A Peptide Core Motif for Binding to Heterotrimeric G Protein α Subunits

Recently, in vitro selection using mRNA display was used to identify a novel peptide sequence that binds with high affinity to G{alpha}i1. The peptide was minimized to a 9-residue sequence (R6A-1) that retains high affinity and specificity for the GDP-bound state of G{alpha}i1 and acts as a guanine nucleotide dissociation inhibitor (GDI). Here we demonstrate that the R6A-1 peptide interacts with G{alpha} subunits representing all four G protein classes, acting as a core motif for G{alpha} interaction. This contrasts with the consensus G protein regulatory(GPR) sequence, a 28-mer peptide GDI derived from the GoLoco (G{alpha}i/0-Loco interaction)/GPR motif that shares no homology with R6A-1 and binds only to G{alpha}i1-3 in this assay. Binding of R6A-1 is generally specific to the GDP-bound state of the G{alpha} subunits and excludes association with G{beta}{gamma}. R6A-G{alpha}i1 complexes are resistant to trypsin digestion and exhibit distinct stability in the presence of Mg2+, suggesting that the R6A and GPR peptides exert their activities using different mechanisms. Studies using G{alpha}i1/G{alpha}s chimeras identify two regions of G{alpha}i1 (residues 1–35 and 57–88) as determinants for strong R6A-Gi{alpha}1 interaction. Residues flanking the R6A-1 peptide confer unique binding properties, indicating that the core motif could be used as a starting point for the development of peptides exhibiting novel activities and/or specificity for particular G protein subclasses or nucleotide-bound states

Investigation of Intrinsic Stress and Transport Properties of Fe/P-Si (001) Schottky Heterojunction

We present a comprehensive study on the growth morphology, the electrical and magnetic transport properties of thin iron (Fe) film on p-Si(100) substrate. The structural analysis revealed the growth of an amorphous Fe film, with low crystalline ordering and granular structure. The resistivity of the film was observed to deviate from the usual metallic behavior at lower temperature revealing a tunneling type conductance. This was also reflected in the magnetoresistance measurement of the film. The film show high positive (negative) magnetoresistance at all temperatures (below 10 K) on application of out-of-plane (in-plane) magnetic field. The current-voltage (I-V) measurement of Fe/p-Si Schottky heterojunction exhibits good rectifying property. The ideality factor (n) and Schottky barrier height (fb) of the device, at room temperature, were obtained from fitting the I-V curves. The carrier concentration of the semiconductor substrate was evaluated from the capacitance-voltage (C-V) measurements. From the measurements large deviation from the ideal value of the diode parameters was observed. All the results thus obtained show a strong correlation between the stress and the transport measurements

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Partition function congruences: Some flowers and seeds from ‘Ramanujan's garden’

AbstractThe discovery of some partition function congruences by Ramanujan, and subsequent research motivated by these congruences as well as some of his questions and conjectures, have brought forth a beautiful bower in ‘Ramanujan's Garden’.In this short expository article, starting from Ramanujan's pioneering work in this area, we have some glimpses of contributions of many of the later researchers like Atkin, Watson, Newman, Winquist, Zuckerman, Dyson, Andrews, Garvan, Schinzel, Wirsing, Nicolas, Ruzsa, Sárközy, Serre, Berndt and Ono. While we dwell mainly on the question of parity of p(n) and related topics, we try to mention other important achievements in the area

Regeneration of plantlets through somatic embryogenesis from root derived calli of Hibiscus sabdariffa L. (Roselle) and assessment of genetic stability by flow cytometry and ISSR analysis.

Induction of somatic embryogenesis and complete plantlet regeneration from callus culture of Hibiscus sabdariffa L. var. HS4288 has been made. Leaf and root explants were cultured on Murashige and Skoog (MS) and Driver-Kuniyuki Walnut (DKW) basal media supplemented with different concentrations of synthetic auxins and cytokinins. Root explants on DKW medium supplemented with 2.26μM 2, 4-Dichlorophenoxyacetic acid (2, 4-D) and 4.65μM kinetin (KIN) induced highest percentage (70%) of embryogenic calli. Average number of globular embryos per root derived callus produced within 6 weeks of culture initiation on MS media with different plant growth regulators (PGRs) ranged from 2.27±0.12 to 8.80±0.17 and that of cotyledonary embryos ranged from 0.00 to 2.53±0.20. On DKW medium comparatively more globular embryos (2.70±0.15 to 14.53±0.23) and cotyledonary embryos (0.00 to 8.90±0.17) were produced than that of MS medium. Regeneration of complete plantlets was highest (76.67%) when embryogenic calli with mature somatic embryos were grown on DKW medium containing 2.32μM KIN and 2.22μM 6-Benzyladenine (BA). Plants were primarily hardened in humidity, temperature and light controlled chamber and finally in a greenhouse showed 70% survival ability. Different stages of somatic embryogenesis process in the root derived embryogenic calli were elaborated in detail by morphological, histological and SEM study. The data were statistically analyzed by Duncan Multiple range test (p ≤ 0.05) and Principal component analysis (PCA). Flow cytometry and Inter-simple sequence repeats (ISSR) marker analysis confirmed that there was no genetic variation within the regenerated plants

Tuning the Size of CsPbBr₃ Nanocrystals: All at One Constant Temperature

For varying the size of perovskite nanocrystals, variation in the reaction temperature and tuning the ligand chain lengths are established as the key parameters for high-temperature solution-processed synthesis. These also require sharp cooling for obtaining desired dimensions and optical stability. In contrast, using preformed alkylammonium bromide salt as the precise dimension-controlling reagent, wide window size tunable CsPbBr₃ nanocrystals were reported without varying the reaction temperature or changing the ligands. The size tunability even with ∼1 nm step growth regimes was achieved as a function of only the concentration of added alkylammonium bromide salt. Not only the cube shape but also the width varied in the sheet structures. Because these nanostructures lose their optical stability and crystal phase on prolonged annealing, stabilizing these in high-temperature synthesis for all-inorganic lead halide perovskites is important and remains challenging. In this aspect, this method proved to be more facile because it does not require sharp cooling, and the nanocrystals retained their phase and optical properties even upon prolonged annealing

Layered Perovskites L₂(Pb_1–<i>x</i>Mn_<i>x</i>)Cl₄ to Mn-Doped CsPbCl₃ Perovskite Platelets

Doped perovskite nanocrystals have recently emerged as a new class of energy materials for solar concentrators and solid-state lighting device applications. Among these, doping Mn­(II) in high band gap CsPbCl₃ perovskite host nanostructures has been extensively studied. However, going beyond their optical emissions, herein, the impact of dopant ions on tuning the doped platelet dimensions and retaining the monodispersity is reported. These were performed by designing appropriate compositions of layered perovskites, L₂(Pb_1–<i>x</i>Mn_<i>x</i>)­Cl₄, which on thermal treatment in the presence of Cs­(I) ions transformed to Mn-doped CsPbCl₃ platelets. Correlating the amount of Mn present in layered perovskites and retained in doped platelets, the role of Mn for the conversion of layered to doped perovskites was established. These doped platelets showed dominated Mn d–d emission and also Mn concentration-dependent emission tuning. Even though several reports of Mn-doped CsPbCl₃ have been reported, these findings add new fundamental insight into the design of dimension-tunable doped perovskites from layered perovskites