A promising RVO4:Eu3+,Li+@SiO2 (R = Gd,Y and Gd/Y) red‐emitting phosphor with improved luminescence (cd/m2) and colour purity for optical display applications

Red emission intensity was optimized in three stages, by investigating the effects of: (i) host composition (Gd, Y and Gd/Y), (ii) codoping Li⁺ as a sensitizer and, finally, (iii) with a SiO₂ shell coating as a protecting layer. Lanthanide vanadate powder phosphors were synthesized using a modified colloidal precipitation technique. The effects of SiO₂ coating on phosphor particles were characterized using scanning electron microscopy (SEM)‐EDAX, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and photoluminescence (PL) measurements. An improvement in the PL intensity on Li codoping was due to improved crystallinity, which led to higher oscillating strengths for the optical transitions, and also a lowering of the inversion symmetry of Eu³⁺ ions. Red emission intensity due to ⁵D₀ → ⁵D₂ transition of the phosphor Y_0.94VO₄:Eu³⁺_0.05,Li⁺_0.01 was enhanced by 22.28% compared with Y_0.95VO₄:Eu³⁺_0.05, and was further improved by 58.73% with SiO₂ coating. The luminescence intensity (I) and colour coordinates (x, y) of the optimized phosphor Y_0.94VO₄:Eu³⁺_0.05,Li⁺_0.01@SiO₂, where I = 13.07 cd/m² and (x = 0.6721, y = 0.3240), were compared with values for a commercial red phosphor (Y₂O₂S:Eu³⁺), where I = 27 cd/m² and (x = 0.6522, y = 0.3437). The measured colour coordinates are superior to those of the commercial red phosphor, and moreover, match well with standard NTSC values (x = 0.67, y = 0.33). Copyright © 2015 John Wiley & Sons, Ltd.     

Centromeric histone H3 protein: from basic study to plant breeding applications

Centromere is the defining unit of a chromosome where kinetochore complex assembles and facilitates chromosome segregation. Centromeres contain unique repetitive sequences and are enriched with transposons and retrotransposons. Although how centromere is determined is still not clearly understood, binding of a key protein, namely, the Centromeric Histone H3 (CENH3) to centromeric repetitive DNA sequences has been found to be critical for the specification of centromere. Hence, centromeres are said to be epigenetically specified by CENH3. Despite considerable variation in size and sequence, CENH3 protein shows significant conservation of structure and function. CENH3 disruption or overexpression shows severe defects in spindle fiber attachment and ultimately leads to embryo lethality. Basic studies on complementation of CENH3 in Arabidopsis thaliana have led to the development of a novel method of haploid production through selective elimination of one set of parental chromosomes in the zygote. These findings have also shed new light on selective loss of chromosomes in interspecific crosses of Hordeum vulgare × H. bulbosum. Here, we briefly review unique features of CENH3 and discuss the new plant breeding opportunities that have emerged from the study of CENH3.     

Crystal structure of a tripeptide containing aminocyclododecane carboxylic acid: a supramolecular twisted parallel β‐sheet in crystals

The crystal structure of a tripeptide Boc‐Leu‐Val‐Ac₁₂c‐OMe ( 1 ) is determined, which incorporates a bulky 1‐aminocyclododecane‐1‐carboxylic acid (Ac₁₂c) side chain. The peptide adopts a semi‐extended backbone conformation for Leu and Val residues, while the backbone torsion angles of the C^α,α‐dialkylated residue Ac₁₂c are in the helical region of the Ramachandran map. The molecular packing of 1 revealed a unique supramolecular twisted parallel β‐sheet coiling into a helical architecture in crystals, with the bulky hydrophobic Ac₁₂c side chains projecting outward the helical column. This arrangement resembles the packing of peptide helices in crystal structures. Although short oligopeptides often assemble as parallel or anti‐parallel β‐sheet in crystals, twisted or helical β‐sheet formation has been observed in a few examples of dipeptide crystal structures. Peptide 1 presents the first example of a tripeptide showing twisted β‐sheet assembly in crystals. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Orientational and rotational velocity correlation functions for water-hydrating B- and Z-DNA double helices

The molecular dynamics simulations reported earlier for the structure and dynamics of water molecules hydrating B- and Z-DNA double helices are analyzed for the orientational correlation functions and the proton rotational velocity autocorrelation functions. The spectra of the rotational velocity autocorrelation functions obtained from the simulation results are compared with the neutron inelastic scattering experiments on hydrated Na-DNA samples. The results predict a small frequency component associated with water molecules bound to the double helices that disappears for waters away from the double helix.     

Fructose diphosphate aldolase from Mycobacterium smegmatis. Purification and properties.

Fructose diphosphate aldolase has been purified to homogeneity from Mycobacterium smegmatis. Physicochemical studies showed that the enzyme is a tetramer of molecular weight 158,000. Mycobacterium smegmatis aldolase, though a bacterial enzyme, possesses properties similar to other class I aldolases. Inactivation of the enzyme by sodium borohydride in presence of dihydroxyacetone phosphate suggested the formation of a Schiff-base intermediate.     

Differentiation ex ovulo of Embryos and Plantlets in Stem Tissue Cultures of Tylophora indica

Tylophora indica callus tissue repeatedly subcultured every month on a series of different nutrient media in sequence regenerated roots, shoots and typical, bipolar embryos in vitro from unorganized callus parenchyma. The embryo-like structures developed from somatic cells grew into normal plantlets when isolated and cultured on appropriate milieu of nutrients and hormones bypassing the normal sexual method of reproduction. Likewise, free cells in suspension also passed through embryonic stages reminiscent of development from fertilized egg.     

Blockade of adrenergic responses by halogenated phenyl-2-halogenoethyl amines

The action of halogenated phenyl 2-halogenoethylamines on adrenergic α-receptor sites of the rat vas deferens was studied. The effect of halogen (Br) substituents in the phenyl nucleus resulted in the following differences in activity: para > meta - para > meta > ortho. All compounds possessed a short duration of action; recovery from adrenergic blockade was complete within 120 min. Exposure of tissues to phenoxybenzamine, after complete recovery from adrenergic blockade by the test compounds, did not alter the magnitude of initial blockade but sharply reduced the duration of action of phenoxybenzamine. These results are discussed in terms of a model which proposes at least 2 sites of action for 2-halogenoethylamines at the adrenergic α-receptors of the rat vas deferens.     

Theoretical studies on the behavior of carotid sinus baroreceptors

An approach to mathematical modeling of the baroreceptor that appears suitable for modeling mechanoreceptors in general is discussed. It differs from earlier works reported in the literature in the fact that it divides the baroreceptor into different functional components and attempts to describe mathematically the functioning of each component. The model consists of three first-order ordinary differential equations, one of which is linear; and there are ten free parameters. The ability of the model to fit different sets of experimental data with a single set of parameter values for a given class of inputs is demonstrated.     

Studies on tryptophan residues of Abrus agglutinin. Stopped-flow kinetics of modification and fluorescence-quenching studies.

The presence of two essential tryptophan residues/molecule was implicated in the binding site of Abrus agglutinin [Patanjali, Swamy, Anantharam, Khan & Surolia (1984) Biochem. J. 217, 773-781]. A detailed study of the stopped-flow kinetics of the oxidation of tryptophan residues revealed three classes of tryptophan residues in the native protein. A discrete reorganization of tryptophan residues revealed three classes of tryptophan residues in the native protein. A discrete reorganization of tryptophan residues into two phases was observed upon ligand binding. The heterogeneity of tryptophan exposure was substantiated by quenching studies with acrylamide, succinimide and Cs+. Our study revealed the microenvironment of tryptophan residues to be hydrophobic, and also the presence of acidic amino acid residues in the vicinity of surface-localized tryptophan residues.     

Hydration structure and dynamics of B- and Z-DNA in the presence of counterions via molecular dynamics simulations

Following our previous attempts at understanding the structural and dynamical properties of water and counterions hydrating nucleic acids, we have performed molecular dynamics simulations for B- and Z-DNA. In these simulations, the nucleic acids were held rigid. In the case of B-DNA, one turn of B-DNA double helix was considered in the presence of 1500 water molecules and 20 counterions (K⁺). The simulations were performed for 4.0 ps after equilibrating the system. For Z-DNA, we considered one turn of the double helix in the presence of 1851 water molecules and 24 counterions (K⁺). The simulations were carried out for 3.5 ps after equilibration. The average temperature of these simulations was ～ 360 K for Z-DNA and ～ 345 K for B-DNA. In these simulations the hydrogen atoms were explicitly taken into account. For both simulations, a fifth-order predictor-corrector was used for solving the translational equations of motion. The rotational motion of the water molecules was represented in terms of quaternion algebra and the rotational equations of motion were solved with a second-order quaternion method using a sixth-order predictor-corrector method. A time step of 0.5 · 10^?15 s was used in these simulations. The structural and the dynamical properties of water solvating the counterions, and the phosphate groups of the DNA, were computed to understand the hydration structure. Diffusion coefficients and velocity correlation functions were calculated for both ions and the water molecules. The velocity correlation functions for the ions exhibit a caged behavior. The dipole correlation functions for the water molecules indicate that the water molecules close to the helix retain the memory of their initial orientations for longer periods of time than those away from the helix. During the time period of our simulation (3–4 ps) the ion probability distributions show a well-defined pattern and suggest limited mobility for the ions, being close to the helix.