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

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

Electrohydrodynamic Assembly of Ambient Ion-Derived Nanoparticles to Nanosheets at Liquid Surfaces

We describe an ambient ion-based method to create free-standing metal nanosheets, which in turn are composed of nanoparticles of the corresponding metal. These nanoparticle-nanosheets (NP-NSs) were formed by the electrospray deposition (ESD) of metal ions on a liquid–air interface leading to nanoparticles that self-organize under the influence of electrohydrodynamic flows, driven by the electric field induced by the applied potential. Such a two-dimensional organization of noble metals is similar to the assembly of molecules at liquid–air interface and has the possibility of creating a category of new materials useful for diverse applications. Enhanced catalytic activity of the formed NP-NSs for Suzuki–Miyaura coupling reaction was demonstrated, which was attributed to their large surface-to-volume ratios

Electrohydrodynamic Assembly of Ambient Ion-Derived Nanoparticles to Nanosheets at Liquid Surfaces

We describe an ambient ion-based method to create free-standing metal nanosheets, which in turn are composed of nanoparticles of the corresponding metal. These nanoparticle-nanosheets (NP-NSs) were formed by the electrospray deposition (ESD) of metal ions on a liquid–air interface leading to nanoparticles that self-organize under the influence of electrohydrodynamic flows, driven by the electric field induced by the applied potential. Such a two-dimensional organization of noble metals is similar to the assembly of molecules at liquid–air interface and has the possibility of creating a category of new materials useful for diverse applications. Enhanced catalytic activity of the formed NP-NSs for Suzuki–Miyaura coupling reaction was demonstrated, which was attributed to their large surface-to-volume ratios

Electrohydrodynamic Assembly of Ambient Ion-Derived Nanoparticles to Nanosheets at Liquid Surfaces

We describe an ambient ion-based method to create free-standing metal nanosheets, which in turn are composed of nanoparticles of the corresponding metal. These nanoparticle-nanosheets (NP-NSs) were formed by the electrospray deposition (ESD) of metal ions on a liquid–air interface leading to nanoparticles that self-organize under the influence of electrohydrodynamic flows, driven by the electric field induced by the applied potential. Such a two-dimensional organization of noble metals is similar to the assembly of molecules at liquid–air interface and has the possibility of creating a category of new materials useful for diverse applications. Enhanced catalytic activity of the formed NP-NSs for Suzuki–Miyaura coupling reaction was demonstrated, which was attributed to their large surface-to-volume ratios