Amount Of Phosphate Groups Research Articles

Laboratory Adsorption Studies on Cadmium (II) by Nonwoven Chitosan/Phosphorylated Microcellulose Nanocomposite

The rapid growth of human population and global industrialization has resulted in the generation of larger amounts of wastewater containing various pollutants, among which toxic heavy metals. Adsorption is efficient for this purpose, but its application is limited by the high cost of adsorbent materials. Chitosan (CS) and phosphorylated microcellulose (PMC) have a high potential as low-cost and effective adsorbents for water remediation. Nonwoven CS/PMC nanocomposite fiber mats were produced by electrospinning with up to 50% by weight of PMC. The thermal, chemical, and morphological properties of the mats were studied. Batch adsorption trials were carried out using Cd2+ ions. Kinetics and isotherm models were tested against experimental results and the thermodynamic properties were calculated. Results showed that the pseudo-second order model best fitted experimental data and suggested chemisorption as the mechanism for Cd2+ removal. Langmuir isotherm best described equilibrium data reaching the maximum adsorption capacity of 283 mg/g at 60 °C. This high value was attributed mainly to the large amount of phosphate groups, which require less energy to capture the metal cations. Thermodynamic evaluation suggested that the adsorption is a spontaneous endothermic reaction. These results confirm that CS/PMC mats are easy to produce, and provide high adsorption capacity in simulated wastewater containing Cd2+. These laboratory-based adsorption experiments will assist in selecting/ranking of potential candidate matrices, and scale-up development of technologies for complex wastewater applications.

Microgels of Starch Phosphates for the Controlled Release of Biomacromolecules

Hydrogels on the basis of starch phosphates containing 2.1-3.8 mmol/g of phosphoric acid groups have been prepared by etherification of starch in an orthophosphoric acid-urea system. In in vitro experiments, the rate of starch phosphates degradation in a phosphate buffer in the absence and presence of а-amylase in the reaction mixture was studied. It was shown that phosphate starch is available for enzymatic hydrolysis; however, the rate of biodegradation was gradually reduced with increasing amounts of phosphate groups. The possibility of using microgels with average sizes 7.8-60.1 μm to create systems with interferon alpha-2b controlled release was demonstrated.

Effects of background anionic compounds on the activity of the hammerhead ribozyme in Mg(2+)-unsaturated solutions.

Cellular ribozymes exhibit catalytic activity in media containing large numbers of anionic compounds and macromolecules. In this study, the RNA cleavage activity of the hammerhead ribozyme induced by Mg(2+) was investigated using the solutions containing background nucleic acids, small phosphate and carboxylic acid compounds, and neutral polymers. Analysis of the substrate cleavage kinetics showed that the anionic compounds do not affect the ribozyme activity in Mg(2+)-saturated solutions and there is almost no effect of the anion-Mg(2+) complexes formed. On the other hand, the rate of substrate cleavage in Mg(2+)-unsaturated solutions was reduced under conditions of a high background of anionic compounds found in cells. The extent of the reduction was more with a greater net negative charge, caused by decreased amounts of Mg(2+) that could be used for the ribozyme reaction. It was remarkable that background DNA and RNA molecules having phosphodiester bonds reduced the cleavage rate as much as adenosine monophosphates having a charge of -2 when the effects of the same amount of phosphate groups were compared. Greater reductions in rates than those expected from the molecular charge were also observed in the background of fatty acids that form micelles. An addition of poly(ethylene glycol) to the solutions partially restored the ribozyme activity, suggesting a possible role of macromolecular crowding in counteracting the inhibitory effects of background anions on the ribozyme reaction. The results have biological and practical implications with respect to the effects of molecular environment on the efficiency of ion binding to RNA.

Chemical Characterization of Yellow and Orange Pollen <i>(Helianthus annuus) </i>and its Effect in the Growth of Hydroxyapatite

In this work orange pollen grains (Helianthus annuus) were immersed in a supersaturated ionic solution (similar to human extracellular fluid) during different times at 37 °C, atmospheric pressure and pH of 7.4. By Fourier transform infrared spectroscopy (FT-IR) we confirmed the presence of the functional groups carbonyl, amide I, amide II, carboxyl and phosphate in both samples. Nevertheless, yellow pollen owns a greater amount of phosphate groups than orange pollen. By scanning electron microscopy (SEM), differences in the morphology, shape and size of both samples were not observed. In orange pollen grains, amorphous agglomerates can be observed for periods smaller to 14 days and spherical structures formed by nanocrystals of laminar form were observed on their surface at 17 days. By energy dispersive spectroscopy (EDS) confirms the presence of calcium and phosphorous in the agglomerates with different Ca/P ratio and by X-ray diffraction (XRD) the hydroxyapatite (HAp) phase was verified.

Apatite-forming ability on titanium surface modified by hydrothermal treatment and ultraviolet irradiation

Titania coatings with various morphologies were formed on titanium surfaces by hydrothermal treatment using a dilute alkaline solution and evaluated in their hydroxyapatite (HA)-forming abilities in simulated body fluid (1.5SBF) under ultraviolet (UV) irradiation. The HA formation on the titania coating in 1.5SBF was enhanced by UV irradiation. The amount of phosphate groups adsorbed on the titania, after soaking in 1.5SBF for 24 h under UV irradiation, was estimated to be larger than that of calcium ions, whereas that of calcium ions on the titania, after soaking without UV irradiation, was larger than that of phosphate groups. It was suggested that the titania generated much basic Ti–OH groups at its surface by UV irradiation and subsequently adsorbed phosphate groups, such as H2PO4−, resulting in the formation of a new surface rich in the amount of the groups, which eventually enhanced the HA formation in 1.5SBF.

A new Phosphorylated Polysaccharide for Biomedical Applications: Generation of 3D Scaffolds with Osteogenic Activity and Coating of Titanium Oxide Surfaces

AbstractSummary:A new phosphorylated derivative of carboxymethylcellulose and amidic carboxymethylcellulose containing one phosphate group for each disaccharide unit was synthesized using sodium trimetaphospahte (STMP) as the phosphating agent. The new polysaccharide was characterized by infrared spectroscopy (FT‐IR) and the amount of phosphate groups was determined by elemental analysis. These modified polysaccharides were used both to prepare 3D scaffolds and functionalize titanium oxide surfaces with the aim to improve the osseointegration with the host tissue. The presence of phosphate groups modify the physical‐chemical properties of the hydrogels with respect to the native ones. The evaluation of the bioactivity of the phosphorylated carboxymethylcellulose hydrogels towards osteoblast‐like cells showed a significant increase in the osteocalcin production. The modified surfaces were chemically characterized by means of X‐ray photoelectron spectroscopy (XPS) and FT‐IR, whereas the surface topography was analysed by Atomic Force Measurements (AFM) measurements before and after the polysaccharide coating. In vitro biological tests using osteoblast‐like cells demonstrated that phosphorylated carboxymethylcellulose functionalized TiO2 surfaces promoted better cell adhesion and significantly enhanced their proliferation. These findings suggest that the phosphate polysaccharide both as a 3D scaffold and as a surface coating promotes osteoblast growth potentially improving the biomaterial osseointegration rate.

Isolation of new nonconditional Saccharomyces cerevisiae mutants defective in asparagine-linked glycosylation.

We describe the isolation and partial characterization of Saccharomyces cerevisiae nonconditional mutants that show defects in N-glycosylation of proteins. The selection method is based on the reduction of affinity for the ion exchanger QAE-Sephadex as a consequence of the decrease in the negative charge of the cell surface. This characteristic reflects a decrease in the incorporation of mannosylphosphate units into the N-linked oligosaccharides of the mannoproteins. The mutants exhibit low affinity for the basic dye alcian blue and for that reason we have called them Idb (low dye binding) mutants. Eight of the complementation groups seem to be new as shown by complementation studies with previously isolated mutants of similar phenotype. Four of the groups showed a significant reduction in the number and/or size of the N-linked oligosaccharides attached to secreted invertase. We have analyzed the N-linked oligosaccharides of Idb1 and Idb2, the mutants that show the most drastic reduction in the affinity for the alcian blue dye. In both cases, the purified endo H-released oligosaccharides from the mannoproteins lacked detectable amounts of phosphate groups as shown by ion exchange chromatography and the 1H NMR spectra. In addition, Ibd1 synthesizes a truncated and unbranched outer chain lacking any alpha (1,2) linked mannoses attached to the alpha (1,6) linear backbone.