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A diet rich in C-3 plants reveals the sensitivity of an alpine mammal to climate change
No full textPlant-herbivore interactions provide critical insights into the mechanisms that govern the spatiotemporal distributions of organisms. These interactions are crucial to understanding the impacts of climate change, which are likely to have an effect on the population dynamics of alpine herbivores. The Royle's pika (Ochotona roylei, hereafter pika) is a lagomorph found in the western Himalaya and is dependent on alpine plants that are at risk from climate change. As the main prey of many carnivores in the region, the pika plays a crucial role in trophic interactions. We examined topographical features, plant genera presence and seasonal dynamics as drivers of the plant richness in the pika's diet across an elevational gradient (2,600-4,450 m). We identified 79 plant genera in the faecal pellets of pikas, of which 89% were forbs, >60% were endemic to the Himalaya, and 97.5% of the diet plant genera identified followed the C-3 photosynthetic pathway. We found that, during the premonsoon season, the number of genera in the pika's diet decreased with increasing elevation. We demonstrate that a large area of talus supports greater plant diversity and, not surprisingly, results in higher species richness in the pika's diet. However, in talus habitat with deep crevices, pikas consumed fewer plant genera suggesting they may be foraging suboptimally due to predation risk. The continued increase in global temperature is expected to have an effect on the distribution dynamics of C-3 plants and consequently influence pika diet and distribution, resulting in a significant negative cascading effect on the Himalayan ecosystem
Insight into the effect of Ti-addition on diffusion-controlled growth and texture of Nb 3 Sn intermetallic superconductor phase
No full textThe alloying of Ti with Cu(Sn) and Nb significantly increases the grain boundary diffusion-controlled growth kinetics of Nb 3 Sn accompanied with a decrease in the activation energy in the Cu(5.5 at. Sn, Ti)/Nb and Cu(5.5 at. Sn)/Nb(Ti) diffusion couples. In either case, the β-(Ti,Nb) precipitates form at the grain boundaries of Nb 3 Sn. On the other hand, the ternary intermetallic phase, Nb 3 Sn 2 Ti 3 , is present in the interior of the Nb 3 Sn phase matrix only when Ti is added to Nb. The pinning forces on the grain boundaries of Nb 3 Sn exhorted by the β-(Ti,Nb) precipitates and related microstructure refinement results in an enhanced growth kinetics of the product phase, Nb 3 Sn. The addition of 0.5 at. Ti to Cu(Sn) has a stronger influence on the growth kinetics and the activation energy for the growth of Nb 3 Sn compared to 3 at. Ti to Nb owing to a higher fraction of smaller and equiaxed grains with high angle grain boundaries of Nb 3 Sn. The Ti-free Nb 3 Sn phase layer grows with a weak texture, a commonly observed behavior in other material systems for the product phases grown by diffusion-controlled mechanism in the interdiffusion zone. On the contrary, a very strong crystallographic texture of the Ti-containing product phase, Nb 3 Sn, is reported that has a unique pattern depending on the orientation of the adjacent Nb or Nb(Ti) grains. The Cu atoms segregate to the grain boundaries of Nb 3 Sn over a distance of �2�5 nm with a depletion of Nb. © 201
D-0-Meson R-AA in PbPb Collisions at root s(NN)=5.02 TeV and Elliptic Flow in pPb Collisions at root s(NN)=8.16 TeV with CM
No full textThe study of charm production in heavy-ion collisions is considered an excellent probe for the properties of the hot and dense medium created in heavy-ion collisions. Measurements of D-0-meson nuclear modification factor can provide strong constraints into the mechanisms of in-medium energy loss and charm flow in the medium. The measurement of D-0-meson elliptic flow in pPb collisions helps us understand the strength of charm quarks coupling to significantly reduced systems which demonstrate hydrodynamic properties. In this paper, the measurements of the D-0-meson nuclear modification factor in PbPb collisions at 5.02 TeV together with the new measurement of D-0-meson elliptic flow in high multiplicity pPb collisions at 5.02 TeV using the two-particle correlation method will be presented
Evidence for light-by-light scattering in ultraperipheral PbPb collisions at root S-NN=5.02 TeV
No full textEvidence for light-by-light (LbL) scattering, gamma gamma -> gamma gamma, in ultraperipheral PbPb collisions at a nucleon-nucleon center of-mass energy of 5.02 TeV is reported. LbL scattering processes are selected in events with just two photons produced, with transverse energy E-T(gamma) > 2 GeV, pseudorapidity vertical bar eta(gamma)vertical bar < 2.4; and diphoton invariant mass m(gamma gamma) > 5 GeV, transverse momentum p(T)(gamma gamma) < 1 GeV, and acoplanarity (1 - Delta phi(gamma gamma)/pi) < 0.01. After all selection criteria, 14 events are observed, compared to 11.1 +/- 1.1 (theo) and 3.8 +/- 1.3 (stat) events expected for signal and background processes respectively. The significance of the signal excess over the background-only hypothesis is 4.10 sigma. The measured fiducial LbL scattering cross section, sigma(fid)(gamma gamma -> gamma gamma) = 122 +/- 46 (stat) +/- 29 (syst) +/- 4 (theo) nb is consistent with the standard model prediction
Selectivity among Anti-� Factors by Mycobacterium tuberculosis ClpX Influences Intracellular Levels of Extracytoplasmic Function � Factors
No full textExtracytoplasmic function � factors that are stress inducible are often sequestered in an inactive complex with a membrane-associated anti-� factor. Mycobacterium tuberculosis membrane-associated anti-� factors have a small, stable RNA gene A (ssrA)-like degron for targeted proteolysis. Interaction between the unfoldase, ClpX, and a substrate with an accessible degron initiates energy-dependent proteolysis. Four anti-� factors with a mutation in the degron provided a set of natural substrates to evaluate the influence of the degron on degradation strength in ClpX-substrate processivity. We note that a point mutation in the degron (X-Ala-Ala) leads to an order-of-magnitude difference in the dwell time of the substrate on ClpX. Differences in ClpX/anti-� interactions were correlated with changes in unfoldase activities. Green fluorescent protein (GFP) chimeras or polypeptides with a length identical to that of the anti-� factor degron also demonstrate degron-dependent variation in ClpX activities. We show that degron-dependent ClpX activity leads to differences in anti-� degradation, thereby regulating the release of free � from the �/anti-� complex. M. tuberculosis ClpX activity thus influences changes in gene expression by modulating the cellular abundance of ECF � factors.IMPORTANCE The ability of Mycobacterium tuberculosis to quickly adapt to changing environmental stimuli occurs by maintaining protein homeostasis. Extracytoplasmic function (ECF) � factors play a significant role in coordinating the transcription profile to changes in environmental conditions. Release of the � factor from the anti-� is governed by the ClpXP2P1 assembly. M. tuberculosis ECF anti-� factors have an ssrA-like degron for targeted degradation. A point mutation in the degron leads to differences in ClpX-mediated proteolysis and affects the cellular abundance of ECF � factors. ClpX activity thus synchronizes changes in gene expression with environmental stimuli affecting M. tuberculosis physiology. Copyright © 2019 American Society for Microbiology
Evidence of adaptive modulation and magnetic field induced reorientation of variants in epitaxially grown Ni-Mn-Ga thin film on Al 2 O 3 (112¯0) substrate
No full textEpitaxial Ni-Mn-Ga thin films with a room temperature martensite phase were fabricated on single crystal Al 2 O 3 (112¯0) substrate using direct current (DC) magnetron sputtering. The X-ray pole figure measurements confirm the epitaxial relationship of Ni-Mn-Ga (101) 7M || Al 2 O 3 (112¯0) and Ni-Mn-Ga 101¯ 7M || Al 2 O 3 11¯01 between the film and substrate. Transmission electron microscopy reveals the presence of (220) micro-twins at an angle of 62.5° and 56.3° with respect to (202) growth plane. Coexistence of non-modulated martensite phase (a NM = 5.45 à and c NM = 6.56 à ) and seven modulated martensite phases (a 14M =6.26à ,b 14M =5.89à andc 14M =5.56à ) has been observed in the film. The in-situ high-temperature X-ray diffraction indicates reversible thermal phase transformation in the film with a very low thermal hysteresis. The magnetic field induced reorientation (MIR) effect is displayed by the film. © 201
Metal-Organic Self-Assembled Trefoil Knots for C - Br Bond Activation
No full textSynthesizing molecular knots that mimic the catalytic functionality of stereospecific or stereoselective enzymes are an intriguing task in chemistry. Synthetic anion receptors even with moderate halide binding affinities may catalyze chemical reactions involving carbon-halogen bond cleavage. Herein we report isostructural self-assembled trefoil molecular knots (Cu-TK, Cd-TK, Zn-TK) based on Cu(II), Cd(II), and Zn(II) that are capable of binding and stabilizing bromide within their central cavity and are capable of catalyzing C-Br bond cleavage. We also describe the role of noncovalent interactions between the knots and bromide as well as the size and shape of the knots on their catalytic efficiency. Among the studied three knots, Cu-TK was found to be more effective than Zn-TK and Cd-TK in catalyzing C-Br bond cleavage. The catalytic efficiency of the knots toward C-Br bond cleavage was found to be related to a balance between their attractive electrostatic interactions with bromide as well as cavity size and shape of the knots. © 2019 American Chemical Society
Effect of ethanol on insulin dimer dissociation
No full textInsulin-dimer dissociation is an essential biochemical process required for the activity of the hormone. We investigate this dissociation process at the molecular level in water and at the same time, in 5 and 10 water-ethanol mixtures. We compute the free energy surface of the protein dissociation processes by employing biased molecular dynamics simulation. In the presence of ethanol (EtOH), we observe a marked lowering in the free energy barrier of activation of dimer dissociation from that in the neat water, by as much as �50, even in the 5 water-ethanol solution. In addition, ethanol is found to induce significant changes in the dissociation pathway. We extract the most probable conformations of the intermediate states along the minimum energy pathway in the case of all the three concentrations (EtOH mole fractions 0, 5, and 10). We explore the change in microscopic structures that occur in the presence of ethanol. Interestingly, we discover a stable intermediate state in the water-ethanol binary mixture where the centers of the monomers are separated by about 3 nm and the contact order parameter is close to zero. This intermediate is stabilized by the wetting of the interface between the two monomers by the preferential distribution of ethanol and water molecules. This wetting serves to reduce the free energy barrier significantly and thus results in an increase in the rate of dimer dissociation. We also analyze the solvation of the two monomers during the dissociation and both the proteins' departure from the native state configuration to obtain valuable insights into the dimer dissociation processes. © 2019 Author(s)
Structural and Dynamical Order of a Disordered Protein: Molecular Insights into Conformational Switching of PAGE4 at the Systems Level
No full textFolded proteins show a high degree of structural order and undergo (fairly constrained) collective motions related to their functions. On the other hand, intrinsically disordered proteins (IDPs), while lacking a well-defined three-dimensional structure, do exhibit some structural and dynamical ordering, but are less constrained in their motions than folded proteins. The larger structural plasticity of IDPs emphasizes the importance of entropically driven motions. Many IDPs undergo function-related disorder-to-order transitions driven by their interaction with specific binding partners. As experimental techniques become more sensitive and become better integrated with computational simulations, we are beginning to see how the modest structural ordering and large amplitude collective motions of IDPs endow them with an ability to mediate multiple interactions with different partners in the cell. To illustrate these points, here, we use Prostate-associated gene 4 (PAGE4), an IDP implicated in prostate cancer (PCa) as an example. We first review our previous efforts using molecular dynamics simulations based on atomistic AWSEM to study the conformational dynamics of PAGE4 and how its motions change in its different physiologically relevant phosphorylated forms. Our simulations quantitatively reproduced experimental observations and revealed how structural and dynamical ordering are encoded in the sequence of PAGE4 and can be modulated by different extents of phosphorylation by the kinases HIPK1 and CLK2. This ordering is reflected in changing populations of certain secondary structural elements as well as in the regularity of its collective motions. These ordered features are directly correlated with the functional interactions of WT-PAGE4, HIPK1-PAGE4 and CLK2-PAGE4 with the AP-1 signaling axis. These interactions give rise to repeated transitions between (high HIPK1-PAGE4, low CLK2-PAGE4) and (low HIPK1-PAGE4, high CLK2-PAGE4) cell phenotypes, which possess differing sensitivities to the standard PCa therapies, such as androgen deprivation therapy (ADT). We argue that, although the structural plasticity of an IDP is important in promoting promiscuous interactions, the modulation of the structural ordering is important for sculpting its interactions so as to rewire with agility biomolecular interaction networks with significant functional consequences
New Occurrence of Sapphirine-spinel-bearing Granulite from NW of Chilka Lake, Eastern Ghats Belt, Odisha
No full textA new locality of sapphirine-spinel-bearing granulites from the Kaithapalli area which lies NW of Chilka Lake, Odisha is reported. The area tectonically forms a northern part of Eastern Ghats belt. It occurs as small enclaves within the khondalite and pelitic granulite. The mineral assemblage includes spinel-sapphirine-garnet-cordierite-orthopyroxene-sillimanite-biotite-k-feldspar-plagioclase-quartz. Development of reaction textures and symplectites are common in the sapphirine-spinel granulites which have been used to describe reaction history. The relative X Mg values among various minerals are as follows: cordierite > biotite > sapphirine > orthopyroxene > garnet > spinel. The P-T evolution of these sapphirine-spinel granulites constrained through the pseudosection modelling in the NCKFMASH model system using PerpleX software indicate conditions of ultra-high temperature (UHT) metamorphism. The P-T estimates computed by isopleths define a retrograde trajectory with decompression of c.2.5 kbar from P-T max of c.10.5 kbar at c.950 oC. The sequence of reactions as deduced from the symplectite assemblages, together with pseudosection modelling, from the Kaithapalli area, offer greater opportunities for providing a better picture of petrological evolution of northern part of the Eastern Ghats Belt (EGB). © 2019, Geological Society of India