Study of trivalent samarium ion embedded lithium‐based borate glass for high‐density optical memory devices

Sm³⁺ ions doped strontium lithium lead borate glasses (SLLB:Sm) were prepared using a conventional melt‐quenching technique. The glasses were analyzed using X‐ray diffractometry and Fourier transform infrared spectroscopy, optical absorption, fluorescence spectral analysis, and fluorescence lifetime decay. The Judd–Ofelt (J–O) parameters and radiative parameters of the SLLB:Sm10 glass (1.0 mol% Sm³⁺ ion‐doped glass) were calculated using J–O theory. From the emission spectra, among all the synthesized glass, SLLB:Sm10 glass had the highest emission intensity for ⁴G_5/2→⁶H_11/2 transition (610 nm). Emission parameters, such as stimulated emission cross‐section and optical gain bandwidth, were calculated. For all concentrations of Sm³⁺ ions, the decay profile showed an exponential nature and decreased when the Sm³⁺ ion concentration was increased due to a concentration quenching effect. This result suggests that the synthesized SLLB:Sm10 glass could be used for application in high‐density optical memory devices.     

Synthesis, crystal structure and vibrational spectroscopy of a novel mixed ligands Ni(II) pentaborate: [Ni(C4H10N2)(C2H8N2)2][B5O6(OH)4]2

A novel organic-inorganic hybrid pentaborate [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂][B₅O₆(OH)₄]₂ has been synthesized by hydrothermal reaction and characterized by FT-IR, Raman spectroscopy, elemental analyses and DTA-TGA. Its crystal structure was determined from single crystal X-ray diffraction. The structure consists of isolated polyborate anion [B₅O₆(OH)₄]⁻ and nickel complex cation of [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂]²⁺, in which the two kinds of ligands come from the decomposition of triethylenetriamine material. The [B₅O₆(OH)₄]⁻ units are connected to one another through hydrogen bonds, forming a three-dimensional framework with large channel along the a and c axes, in which the templating [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂]²⁺ cations are located. The assignments of the record FT-IR absorption frequencies and Raman shifts were given.     

Isolation of active ribulose 1,5-bisphosphate carboxylase from glanded cotton (G. hirsutum)

Ribulose, 1,5-bisphosphate carboxylase has been isolated from leaves of glanded cotton, (Gossypium hirsutum L. cv. TM1), by techniques described. A yield exceeding 4.5 mg enzyme per gram leaf tissue has been obtained by utilizing a sodium homogenizing buffer without the addition of any reducing agent. Sodium dodecylsulfate gel electrophoresis of the enzyme shows the fraction to be relatively free of contaminants. Enzymic assays of the isolate give a specific activity of 1.1 μmol CO₂ fixed (min-mg protein)^?1 at 30°C.     

The composition and structure of lithium tetrakis(pentafluorophenyl)borate diethyletherate

Treatment of LiC₆F₅ with B(C₆F₅)₃ in equal volumes of light petroleum and diethyl ether at low temperature followed by slow warming to room temperature precipitates a microcrystalline solid which dries under vacuum to a material with the composition [Li(OEt₂)₃][B(C₆F₅)₄]. Crystallization from diethyl ether yields solvent dependent [Li(OEt₂)₄][B(C₆F₅)₄], which has been crystallographically characterised.     

Synthesis, structures and luminescent behaviour of tridentate salicylaldiminato-type borate complexes

Treatment of the ligands 3,5-tBu₂-2-(OH)C₆H₂CHNR [R = 2-(CO₂H)C₆H₄ (1a) and 2-(CO₂H)C₁₀H₆ (1b)] with trimethylborate, B(OMe)₃, in toluene yields, after work-up, the yellow crystalline complexes {[3,5-tBu₂-2-(O)C₆H₂CHNR]B(OMe)} [R = 2-(CO₂)C₆H₄ (2a) and 2-(CO₂)C₁₀H₆ (2b)], respectively. Further treatment of these complexes with trifluoromethanesulfonic (triflic) acid, CF₃SO₃H, followed by recrystallisation from tetrahydrofuran (thf) afforded the triflate salts [{3,5-tBu₂-2-(O)C₆H₂CHNR}B(thf)][CF₃SO₃] [R = 2-(CO₂)C₆H₄ (3a) and 2-(CO₂)C₁₀H₆ (3b)]. An electroluminescent device was constructed using 2a, which produced orange-green light with broad emission spectra (maximum brightness of 5 cd/m² being observed at 13 V). Compounds 1a and 2b·2MeCN have been characterised by single crystal X-ray structure determinations.     

l-Galactose replaces l-fucose in the pectic polysaccharide rhamnogalacturonan II synthesized by the l-fucose-deficient mur1 Arabidopsis mutant

Arabidopsis thaliana mur1 is a dwarf mutant with altered cell-wall properties, in which l-fucose is partially replaced by l-galactose in the xyloglucan and glycoproteins. We found that the mur1 mutation also affects the primary structure of the pectic polysaccharide rhamnogalacturonan II (RG-II). In mur1 RG-II a non-reducing terminal 2-O-methyl l-galactosyl residue and a 3,4-linked l-galactosyl residue replace the non-reducing terminal 2-O-methyl l-fucosyl residue and the 3,4-linked l-fucosyl residue, respectively, that are present in wild-type RG-II. Furthermore, we found that a terminal non-reducing l-galactosyl residue, rather than the previously reported d-galactosyl residue, is present on the 2-O-methyl xylose-containing side chain of RG-II in both wild type and mur1 plants. Approximately 95% of the RG-II from wild type and mur1 plants is solubilized as a high-molecular-weight (>100 kDa) complex, by treating walls with aqueous potassium phosphate. The molecular mass of RG-II in this complex was reduced to 5–10 kDa by treatment with endopolygalacturonase, providing additional evidence that RG-II is covalently linked to homogalacturonan. The results of this study provide additional information on the structure of RG-II and the role of this pectic polysaccharide in the plant cell wall.Abbreviations AIR Alcohol-insoluble residue - d-Gal d-Galactosyl - EPG Endopolygalacturonase - ESI–MS Electrospray ionization mass spectrometry - GC–MS Gas chromatography–mass spectrometry - ¹H-NMR Proton nuclear magnetic resonance spectroscopy - l-Fuc l-Fucosyl - l-Gal l-Galactosyl - 2-O-MeFuc 2-O-Methyl l-fucosyl - 2-O-MeGal 2-O-Methyl l-galactosyl - 2-O-MeXyl 2-O-Methyl d-xylosyl - MWCO Molecular weight cut-off - RG-II Rhamnogalacturonan II - ppm Parts per million - RI Refractive index - SEC Size-exclusion chromatography - TFA Trifluoroacetic acid - WT Wild type     

Boric acid complexes with organic biomolecules: Mono-chelate complexes with salicylic and glucuronic acids

Two mono-chelate borate complexes, lithium mono-salicylatoborate and sodium mono-glucuronatoborate, are reported for the first time. The complexes were isolated from aqueous solutions and characterized by FTIR (Fourier Transform Infrared) and ¹³C MAS (Magic Angle Spinning) NMR techniques. Thermal stabilities of the complexes were examined by recording their TGA (Thermogravimetric Analysis) curves. Lithium mono-salicylatoborate, Li[B(Sal)(OH)₂], was isolated in crystal form and presented as a novel hybrid metal-organic framework possessing zeolitic structure. X-ray analysis revealed an original crystal structure constructed with solvate-free lithium ions adopting two different types of coordination polyhedra, corner-sharing LiO₄ (tetrahedral) and LiO₅ (distorted square pyramidal), in the same framework.     

High boron-induced ubiquitination regulates vacuolar sorting of the BOR1 borate transporter in Arabidopsis thaliana

Boron homeostasis is important for plants, as boron is essential but is toxic in excess. Under high boron conditions, the Arabidopsis thaliana borate transporter BOR1 is trafficked from the plasma membrane (PM) to the vacuole via the endocytic pathway for degradation to avoid excess boron transport. Here, we show that boron-induced ubiquitination is required for vacuolar sorting of BOR1. We found that a substitution of lysine 590 with alanine (K590A) in BOR1 blocked degradation. BOR1 was mono- or diubiquitinated within several minutes after applying a high concentration of boron, whereas the K590A mutant was not. The K590A mutation abolished vacuolar transport of BOR1 but did not apparently affect polar localization to the inner PM domains. Furthermore, brefeldin A and wortmannin treatment suggested that Lys-590 is required for BOR1 translocation from an early endosomal compartment to multivesicular bodies. Our results show that boron-induced ubiquitination of BOR1 is not required for endocytosis from the PM but is crucial for the sorting of internalized BOR1 to multivesicular bodies for subsequent degradation in vacuoles.     

Comparative RP-HPLC for rapid identification of glycopeptides and application in off-line LC-MALDI-MS analysis

Despite the increasing attention being paid to the functions of glycoproteins, their structural analysis is still difficult and hinders functional investigations. Structural analysis of post-translationally modified proteins is thought to be achieved using methods frequently utilized in proteomics research; however, the same methods cannot be used for glycosylated proteins. One of the difficulties associated with the physiochemical properties of glycopeptides and peptides is that the detection of the former is considerably more difficult, because of the existence of glycoforms that increase molecular weight and reduces quantities of individual species. Thus, difficulties are often faced in finding glycopeptide(s) by using MS when analyzing peaks (or fractions) obtained after proteolytic digestion and HPLC. One simple yet difficult solution to this problem would be to develop a purification method that provides better resolution. Our intention has been to address this issue by using a combination of conventional methods. We found that a method consisting of a combination of rough fractionation using a reverse-phase cartridge column under acidic conditions and comparative RP-HPLC, where the two chromatograms obtained using phosphate and borate buffers under basic conditions were compared, is effective for MS-based structural analysis. The applicability of the method in glycoprotein analysis was examined using various samples including ribonuclease B (RNase B), IgG1, ovalbumin (OVA), and asialo fetuin (ASF). The results suggest that the method is useful in the analysis of glycoproteins.     

Molecular Modelling of the Mechanism of Action of Borate Retarders on Hydrating Cements at High Temperature

Abstract

We consider the class of borate additives in an attempt to understand, on the basis of molecular modelling techniques, why they are effective high temperature cement setting retarder aids. Borates are known to act as cement retarders under ambient conditions, for which the Billingham-Coveney clock reaction scheme [1] based on a gel → crystalline ettringite transformation provides the basic model. Under conditions of high temperature (above ca. 80°C) ettringite is known to be unstable, so that a modification to this mechanism is then required. However, conceptually (and mathematically) the kinetic scheme remains unchanged: we are concerned with a gel → crystalline silicate transition, which can be inhibited by suitable retarders. Thus the proposed mechanism for the high temperature retardation of hydrating cements by borates is that the latter prevent the growth of polymeric or crystalline calcium silicate hydrates such as tobermorite from the initially formed C ? S ? H gel.

The mechanism which we propose in this paper, which is based on chemisorption of borate species, explains some experimentally observed phenomena relating to the retarding action of both monomeric and polymeric borates in solution. On the basis of this work, we are able to predict vibrational frequencies for the cyclic borosilicate species which is formed, observation of which would confirm the validity of the mechanism proposed here. We can also use our work to explain the effectiveness of different borates. We conclude by suggesting a novel boronate retarder which might be expected to be more potent than those currently in use.