Effects Of Different Chemical Modifications Research Articles

Investigations on structure and properties of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforced by diss fibers: Effect of various surface treatments

The paper reports some experimental results on the effect of different chemical modifications of Diss fibers on the properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biocomposites involving alkaline, combined alkaline/peroxide and combined alkaline/silane treatments. The biocomposite samples loaded at 20 wt% were prepared by melt compounding. Scanning Electron Microscopy (SEM) showed a better fiber-matrix interaction between Diss fiber and matrix after surface fiber treatment. Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD) results indicated an increase in crystallinity index of the biocomposites. In addition, the incorporation of Diss fibers treated with alkali-silane resulted in an improvement in Heat Deflection Temperature (HDT) and shore D hardness from 141.1 °C and 75.1–145.7°C and 86.2, respectively, in comparison with the neat matrix. This also agreed with the flexural properties results, which showed a significant increase in flexural modulus by almost 30 % compared to the neat PHBV. The same trend was observed for water absorption. Overall, combined alkali-silane treatment was found to be most efficient surface treatment method to develop strong interfacial adhesion between PHBV and Diss fiber, increasing the scope of application in manufacturing of light weight green composites.

Preparation, Structural Analysis and Antioxidant Activity of Polysaccharides and Their Derivatives from Pueraria lobata.

Pueraria lobata polysaccharides (PLPs) were obtained by hot water extraction using Pueraria lobata as raw material. Structural analysis revealed that PLPs may have a repetitive backbone units of →4) -α-D-Glcp (1→4-α-D-Glcp (1→. Phosphorylated Pueraria lobata polysaccharides (P-PLPs), carboxymethylated Pueraria lobata polysaccharides (CM-PLPs) and acetylated Pueraria lobata polysaccharides (Ac-PLPs) were obtained by chemical modifications of PLPs, respectively. The physicochemical properties and antioxidant activities of these four Pueraria lobata polysaccharides were studied in comparison. In particular, the clearance rate of P-PLPs exceeded 80 %, and was expected to achieve the same effect as Vc . The results showed that the effects of different chemical modifications on the antioxidant activity of PLPs varied greatly.

Effects of different chemical modifications on the structure and biological activities of polysaccharides from Orchis chusua D. Don.

In this study, an enzyme-assisted extraction method was used to extract Orchis chusua D. Don (Salep) polysaccharide (SP), which was then modified by sulfation, acetylation, phosphorylation, and carboxymethylation to obtain modified polysaccharides. Furthermore, their degree of substitution, chemical composition, and molecular weight were evaluated. The primary structural features were characterized by UV spectra, FT-IR spectra, Congo-red test, and scanning electron microscope. The phosphorylated polysaccharide (SP-P) was demonstrated the highest scavenging ability on hydroxyl radical and growth-promoting activity on Lactobacillus Bulgaricus. The carboxymethylated polysaccharide (SP-C) was exhibited the strongest DPPH and ABTS radical scavenging effects. The acetylated polysaccharide (SP-A) displayed the best proliferation effects on Bifidobacterium adolescentis, whereas the sulfated polysaccharide (SP-S) maintained moderately stable antioxidant and probiotic ability. These findings indicate that the modified polysaccharides had their potential significance as new antioxidants and probiotics for the food industry. PRACTICAL APPLICATION: This article provides a new source for the development of polysaccharide derivatives as new antioxidants and probiotics for the food industry.

Effect of alkalinization-bleaching and acid hydrolysis treatment stalk sweet sorghum waste on compatibilities in polypropylene matrix

In this study, the effect of different chemical modifications of stalk sweet sorghum waste on compatibilities in polypropylene matrix has been discussed. Chemical treatments include alkalization-bleaching and alkalization-bleaching-acid hydrolysis treatments. The treatment was objective to improve the surface properties of the sorghum fibre and compatibilities in synthetic polymer matrix. Evaluation of the effect of different chemical modifications was measured with field-emission scanning electron microscope (FE-SEM) and tensile properties. The results showed that the compatibility and tensile strength of composite fibre alkalinization-bleaching treatment were better than untreated composites.

Effects of different chemical modifications on the antibacterial activities of polysaccharides sequentially extracted from peony seed dreg

The peony seed dreg polysaccharide (PSDPs) fractions and their modified derivatives were examined for their antibacterial potential. PSDPs along with their derivatives exhibited appreciable antibacterial activity against both Gram-positive (B. subtilis and S. aureus) as well as Gram-negative (E. coli and S. typhimurium) bacteria. Among the four polysaccharide fractions, HBSS possessed the greatest antibacterial activity with an inhibition zone of 13.6 mm against S. typhimurium, minimal inhibitory concentration of 0.12% against S. typhimurium and maximum bacterial growth inhibition. For the modified derivatives, the sulfated modified fraction (S-HBSS) exhibited the maximum antibacterial activity with inhibition zone of 15.4 mm and minimal inhibitory concentration of 0.08% against S. typhimurium, followed by carboxymethylated and phosphorylated derivatives. Out of the four tested bacteria, S. typhimurium was observed as the most sensitive strain which was inhibited most effectively by all the polysaccharide fractions. Overall, our findings clearly indicated that the selected polysaccharide fractions can be used as food ingredients with potential natural antibacterial prospective.

Effects of different chemical modifications on the antioxidant activities of polysaccharides sequentially extracted from peony seed dreg

Four types of sequentially extracted peony seed dreg polysaccharides (PSDPs) fractions were modified through sulfation, phosphorylation and carboxymethylation and studied for their in vitro antioxidant characteristics. The modified derivatives showed decreased sugar and protein content, while uronic acid content was elevated as compared to native (un-modified) polysaccharides. Further, modified derivatives shared the similar maximum absorption peaks indicating their homogeneous nature. The Fourier transform infrared (FTIR) spectra of sulfated, carboxymethylated and phosphorylated derivatives showed that hydroxyl groups were converted to OS, COO and POH bonds, respectively. The sulfated polysaccharides (S-PSDPs) displayed the highest reducing ability [S-CASS (1.854)], DPPH radical scavenging ability [S-CASS (95.07%)] and ABTS radical scavenging activity [S-CASS (99.85%)]. The phosphorylated polysaccharides (P-PSDPs) exhibited maximum hydroxyl radical scavenging activity [P-DASS (92.61%)] and ferrous ion chelating ability (99.94% for all the fractions). The carboxymethylated polysaccharides (C-PSDPs) maintained moderately stable antioxidant ability. Overall, the four different PSDPs modified by the same chemical method also resulted into different chemical composition, characteristic absorption peaks and antioxidant attributes. We conclude that the different modifications of the polysaccharide fractions had their own potential significance as new antioxidants for food industry and human health.

A Small Molecule Inhibitor of Bruton's Tyrosine Kinase Involved in B-Cell Signaling.

Protein kinases are fundamental within almost all cellular signal transduction networks. Among these, Bruton’s tyrosine kinase (Btk), which belongs to the Tec family of proteins, plays an imperative part in B-cell signaling. Owing to its role, Btk has been established as an important therapeutic target for a vast range of disorders related to B-cell development and function, such as the X-linked agammaglobulinemia, various B-cell malignancies, inflammation, and autoimmune diseases. Herein, using computer-based screening of a library of 20 million small molecules, we identified a small molecule capable of directly binding the Btk kinase domain. On the basis of this hit compound, we conducted a focused structure-similarity search to explore the effect of different chemical modifications on binding toward Btk. This search identified the molecule N2,N6-bis(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-9H-purine-2,6-diamine as a potent inhibitor of Btk. The latter small molecule binds Btk with a dissociation constant of 250 nM and inhibits Btk activity both in vitro and in-cell.

Mismatch discrimination in fluorescent in situ hybridization using different types of nucleic acids

In the past few years, several researchers have focused their attention on nucleic acid mimics due to the increasing necessity of developing a more robust recognition of DNA or RNA sequences. Fluorescence in situ hybridization (FISH) is an example of a method where the use of these novel nucleic acid monomers might be crucial to the success of the analysis. To achieve the expected accuracy in detection, FISH probes should have high binding affinity towards their complementary strands and discriminate effectively the noncomplementary strands. In this study, we investigate the effect of different chemical modifications in fluorescent probes on their ability to successfully detect the complementary target and discriminate the mismatched base pairs by FISH. To our knowledge, this paper presents the first study where this analysis is performed with different types of FISH probes directly in biological targets, Helicobacter pylori and Helicobacter acinonychis. This is also the first study where unlocked nucleic acids (UNA) were used as chemistry modification in oligonucleotides for FISH methodologies. The effectiveness in detecting the specific target and in mismatch discrimination appears to be improved using locked nucleic acids (LNA)/2'-O-methyl RNA (2'OMe) or peptide nucleic acid (PNA) in comparison to LNA/DNA, LNA/UNA, or DNA probes. Further, the use of LNA modifications together with 2'OMe monomers allowed the use of shorter fluorescent probes and increased the range of hybridization temperatures at which FISH would work.

Carbon Nanotubes Composites: Processing, Grafting and Mechanical and Thermal Properties

Carbon nanotubes represent one of the most important materials in nanoscience and nanotechnology today. The exceptional properties that these materials possess open new fields in science and engineering. Additionally, the chemistryassociated to these materi- als starts to play an important role, inasmuch, new moieties insert by different chemical routes, inside and outside of carbon nanotubes surfaces, have shown able to modify their structure and properties. To this date, new properties have been found in chemically-modified nanotubes and diverse potential applications are suggested for these materials. One of the most frequent applications for these carbon ma- terials is their inclusion as reinforcement in polymer matrices, due to the amazing structural, mechanical, electrical, chemical and thermal properties that carbon nanotubes possess, suggesting that these materials are ideal to produce new polymer nanocomposites. In this con- text, carbon nanotube nanocomposites have been developed by numerous research groups around the world aiming to produce new novel strong and light composite materials. Also, electrical conductivity and thermal properties have been studied for this kind of nanocompo- sites. However, new challenges to create a new age of multifunctional composite materials with these nanometric forms arise and, there- fore, the study of new properties in these nanocomposites has increased significantly in the last few years. In this review we discuss a range of methods to properly utilize nanotubes in poymer-based composites, from the solubility behavior of carbon nanotubes, the proc- essing methods to develop carbon nanotube polymer composites, interactions produced between carbon nanotubes and polymer grafted, to the most recent results on the mechanical and thermal properties of carbon nanotubes polymer composites, synthesized with different types of carbon nanotubes. In addition, we discuss the effect of different chemical modifications on nanotubes, with special focus on those developed to improve the compatibility between these nanostructures and engineering polymers, as well as their effect on the final composites properties. The significance of understanding, enhancing and controlling the behavior at the interface between nanotubes and polymer matrices towards the development of novel multifunctional applications with these composites, is also discussed in detail.

Preparation and evaluation of orange peel cellulose adsorbents for effective removal of cadmium, zinc, cobalt and nickel

Abstract The preparation of chemically modified orange peel cellulose adsorbents and its biosorption behaviors of Co(II), Ni(II), Zn(II) and Cd(II) have been studied. Effects of different chemical modifications on the adsorbent properties including different alkalis saponification (NaOH, NH 4 OH, and Ca(OH) 2 ) and different acids (C 6 H 6 O 7 ·H 2 O, H 2 C 2 O 4 , and H 3 PO 4 ) modification after saponification with NaOH were investigated. The FT-IR spectra showed that there are different functional groups in adsorbents, which are able to react with metal ions in aqueous solution. The maximum adsorption capacities of Ni(II), Co(II), Zn(II) and Cd(II) for SPA, SPA, SCA and SOA were obtained as 1.28, 1.23, 1.21 and 1.13 mol/kg and have increased by 95, 178, 60 and 130% compared to raw orange peel, respectively. Effects of initial pH, initial metal ions concentrations, shaking time and solid/liquid ratio on metal ions biosorption were also investigated. Biosorption equilibriums were rapidly established in about 60 min and the adsorption kinetics followed the Lagergren first-order kinetics model. The Langmuir and Freundlich adsorption isotherms models fitted the experimental data best with regression coefficient R 2 > 0.95 for all the metal ions. Elution efficiencies with different concentrations of HCl were evaluated.

Study on the preparation of orange peel cellulose adsorbents and biosorption of Cd 2+ from aqueous solution

In this paper, orange peel modified with different chemical reagents as biosorbents were used to remove cadmium ion from aqueous solution. Effects of different chemical modifications on the biosorbent properties including washing, alkali saponification, cross-linking temperature and concentration of cross-linking reagent were investigated. Meanwhile, influence of pH of solution, initial cadmium concentration, shaking time and solid/liquid ratio on the removed of Cd(II) by different chemically modified biosorbents were studied. It can be concluded that cadmium ion could be removed by 0.6SCA 80 (orange peel modified with 0.6 mol L −1 citric acid under 80 °C after alkali saponification) biosorbent effective and quick. We obtained a series of biosorbents with the order of cadmium: 0.6SCA 80 > SOP > CA2 > CA1 > PA1 > PA2 > OP. For 0.6SCA 80, the maximum capacity of cadmium was 0.90 mol kg −1, the optimum pH value was 6, the reaction balance was established after shaking 120 min and the optimum solid/liquid ratio was 4.3 g L −1. The desorption rate of cadmium was 94% with 0.15 mol L −1 HCl solution. A comparison of different isotherm models revealed that the Langmuir isotherm model is fitted the experimental data best. The biosorption follows the Lagergren first-order kinetics model.

Effects of different chemical modifications on peat humic acid and their bearing on some agrobiological characteristics of soils

Abstract Twelve preparations from peat humic acid were obtained through laboratory treatments modifying its structural parameters, oxygen (O)‐containing functional groups and nitrogen (N) content. The treatments included acetylation, amidation, ammonia fixation, methylation, nitration, oximation, sulphonation, and selective degradations. The transformed humic products were characterized by routine laboratory analyses. Then, plant yield and different properties of two soils treated with the corresponding potassium (K)‐humates were determined in greenhouse experiments. The main effects and interactions between parameters affecting the response of soil and plant to humic acid application were analyzed through factorial designs. Whereas the application rate (2 to 4 Mg/ha) had no great bearing on plant yield (accounting for between 84 to 176% of the untreated soils), the opposite occurred with aggregate stability and cation exchange capacity. Among the parameters examined in the humic acids, the hydrogen/carbo...

Specific N-methylations of HPV-16 E7 peptides alter binding to the retinoblastoma suppressor protein.

Complex formation between the human papilloma virus type 16 E7 protein (HPV-16 E7) and the retinoblastoma growth suppressor protein (RB) is believed to contribute to the process of cellular transformation that leads to cervical carcinoma. Genetic analysis of the HPV-16 E7 protein has shown that the segment of E7 homologous to the conserved region 2 of adenovirus 5 E1A protein is involved in both RB binding and E7-mediated cell transformation. We have previously shown that a peptide colinear with HPV-16 E7 residues 21-29 was able to block immobilized species of E7 from binding to RB protein. The current study reports the effects of different chemical modifications of this peptide. One type of modification, methylation of the alpha-amino nitrogens contributed by Leu22, Tyr25, and Leu28, resulted in a 45-fold increase in E7/RB binding antagonist activity. This increased antagonist activity is sequence-specific since methylation of the amino groups contributed by Tyr23, Cys24, or Glu26 resulted in a profound loss of binding antagonist activity. Using a newly developed binding assay we determined that the apparent dissociation constant for recombinant HPV-16 E7 protein binding to recombinant human RB protein is 1.3 nM. The peptide Ac[N-MeLeu22,N-Me-Tyr25,N-MeLeu28]-(21-29)-E7 amide was determined to be a competitive inhibitor of HPV-16 E7 binding to RB with a Ki value of 32 nM.

Proteolytic activity and immunoreactivity of chemically modified papain.

The effect of different chemical modifications of papain on the proteolytic activity and immunoreactivity has been studied. Modification with Dextran T 2000 caused increasing decline in proteolytic activity both with increasing degree of dextran oxidation and amount of bound dextran, whilst the immunoreactivity determined by nephelometry remained unchanged. Modification of papain with glutaraldehyde and formaldehyde causes rapid drops in both activities, even at very low concentrations of agents. Acetylation of papain showed expressive maxima of both proteolytic and immunochemical activities at the same degree of enzyme acetylation. Modification with diazobenzenesulfonic acid caused a high increase in immunoreactivity and a small increase in proteolytic activity.

Molecular Basis of B Cell Activation: Mitogenicity of Native and Modified Digitalis Glycosides

Lanatoside C, a digitalis glycoside, has previously been shown to be a potent polyclonal B cell activator for mouse lymphocytes. Since the chemical structure of lanatoside C is well defined we investigated the effect of different chemical modifications on the mitogenic properties of the glycoside in order to determine the molecular basis of B cell activation. The presence of an OH- group at C12 in the steroid nucleus proved to be essential for activation to occur in serum-free medium. Likewise, an intact carbohydrate side chain at C3 appeared to be necessary for retaining mitogenic properties. In serum-supplemented cultures, however, a much more complex response pattern was observed where the prerequisites for activation were not as distinct as in serum-free medium.