleviates the block. As our system includes a non-fermentable carbon source, only the chemicals that did not cause a complete block of mitochondrial ATP synthesis allowed the initial depletion of glucose followed by respiratory growth. Using this system, we found two novel compounds, dodecylmethyl diphenylamine (FS1) and diethyl (tetradecyl) phenyl ammonium bromide (Kor105), which possess a mild membrane-depolarizing activity.
Sterols change the biophysical properties of lipid membranes. Here, we analyzed how sterols affect the activity of widely used antimicrobial membrane-active compounds, sodium dodecyl sulfate (SDS) ...and benzalkonium chloride (BAC). We also tested a novel benzalkonium-like substance, Kor105. Our data suggest that benzalkonium and Kor105 disturb the ordering of the membrane lipid packaging, and this disturbance is dampened by cholesterol. The disturbance induced by Kor105 is stronger than that induced by BAC because of the higher rigidity of the Kor105 molecule due to a shorter linker between the phenyl group and quaternary nitrogen. On the contrary, individual SDS molecules do not cause the disturbance. Thus, in the tested range of concentrations, SDS-membrane interaction is not influenced by cholesterol. To study how sterols influence the biological effects of these chemicals, we used yeast strains lacking Lam1-4 proteins. These proteins transport sterols from the plasma membrane into the endoplasmic reticulum. We found that the mutants are resistant to BAC and Kor105 but hypersensitive to SDS. Together, our findings show that sterols influence the interaction of SDS versus benzalkonium chloride and Kor105 with the membranes in a completely different manner.
Purpose
Accounting for ionic strength and ion association, the degree of calculated supersaturation with CaCO
3
of gleyic solonetz and molic solonetz soil solution is high. The purpose of the ...research was to reveal the effect of the water-dissolved organic matter (DOM) on the calcium carbonate equilibrium (CCE) in soil solution, to create a thermodynamic model of carbonate association and complexation with DOM and heavy metals (HMs), and to correct the principal of soil management.
Materials and methods
Object of research—Kastanozem complex of the dry steppe, Rostov Oblast, Russia. The water extraction of soluble salts was made at the water-to soil-ratio 5:1 and analyzed using standard methods. DOM content was determined by Strosser (J Agrobiol 27:49–60,
2010
). The soil solution macro-ion equilibrium composition was calculated using ION-2 program (Endovitsky et al.
2009
). DOM role in soil solution supersaturation with СаСО
3
was assessed, comparing C content in real solution and in identical artificial solution prepared without organic matter. Taking into account the ion association, the molar fractions of free and bound HM ion were calculated using microelement association coefficient,
k
as(ME)
. The soil liquid-phase saturation with CaCO
3
was characterized by the ratio of the real solubility product (
S
) to the thermodynamic solubility product (
S
0
):
К
=
S
/
S
0
.
Results and discussion
The soil solution supersaturation with CaCO
3
was characterized by the product of analytical concentrations (
S
), equilibrium concentrations accounting ion activity (
S
I
), ion association (
S
II
), ion association and complexation (
S
III
), and the thermodynamic solubility product (
S
0
). To evaluate the role of DOM in soil solution supersaturation with CaCO
3
, the initial pure Ca (HCO
3
)
2
solution series was prepared. The humic and fulvic acids from the illuvial horizon of gleyic solonetz with concentrations of 20 mg C L
−1
and 120 mg C L
−1
decreased the CaCO
3
precipitation compared with initial soil solution. The release of CaCO
3
from soil water extracts containing water-soluble organic matter was 1.2–1.9 times less compared with identical artificial solution not containing organic matter. The HM binding by carbonates is proportional to the DOM content.
Conclusions
In molic solonetz and gleyic solonetz, the neutralization of the soda should be assessed by the soil solution supersaturation with CaCO
3
. To calculate the degree of HM passivation in soil solution containing DOM, the coefficient of soil solution oversaturation with CaCO
3
is proposed. For reducing soil organic matter and DOM mobility and loss from soil, as well as for Pb passivation, intra-soil mechanical processing, intra-soil waste management, and intra-soil watering are proposed.
•PDR5 is essential for resistance to dodecyltriphenylphosphonium.•Dodecyltriphenylphosphonium suppresses yeast multiple drug resistance.•Dodecyltriphenylphosphonium prevents release of Pdr5p ...substrates.
Multiple drug resistance pumps are potential drug targets. Here we asked whether the lipophilic cation dodecyltriphenylphosphonium (C12TPP) can interfere with their functioning. First, we found that suppression of ABC transporter gene PDR5 increases the toxicity of C12TPP in yeast. Second, C12TPP appeared to prevent the efflux of rhodamine 6G – a fluorescent substrate of Pdr5p. Moreover, C12TPP increased the cytostatic effects of some other known Pdr5p substrates. The chemical nature of C12TPP suggests that after Pdr5p-driven extrusion the molecules return to the plasma membrane and then into the cytosol, thus effectively competing with other substrates of the pump.
In the triangular layered magnet PdCrO2 the intralayer magnetic interactions are strong; however, the lattice structure frustrates interlayer interactions. In spite of this, long-range, 120∘ ...antiferromagnetic order condenses at TN=38 K. We show here through neutron scattering measurements under in-plane uniaxial stress and in-plane magnetic field that this occurs through a spontaneous breaking of the threefold rotational symmetry of the nonmagnetic lattice, which relieves the interlayer frustration. We also show through resistivity measurements that uniaxial stress can suppress thermal magnetic disorder within the antiferromagnetic phase.
Cell senescence is dependent on the arrest in cell cycle. Here we studied the role of mitochondrial retrograde response signaling in yeast cell survival under a prolonged arrest. We have found that, ...unlike G1, long-term arrest in mitosis or S phase results in a loss of colony-forming abilities. Consistent with previous observations, loss of mitochondrial DNA significantly increased the survival of arrested cells. We found that this was because the loss increases the duration of G1 phase. Unexpectedly, retrograde signaling, which is typically triggered by a variety of mitochondrial dysfunctions, was found to be a negative regulator of the survival after the release from S-phase arrest induced by the telomere replication defect. Deletion of retrograde response genes decreased the arrest-induced death in such cells, whereas deletion of negative regulator of retrograde signaling MKS1 had the opposite effect. We provide evidence that these effects are due to alleviation of the strength of the S-phase arrest.
Stoichiometric SnTe is theoretically a small gap semiconductor that undergoes a ferroelectric distortion on cooling. In reality however, crystals are always nonstoichiometric and metallic; the ...ferroelectric transition is therefore, more accurately described as a polar structural transition. Here, we study the Fermi surface using quantum oscillations as a function of pressure. We find the oscillation spectrum changes at high pressure due to the suppression of the polar transition and less than 10 kbars is sufficient to stabilize the undistorted cubic lattice, this is accompanied by a large decrease in the Hall and electrical resistivities. Combined with our density functional theory calculations and angle-resolved photoemission spectroscopy measurements, this suggests the Fermi surface L pockets have lower mobility than the tubular Fermi surfaces that connect them. Additionally, we find the unusual phenomenon of a linear magnetoresistance that exists irrespective of the distortion that we attribute to regions of the Fermi surface with high curvature.
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