Назад

Application of Bioactive Coatings Based on Chitosan for Soybean Seed Protection

Soybean seeds suffer attacks of various pests that result in a decreased yield in northeastern China. Until recently, people use pesticides such as insecticides to achieve the goal of controlling pests. Chitosan extracted from deacetylation of chitin is promising candidates as a seed-coating agent to control agrotis ypsilon, soybean pod borer, and soybean aphid effectively. An experimental study on influences of chitosan with different concentrations on pest controlling and soybean growth was made in the paper. Coating based on chitosan was used as a feeding deterrent and for enhancing the germination and quality of soybean seeds. Results indicated that all chitosan coating had a significant effect on antifeeding against pests; with the increasing concentration, antifeedant rate (AR) were increased obviously, especially when in the concentration of 5%, santifeedant rate of agrotis ypsilon, soybean pod borer, and soybean aphid reached 82.89%, 87.24%, and 80.21%, respectively. Also chitosan coating increased seed germination, plant growth, and soybean yield efficiently, especially when, in the concentration of 5%, the yield was increased by about 20% compared with CK. The application of chitosan in soybean seed coated is an appropriate option to control pests replacing high-toxicity pesticides and enhance soybean yield.
Автор: Defang Zeng, Xinrong Luo, and Renjie Tu 
Рік видання: 2012. Тип документу: Складова частина документу 
Розмір: 2,79 Мб     Кількість завантажень: 41

SelectiveModification of Chitosan to Enable the Formation of Chitosan-DNA Condensates by Electron Donator Stabilization

Chitosan, a polyaminosaccharide, has been investigated for its use in the field of drug-delivery and biomaterial applications because of its natural biocompatibility and polycationic properties. Chemical modifications of chitosan have been attempted in an effort to increase the transfection efficiency with respect to gene delivery applications; however, it is unknown how these modifications affect the formation of the condensates. This study attempts to determine the effects of modification of the cationic center of chitosan on the ability to condense DNA. Specifically, electron-donating or -withdrawing groups were used as modifiers of the cationic charge on the chitosan backbone to stabilize the protonated form of chitosan, which is necessary to form condensates and increase the efficiency of the polymer to condense DNA by yielding condensates at a lower nitrogen to phosphorous (N : P) ratio. While an N: P ratio of 7 is needed to condense DNA with unmodified chitosan, phthalate-modified chitosan yielded condensates were obtained at an N:P ratio of 1.0.
Автор: Karl E. Kador and Anuradha Subramanian 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 1,58 Мб     Кількість завантажень: 41

Effect of Addition of Boric Acid and Borax on Fire-Retardant andMechanical Properties of Urea Formaldehyde Saw Dust Composites

Properties of the flame retardant urea formaldehyde (UF) board made from saw dust fibers were investigated. Flame retardant chemicals that were evaluated include boric acid (BA) and borax (BX) which were incorporated with saw dust fibers tomanufacture experimental panels. Three concentration levels, (0.5, 1, and 5%) of fire retardants and 10% urea formaldehyde resin based on oven dry fiber weight were used to manufacture experimental panels. Physical and mechanical properties including water absorption, modulus of rupture (MOR), and modulus of elasticity (MOE) were determined. The results showed that water absorption and bending strength decreased as the flame retardant increased. The highest concentration of (BA + BX) enhanced the fire retardant more than the lower ones. Scanning electron microscope and FTIR of composite panels were studied.
Автор: Zenat A. Nagieb, Mona A. Nassar and Magda G. El-Meligy 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 1,59 Мб     Кількість завантажень: 41

Evaluation of the Functional Properties of Promising Dioscorea trifida L.Waxy Starches for Food Innovation

Few natural waxy starches are offered to the industry demand. Therefore, themorphological, physical, and chemical characteristics of “Mapuey” waxy starch were assessed. Amylose contents of starches isolated from Dioscorea trifida L. (“Mapuey”) landraces cultivated in the Amazons of Venezuela were lower (<8.1%) than commercial Mapuey starch (>8.7%). DSC onset gelatinization temperatures varied from 71.1 to 73.2◦C. All starches exhibited B-type patterns, with degrees of crystallinity varying from 28% to 33%. The highest crystallinity was found for the starches exhibiting the highest amylose content. At 90◦C, solubility and swelling power varied from2.3 to 4.3% and 20.9 to 32.8%, respectively. Gel clarity was variable from20.8 to 62.1%. A 5% starch suspension induced a high RVA peak viscosity between 1667 and 2037 cP. This natural waxy yam resource is a promising ingredient for food industry.
Автор: Elevina Perez, Olivier Gibert, Agn`es Rolland-Sabat´e, Xiomara Segovia, Teresa S´anchez, Max Reynes, and Dominique Dufour 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 1,92 Мб     Кількість завантажень: 41

Thiolactosides: Scaffolds for the Synthesis of Glycolipids in Animal Cells

Various glycolipids were synthesized using thiolactosides as scaffolds for glycosylation in animal cells. The basic building blocks, n-dodecyl β-D-thiolactoside (β-LacSC12) and n-dodecyl α-D-thiolactoside (α-LacSC12), were chemically synthesized in 2 steps: glycosylation followed by deacylation. The thiolactosides were administered to animal cells in culture and served as substrates for cellular enzyme-catalyzed glycosylation. Incubation of mouse melanoma B16 cells in the presence of β-LacSC12 or α-LacSC12 resulted in sialylation of the terminal galactose residue and gave a GM3-type ganglioside. Administration of β-Lac SC12 inMadin- Darby canine kidney (MDCK) cells likewise gave a GM3-type ganglioside. On the other hand, introduction of β-LacSC12 in African green monkey kidney (Vero) cells gave Gb3- and Gb4-type glycolipids aside from GM3-type ganglioside. In the course of the study, significant changes in B16 cell morphology and elevated secretion of melanin were also observed.
Автор: Masako Mori, Maria Carmelita Z. Kasuya, Mamoru Mizuno, and Kenichi Hatanaka 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 3,7 Мб     Кількість завантажень: 41

Chitosan-Based Macromolecular Biomaterials for the Regeneration of Chondroskeletal and Nerve Tissue

The use of materials, containing the biocompatible and bioresorbable biopolymer poly(1 → 4)-2-amino-2-deoxy-β-D-glucan, containing some N-acetyl-glucosamine units (chitosan, CHI) and/or its derivatives, to fabricate devices for the regeneration of bone, cartilage and nerve tissue, was reviewed. The CHI-containing devices, to be used for bone and cartilage regeneration and healing, were tested mainly for in vitro cell adhesion and proliferation and for insertion into animals; only the use of CHI in dental surgery has reached the clinical application. Regarding the nerve tissue, only a surgical repair of a 35 mm-long nerve defect in the median nerve of the right arm at elbow level with an artificial nerve graft, comprising an outer microporous conduit of CHI and internal oriented filaments of poly(glycolic acid), was reported. As a consequence, although many positive results have been obtained, much work must still be made, especially for the passage from the experimentation of the CHI-based devices, in vitro and in animals, to their clinical application.
Автор: Giulio D. Guerra, Niccoletta Barbani, Mariacristina Gagliardi, Elisabetta Rosellini, and Caterina Cristallini 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 557 Кб     Кількість завантажень: 41

Convenient Approach to Access Octa-Glycosylated Porphyrins via “Click Chemistry”

Easy, quantitative, and one-pot introduction of eight β-lactoside-modules onto a porphyrin-core was achieved through Cu+- catalyzed chemoselective coupling (click chemistry) between a porphyrin carrying eight alkyne-terminals and β-lactosyl azides. The obtained porphyrin-based glycocluster shows not only good water-solubility but also strong/specific lectin-affinity.
Автор: Misako Okada, Yuko Kishibe, Kanako Ide, Toshiyuki Takahashi, and Teruaki Hasegawa 
Рік видання: 2009. Тип документу: Складова частина документу 
Розмір: 1,43 Мб     Кількість завантажень: 41

On the Conformational Properties of Amylose and Cellulose Oligomers in Solution

Molecular dynamics (MD) simulations were used to monitor the stability and conformation of double-stranded and singlestranded amyloses and single-stranded cellulose oligomers containing 9 sugar moieties in solution as a function of solvent composition, ionic strength, temperature, and methylation state. This study along with other previous studies suggests that hydrogen bonds are crucial for guaranteeing the stability of the amylose double helix. Single-stranded amylose forms a helical structure as well, and cellulose stays highly elongated throughout the simulation time, a behavior that was also observed experimentally. In terms of coordination of solute hydroxyl groups with ions, amylose shows entropy-driven coordination of calcium and sulfate ions, whereas cellulose-ion coordination seems to be enthalpy-dominated. This indicates that entropy considerations cannot be neglected when explaining the structural differences between amyloses and celluloses.
Автор: MoritzWinger,Markus Christen, and Wilfred F. van Gunsteren 
Рік видання: 2009. Тип документу: Складова частина документу 
Розмір: 2,05 Мб     Кількість завантажень: 41

Quaternary Salts of Chitosan: History, Antimicrobial Features, and Prospects

Recently, increasing attention has been paid to water-soluble derivatives of chitosan at its applications. The chemical characteristics and the antimicrobial properties of these salts can play significant role in pharmacological and food areas mainly as carriers for drug delivery systems and as antimicrobial packaging materials. In the current paper, a historical sequence of the main preparative methods, physical chemistry aspects, and antimicrobial activity of chitosan quaternized derivatives are presented and briefly discussed. In general, the results indicated that the quaternary derivatives had better inhibitory effects than the unmodified chitosan.
Автор: Douglas de Britto, Rejane Celi Goy, Sergio Paulo Campana Filho, and Odilio B. G. Assis 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 1,52 Мб     Кількість завантажень: 41

γ-Cyclodextrin Increases Hydrolysis of Gangliosides by Sialidase from Arthrobacter ureafaciens: Hydrolysis of Gangliosides

Sialidase is a ubiquitous enzyme that catalyzes the hydrolytic removal of terminal sialic acid residues from oligosaccharides in glycolipids and glycoproteins. Ganglioside GM1 has been usually found to be resistant to various sialidases. Arthrobacter ureafaciens sialidase has been reported to remove sialyl residues of ganglioside GM1 in the presence of bile salts. However, bile salts are difficult to be removed, and disturb HPTLC analysis.Using γ-cyclodextrin (γ-CD) as a novel additive agent, ganglioside GM1 was efficiently hydrolyzed to asialo-GM1 by A. ureafaciens sialidase.
Автор: Rie Mitsumori, Tomohisa Kato, and Kenichi Hatanaka 
Рік видання: 2009. Тип документу: Складова частина документу 
Розмір: 819 Кб     Кількість завантажень: 41

A Biopolymer Chitosan and Its Derivatives as Promising Antimicrobial Agents against Plant Pathogens and Their Applications in Crop Protection

Recently, much attention has been paid to chitosan as a potential polysaccharide resource. Although several efforts have been reported to prepare functional derivatives of chitosan by chemical modifications, few attained their antimicrobial activity against plant pathogens. The present paper aims to present an overview of the antimicrobial effects, mechanisms, and applications of a biopolymer chitosan and its derivatives in crop protection. In addition, this paper takes a closer look at the physiochemical properties and chemicalmodifications of chitosan molecule. The recent growth in this field and the latest research papers published will be introduced and discussed.
Автор: Mohamed E. I. Badawy and Entsar I. Rabea 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 922 Кб     Кількість завантажень: 41

High-Performance Anion-Exchange Chromatography Coupled with Pulsed Electrochemical Detection as a Powerful Tool to Evaluate Carbohydrates of Food Interest: Principles and Applications

Specific HPLC approaches are essential for carbohydrate characterization in food products. Carbohydrates are weak acids with pKa values in the range 12–14 and, consequently, at high pH can be transformed into oxyanions, and can be readily separated using highly efficient anion-exchange columns. Electrochemical detection in HPLC has been proven to be a powerful analytical technique for the determination of compounds containing electroactive groups; pulsed amperometric detection of carbohydrates is favourably performed by taking advantage of their electrocatalytic oxidation mechanism at a gold working electrode in a basic media. High-performance Anion Exchange Chromatography (HPAEC) at high pH coupled with pulsed electrochemical detection (PED) is one of the most useful techniques for carbohydrate determination either for routine monitoring or research application. This technique has been of a great impact on the analysis of oligo- and polysaccharides. The compatibility of electrochemical detection with gradient elution, coupled with the high selectivity of the anion-exchange stationary phases, allows mixtures of simple sugars, oligo- and polysaccharides to be separated with high resolution in a single run. A few reviews have been written on HPAEC-PED of carbohydrates of food interest in the last years. In this paper the recent developments in this field are examined.
Автор: Claudio Corradini, Antonella Cavazza, and Chiara Bignardi 
Рік видання: 2012. Тип документу: Складова частина документу 
Розмір: 1,21 Мб     Кількість завантажень: 41

Isolation and Structural Analysis In Vivo of Newly Synthesized Fructooligosaccharides in Onion Bulbs Tissues (Allium cepa L.) during Storage


Автор: Masaki Fujishima, Kensuke Furuyama, Yojiro Ishihiro, Shuichi Onodera, Eri Fukushi, Noureddine Benkeblia, and Norio Shiomi 
Рік видання: 2009. Тип документу: Складова частина документу 
Розмір: 1,59 Мб     Кількість завантажень: 41

Koenigs-Knorr Glycosylation with Neuraminic Acid Derivatives

Earlier we reported a convenient and efficient method of preparing α2-6 sialooligosaccharides in conditions of Koenigs-Knorr reaction. The use of Ag2CO3 allowed carrying out α2-6 sialylation of galacto-4,6-diol of mono- and disaccharides with chloride of acetylated N-acetylneuraminic acid methyl ester as glycosyl donor. In this study we applied this approach to other derivatives of neuraminic acid, namely, Neu5Gc, 9-deoxy-9-NAc-Neu5Ac, Neu5Acα2-8Neu5Ac, and Neu5Acα2-8Neu5Acα2-8Neu5Ac as glycosyl donors; eight compounds were synthesized: Neu5Gcα-O(CH2)3NH2 (8), Neu5Gcα2-6Galβ1-4GlcNAcβ-O(CH2)3NH2 (10), 9-deoxy-9-NAc-Neu5Ac-O(CH2)3NH2 (15), 9-deoxy-9-NAc-Neu5Acα2-6Galβ1-4GlcNAcβ-O(CH2)3NH2 (17), Neu5Acα2- 8Neu5Acα-O(CH2)3NH2(23) Neu5Acα2-8Neu5Acα-OCH3 (24), Neu5Acα2-8Neu5Acα-OCH2(p-C6H4)NHCOCH2NH2 (25), and Neu5Acα2-8Neu5Acα2-8Neu5Acα-O(CH2)3NH2 (32). These sialosides were used for characterization of siglecs and other carbohydrate-binding proteins.
Автор: Galina Pazynina, Vitaly Nasonov, Ivan Belyanchikov, Reinchard Brossmer, Maxim Maisel, Alexander Tuzikov, and Nicolai Bovin 
Рік видання: 2010. Тип документу: Складова частина документу 
Розмір: 744 Кб     Кількість завантажень: 41

Identification and Quantification of Protein Glycosylation

Glycosylation is one of the most abundant posttranslation modifications of proteins, and accumulating evidence indicate that the vast majority of proteins in eukaryotes are glycosylated. Glycosylation plays a role in protein folding, interaction, stability, and mobility, as well as in signal transduction. Thus, by regulating protein activity, glycosylation is involved in the normal functioning of the cell and in the development of diseases. Indeed, in the past few decades there has been a growing realization of the importance of protein glycosylation, as aberrant glycosylation has been implicated in metabolic, neurodegenerative, and neoplastic diseases. Thus, the identification and quantification of protein-borne oligosaccharides have become increasingly important both in the basic sciences of biochemistry and glycobiology and in the applicative sciences, particularly biomedicine and biotechnology. Here, we review the state-of-the-art methodologies for the identification and quantification of oligosaccharides, specifically N- and Oglycosylated proteins.
Автор: Ziv Roth, Galit Yehezkel, and Isam Khalaila 
Рік видання: 2012. Тип документу: Складова частина документу 
Розмір: 801 Кб     Кількість завантажень: 41

Study of Antibacterial Efficacy of Hybrid Chitosan-Silver Nanoparticles for Prevention of Specific Biofilm and Water Purification

Antibacterial efficacy of silver nanoparticles (Ag NPs) deposited alternatively layer by layer (LBL) on chitosan polymer in the form of a thin film over a quartz plate and stainless steel strip has been studied. An eight-bilayer chitosan/silver (Cs/Ag)8 hybrid was prepared having a known concentration of silver. Techniques such as UV-visible spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES), and atomic force microscopy (AFM) were carried out to understand and elucidate the physical nature of the film. Gram-negative bacteria, Escherichia coli (E. coli), were used as a test sample in saline solution for antibacterial studies. The growth inhibition at different intervals of contact time and, more importantly, the antibacterial properties of the hybrid film on repeated cycling in saline solution have been demonstrated. AFM studies are carried out for the first time on the microbe to know the morphological changes affected by the hybrid film. The hybrid films on aging (3 months) are found to be as bioactive as before. Cytotoxicity experiments indicated good biocompatibility. The hybrid can be a promising bioactive material for the prevention of biofilms specific to E. coli and in purification of water for safe drinking.
Автор: Somnath Ghosh, Tasneem Kausar Ranebennur, and H. N. Vasan 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 3,55 Мб     Кількість завантажень: 41

Conformational Search on the Lewis X Structure by Molecular Dynamic: Study of Tri- and Pentasaccharide

Carbohydrates play vital roles in many biological processes, such as recognition, adhesion, and signalling between cells. The Lewis X determinant is a trisaccharide fragment implicated as a specific differentiation antigen, tumor antigen, and key component of the ligand for the endothelial leukocyte adhesion molecule, so it is necessary or essential to determine and to know their conformational and structural properties. In this work, conformational analysis was performed using molecular dynamics (MD) simulation with the AMBER10 program package in order to study the dynamic behavior of of the Lewis X trisaccharide (β-D-Gal- (1,4)-[α-L-Fuc-(1,3)]-β-D-GlcNAc-OMe) and the Lewis X pentasaccharide (β-D-Gal-(1,4)-[α-L-Fuc-(1,3)]-β-D-GlcNAc-(1,3)- β-D-Gal-(1,4)-β-D-Glu-OMe) in explicit water model at 300 K for 10 ns using the GLYCAM 06 force field.
Автор: N. Khebichat, K. Nekkaz, and S. Ghalem 
Рік видання: 2012. Тип документу: Складова частина документу 
Розмір: 3,48 Мб     Кількість завантажень: 41

Endogenous and Exogenous CD1-Binding Glycolipids

In the same way that peptide antigens are presented by major histocompatibility complex (MHC) molecules, glycolipid antigens can also activate the immune response via binding to CD1 proteins on antigen-presenting cells (APCs) and stimulate CD1- restricted T cells. In humans, there are fivemembers of the CD1 family, termed CD1a–e, of which CD1a–d are involved in glycolipid presentation at the cell surface, while CD1e is involved in the intracellular trafficking of glycolipid antigens. Both endogenous (self-derived) and exogenous (non-self-derived) glycolipids have been shown to bind to members of the CD1 family with varying degrees of specificity. In this paper we focus on the key glycolipids that bind to the different members of the CD1 family.
Автор: Janice M. H. Cheng, Ashna A. Khan, Mattie S. M. Timmer, and Bridget L. Stocker 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 985 Кб     Кількість завантажень: 41

Chitosan and Chitosan Derivatives for Biological Applications: Chemistry and Functionalization


Автор: Bruno Sarmento, Francisco M. Goycoolea, Alejandro Sosnik, and Jos´e dasNeves 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 421 Кб     Кількість завантажень: 41

Consequences of Neutralization on the Proliferation and Cytoskeletal Organization of Chondrocytes on Chitosan-Based Matrices

In tissue engineering strategies that seek to repair or regenerate native tissues, adhesion of cells to scaffolds or matrices is essential and has the potential to influence subsequent cellular events. Our focus in this paper is to better understand the impact of cellular seeding and adhesion in the context of cartilage tissue engineering. When scaffolds or surfaces are constructed from chitosan, the scaffolds must be first neutralized with sodium hydroxide and then washed copiously to render the surface, cell compatible. We seek to better understand the effect of surface pretreatment regimen on the cellular response to chitosan-based surfaces. In the present paper, sodium hydroxide concentration was varied between 0.1M and 0.5M and two different contacting times were studied: 10 minutes and 30 minutes. The different pretreatment conditions were noted to affect cell proliferation, morphology, and cytoskeletal distribution. An optimal set of experimental parameters were noted for improving cell growth on scaffolds.
Автор: Sandra E. Noriega and Anuradha Subramanian 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 6,03 Мб     Кількість завантажень: 41

Preparation and Characterization of Chitosan/Zinc Oxide Nanoparticles for Imparting Antimicrobial and UV Protection to Cotton Fabric

Synthesis of chitosan/ZnO nanoparticles was performed using different concentrations of ZnO at different temperatures. Nanoparticles of ZnO/chitosan were prepared in rod form with average length 60nm and average width 5–15 nm. Thus, obtained nanoparticles of ZnO/chitosan were characterized using UV spectrophotometer, FTIR, TEM, X-ray, and SEM. Size and shape of chitosan/ZnO nanoparticles relied on conditions of their synthesis. Notably, chitosan/ZnO in rod form with average length of 60nm and average width 5–15 nm could be achieved. Application of chitosan/ZnO nanoparticles to cotton fabric conferred on the latter antibacterial and UV protection properties. Cotton fabric was characterized using SEM, ultraviolet protection factor (UPF) rating, and antibacterial (gram-positive and gram-negative) characteristics. Finished cotton fabric exhibited good antibacterial properties against gram-positive and gram-negative bacteria. The UV testes indicated a significant improvement in UV protection of finished cotton fabric which is increasing by increasing the concentration of nanoparticles of ZnO/chitosan.
Автор: M. M. AbdElhady 
Рік видання: 2012. Тип документу: Складова частина документу 
Розмір: 1,91 Мб     Кількість завантажень: 41

Chitosan-Grafted Copolymers and Chitosan-Ligand Conjugates as Matrices for Pulmonary Drug Delivery

Recently, much attention has been given to pulmonary drug delivery by means of nanosized systems to treat both local and systemic diseases. Among the differentmaterials used for the production of nanocarriers, chitosan enjoys high popularity due to its inherent characteristics such as biocompatibility, biodegradability, and mucoadhesion, among others. Through the modification of chitosan chemical structure, either by the addition of new chemical groups or by the functionalization with ligands, it is possible to obtain derivatives with advantageous and specific characteristics for pulmonary administration. In this paper, we discuss the advantages of using chitosan for nanotechnology-based pulmonary delivery of drugs and summarize the most recent and promising modifications performed to the chitosan molecule in order to improve its characteristics.
Автор: Fernanda Andrade, Francisco Goycoolea, Diego A. Chiappetta, Jos´e das Neves, Alejandro Sosnik, and Bruno Sarmento 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 1,21 Мб     Кількість завантажень: 41

Bronsted Acidic Ionic Liquid 1-(1-Propylsulfonic)-3-methylimidazolium-Chloride Catalyzed Hydrolysisof D-Cellobiose in Aqueous Medium

Bronsted acidic ionic liquid 1-(1-propylsulfonic)-3-methylimidazolium chloride (PSMIMCl) shows a higher catalytic activity than sulfuric acid in the hydrolysis of D-cellobiose to D-glucose in water at 90–120◦C. This catalytic activity enhancement is more significant at higher temperatures, and at 120◦C, PSMIMCl produced 64.5% glucose yield, whereas H2SO4 produced only 42.2% after 40min. reaction, and this is a 52.8% enhancement of catalytic activity due to the alkylimidazolium group attached to the sulfonic acid group. 1H NMR monitoring of the D-cellobiose hydrolysis in PSMIMCl and sulfuric acid mediums failed to reveal intermediates in the hydrolysis reaction, and this is probably due to rapid conversion of the intermediate(s) to a mixture of Dglucose anomers with α : β ≈ 1 : 1.6.
Автор: Ananda S. Amarasekara and Bernard Wiredu 
Рік видання: 2012. Тип документу: Складова частина документу 
Розмір: 876 Кб     Кількість завантажень: 41

Structure and Dynamics of Glycosphingolipids in Lipid Bilayers: Insights from Molecular Dynamics Simulations

Glycolipids are important constituents of biological membranes, and understanding their structure and dynamics in lipid bilayers provides insights into their physiological and pathological roles. Experimental techniques have provided details into their behavior at model and biological membranes; however, computer simulations are needed to gain atomic level insights. This paper summarizes the insights obtained from MD simulations into the conformational and orientational dynamics of glycosphingolipids and their exposure, hydration, and hydrogen-bonding interactions in membrane environment. The organization of glycosphingolipids in raft-like membranes and their modulation of lipid membrane structure are also reviewed.
Автор: Ronak Y. Patel and Petety V. Balaji 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 5,04 Мб     Кількість завантажень: 41

Pectin Rhamnogalacturonan II: On the “Small Stemwith Four Branches” in the Primary Cell Walls of Plants

Rhamnogalacturonan II (RG-II) is a type of block copolymer of complex pectins that represents a quantitativelyminor component of the primary cell walls of land (vascular) plants. The structural composition of RG-II is almost totally sequenced and appears to be remarkably conserved in all tracheophytes so far examined. The backbone of RG-II, released from complex (cell wall) pectins by endo-polygalacturonase (Endo-PG) treatment, has been found to contain up to 15 (1→4)-linked-α-d-GalpA units, some of which carry four well-defined side chains, often referred to as A-, B-, C-, and D-side chains. Nevertheless, the relative locations on the backbone of these four branches, especially the A chain, remain to be ascertained. A combination of different data suggests that neither the terminal nonreducing GalA nor the contiguous GalA unit is likely to be the branching point of the A chain, but probably the ninth GalA residue from the reducing end, assuming a minimum backbone length of 11 (1→4)- linked-α-d-GalpA. The latest reports on RG-II are here highlighted, with a provided update for the macrostructure and array of functionalities.
Автор: Beda M. Yapo 
Рік видання: 2011. Тип документу: Складова частина документу 
Розмір: 754 Кб     Кількість завантажень: 41