Bonds In Chain Research Articles

Gating Mechanism of the Voltage-Gated Proton Channel Studied by Molecular Dynamics Simulations.

The voltage-gated proton channel Hv1 has important roles in proton extrusion, pH homeostasis, sperm motility, and cancer progression. The Hv1 channel has also been found to be highly expressed in cell lines and tissue samples from patients with breast cancer. A high-resolution closed-state structure has been reported for the mouse Hv1 chimera channel (mHv1cc), solved by X-ray crystallography, but the open-state structure of Hv1 has not been solved. Since Hv1 is a promising drug target, various groups have proposed open conformations by molecular modeling and simulation studies. However, the gating mechanism and the open-state conformation under the membrane potential are still debate. Here, we present a molecular dynamics study considering membrane potential and pH conditions. The closed-state structure of mHv1cc was used to run molecular dynamics (MD) simulations with respect to electric field and pH conditions in order to investigate the mechanism of proton transfer. We observed a continuous hydrogen bond chain of water molecules called a water-wire to be formed through the channel pore in the channel opening, triggered by downward displacement of the S2 helix and upward movement of the S4 helix relative to other helices. Due to the movement of the S2 and S4 helices, the internal salt bridge network was rearranged, and the hydrophobic gating layers were destroyed. In line with previous experimental and simulation observations, our simulation results led us to propose a new gating mechanism for the Hv1 proton channel, and may provide valuable information for novel drug discovery.

THE EFFECTIVENESS OF PLASTIC WASTE PYROLYSIS REACTOR WITH A ZEOLITE CATALYST AS AN APPROPRIATE TECHNOLOGY IN PRODUCING KEROSENE

<p>Plastic waste is harmful to the environment due to its long-term decomposition process. Plastic waste is made out of hydrocarbon polymers, its chain bonds do not naturally decompose physically, chemically, or biologically. The plastic waste generated in Indonesia reaches up to 175,000 tons per day, in the long term effect this will cause environmental problems when not managed properly. The purpose of this study was to determine the effectiveness of a plastic waste pyrolysis reactor with a zeolite catalyst as an appropriate technology in producing kerosene. The samples are plastic bottles waste from the Cimahi campus’ area. The results of kerosene production from the first, second, and third treatment were 122 ml, 137 ml, and 160 ml respectively. Based on ANOVA bivariate test, a p-value of 0.00 was obtained, meaning there was a significant average difference in the amount of kerosene produced between each treatment. Based on The LSD Post-Hoc Test, the significance value of the mean between each group was 0.000 (p <0.05), meaning there was a significant difference in the average amount of kerosene produced between every treatment group, most significant difference is within the third treatment by 35.67.</p>

The effect of stretching and tie layer composition on adhesion strength of multi-layered films

Multilayer films are widely used in flexible packaging to provide an optimum balance of performance and cost. Orientation in the semi-solid state via tenter frame, double bubble, and machine direction orientation processes enhances barrier and mechanical properties and offers a means toward light weighting packaging structures. Interlayer adhesion of coextruded films, however, substantially decreases during the orientation as the generated new interfacial area decreases bond density and chain segments are stressed. A guideline is proposed that provides insight into how changes during orientation in chain segment penetration, entanglement, bond orientation, and density affect peel strength because of semi-solid state orientation. Examples are provided that use these insights to design novel tie resins with improved performance.

Dynamically disordered hydrogen bonds in the hureaulite-type phosphatic oxyhydroxide Mn5[(PO4)2(PO3(OH))2](HOH)4.

We report the temperature evolution of hydrogen bond (HB) chains and rings in Mn5[(PO4)2(PO3(OH))2](HOH)4 to reveal conduction pathways based on difference Fourier maps with neutron- and synchrotron x-ray diffraction data. Localized proton dynamics for the five distinct hydrogen sites were observed and identified in this study. Their temperature evaluation over ten orders of magnitude in time was followed by means of quasielastic neutron scattering, dielectric spectroscopy, and ab initio molecular dynamics. Two out of the five hydrogen sites are geometrically isolated and are not suitable for long-range proton conduction. Nevertheless, the detected dc conductivity points to long-range charge transport at elevated temperatures, which occurs most likely (1) over H4-H4 sites between semihelical HB chains (interchain-exchanges) and (2) by rotations of O1-H1 and site-exchanging H4-O10-O5 groups along each semihelical HB chain (intrachain-exchanges). The latter dynamics freeze into a proton-glass state at low temperatures. Rotational and site-exchanging motions of HOH and OH ligands seem to be facilitated by collective motions of framework polyhedra, which we detected by inelastic neutron scattering.

Characteristics of peat functional group in Padang Island, Indonesia

Peat is composed of a diverse range of polar and nonpolar groups. Nonpolar groups, particularly those composed of aliphatic structures, tend to associate with one another and are therefore water-repellent (hydrophobic), a property that increases with the length of the chain of bonds. The drying process causes the nonpolar groups to interact with each other and form a long chain of bonds, reducing the ability of peatlands to bind water. As a result, it is vital to understand the chemical characteristics and functional groups associated with hydrophilicity and hydrophobicity. The chemical analysis comprises the following: ash content (500°C combustion method), C-org using the combustion method, N-total by Kjeldahl method, actual pH with soil water ratio of 1:5, and cation exchange capacity with NH4Oac pH 4.0. Additionally, the pelletized peat was examined for its constituent groups using an FTIR spectra and the Flaig et al., method (1975). Soil pH values on Padang Island ranged from 3.61 to 4.35 and the content of bases Ca, Mg, K, and Na in oligotrophic peat is very low, especially in thick peat (0-5 m). C-organic levels on Padang Island peat ranged from 4.42 to 53.32 percent, according to the results of the analysis. Peat with a thickness 0-5 m has functional groups dominated by C-O from ester, eter, fenol, while peat with a thickness 5-7 m, 7-9 m, >9 m is dominated with H OH group bonds, free OH.

The effect of gamma irradiation on the electrical and mechanical properties of bismuth carbonate-silicone rubber

Silicone rubber samples loaded with three different concentrations of bismuth carbonate 30, 35, and 40 wt % are prepared and mixed by the compressive method. The effect of gamma irradiation on both mechanical and electrical properties are investigated. The obtained results showed that the hardness of rubber samples is increased with increasing both the bismuth concentration and gamma irradiation dose. At the same time, the Young modulus, the tensile strength, and fracture strain (elongation at break) are decreased. Decreasing the tensile strength with the gamma irradiation dose can be attributed to the increase of the degradation process resulting in the scission of bonds in the rubber chains. Although bismuth carbonate filler improves the mechanical properties of the aging resistance to gamma irradiation, at higher concentrations for each, a degradation process of rubber chains is more predominant than crosslinking. Also, increasing the gamma irradiation dose decreases the samples’ electrical resistivity and increases their electrical conductivity. Knowing the variation of the mechanical and electrical properties of the irradiated bismuth silicone rubber composite will assist in identifying the suitability of its use in several applications, such as radiation sterilization of the silicone rubber for medical usage.

Gamma radiation modification of cassava starch and its characterization

AbstractRadiation technology has been recognized as a potential tool to modify starches in order to enhance their solubility and enzymatic digestion, hence improving their applicability in food industry. In the present study, the local cassava starch was irradiated under 60Co gamma source with the absorbed dose ranging from 1 to 10 kGy, and the obtained radiation‐modified starches were characterized. The microstructure of the initial cassava starch was not much changed although several starch granules were deformed or even fragmented by gamma irradiation as observed in the scanning electron microscopy images. Water solubility of the irradiated starch was significantly increased, and their viscosity was much reduced by radiation degradation. Gamma radiation broke glycosidic bonds in starch chains into smaller molecules with lower molecular weight, whereby increased the water solubility of cassava starch. Radiation scission also partly decreased the crystallinity of the starches irradiated with dose higher than 5 kGy as indicated in their X‐ray diffraction patterns. The Fourier transform infrared spectra of irradiated starches revealed the reduction in intensities of stretching vibration characterized for OH, CH, and COC groups of starch molecules. Thus, gamma irradiation can be used to modify cassava starch for further applications.

Cryogenic infrared spectroscopy provides mechanistic insight into the fragmentation of phospholipid silver adducts

Tandem mass spectrometry is arguably the most important analytical tool for structure elucidation of lipids and other metabolites. By fragmenting intact lipid ions, valuable structural information such as the lipid class and fatty acyl composition are readily obtainable. The information content of a fragment spectrum can often be increased by the addition of metal cations. In particular, the use of silver ions is deeply rooted in the history of lipidomics due to their propensity to coordinate both electron-rich heteroatoms and C = C bonds in aliphatic chains. Not surprisingly, coordination of silver ions was found to enable the distinction of sn-isomers in glycerolipids by inducing reproducible intensity differences in the fragment spectra, which could, however, not be rationalized. Here, we investigate the fragmentation behaviors of silver-adducted sn- and double bond glycerophospholipid isomers by probing fragment structures using cryogenic gas-phase infrared (IR) spectroscopy. Our results confirm that neutral headgroup loss from silver-adducted glycerophospholipids leads to dioxolane-type fragments generated by intramolecular cyclization. By combining high-resolution IR spectroscopy and computational modelling of silver-adducted fragments, we offer qualitative explanations for different fragmentation behaviors of glycerophospholipid isomers. Overall, the results demonstrate that gas-phase IR spectroscopy of fragment ions can significantly contribute to our understanding of lipid dissociation mechanisms and the influence of coordinating cations.Graphical abstract

Low-temperature selective transformation of diethylbenzene to isobutane and cyclohexanes via the interplay of Pt and acid centres in Pt/H-*BEA zeolites

The hydrocracking of aromatic hydrocarbons on bifunctional catalysts comprises parallel reactions that provide a wide distribution of products and byproducts. This work demonstrates on diethylbenzene (DEB) hydrotreatment that Pt/H-Al-rich *BEA zeolite catalysts can significantly reduce the hydrocracking temperature so that only the selected reaction mechanisms prevail in the process, providing high selectivity. The interplay of high activity of Pt clusters in hydrogenation/dehydrogenation and Brønsted acid sites in acid-catalysed reactions allows selective hydrocracking of DEB to isobutane and methylcyclopentane by the paring reaction at 200 °C. Low-temperature hydrocracking consists of hydrogenation of DEB to diethylcyclohexane, its rapid skeletal hydroisomerization to C10 branched alkylcycloalkanes followed by their A type β scission providing isobutane and methylcyclopentane with 80% selectivity at 68% DEB conversion, practically without subsequent reactions of the formed products. The reactive CC bond in tribranched alkylcycloalkanes selectively undergoes A type β scission, while more stable CC bonds in less or unbranched hydrocarbon chains or rings do not crack to a substantial extent at low temperatures. The study demonstrates that the low-temperature hydrotreatment of aromatics over highly active catalysts allows controlling the involvement of individual reaction mechanisms in the complex hydrocracking process and provides tailored selectivity.

Metallic networks and hydrogen compensation in highly nonstoichiometric amorphous In2O3−x

The unique response of amorphous ionic oxides to changes in oxygen stoichiometry is investigated using computationally intensive ab initio molecular dynamics simulations, comprehensive structural analysis, and hybrid density-functional calculations for the oxygen defect formation energy and electronic properties of amorphous ${\mathrm{In}}_{2}{\mathrm{O}}_{3\ensuremath{-}x}$ with $x=0$--0.185. In marked contrast to nonstoichiometric crystalline nanocomposites with clusters of metallic inclusions inside an insulating matrix, the lack of oxygen in amorphous indium oxide is distributed between a large fraction of undercoordinated In atoms, leading to an extended shallow state for $x<0.037$, a variety of weakly and strongly localized states for $0.074<x<0.148$, and a percolation-like network of single-atom chains of metallic In-In bonds for $x>0.185$. The calculated carrier concentration increases from $3.3\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $x=0.037$ to $6.6\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $x=0.074$ and decreases only slightly at lower oxygen content. At the same time, the density of deep defects located between 1 and 2.5 eV below the Fermi level increases from $0.4\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $x=0.074$ to $2.2\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $x=0.185$. The wide range of localized gap states associated with various spatial distributions and individual structural characteristics of undercoordinated In is passivated by hydrogen that helps enhance electron velocity from $7.6\ifmmode\times\else\texttimes\fi{}{10}^{4}$ to $9.7\ifmmode\times\else\texttimes\fi{}{10}^{4}$ m/s and restore optical transparency within the visible range; H doping is also expected to improve the material's stability under thermal and bias stress.

Polyurethane Blended with Silica-Nanoparticle-Modified Graphene as a Flexible and Superhydrophobic Conductive Coating with a Self-Healing Ability for Sensing Applications

The introduction of self-healing ability into conductive materials has been the subject of great concern in recent years. In this work, a flexible and superhydrophobic nanocomposite coating with intrinsic and superficial dual self-healing ability was prepared. The fabric coating is empowered with the intrinsic self-healing ability that is performed by the disulfide bonds in the main chains of polyurethane (PU) as well as the multiple hydrogen bonds between silica-nanoparticle-modified graphene and PU. Meanwhile, the hydrophobic long chains in the side chains of PU can migrate on the surface to repair the superficial damaged parts of the coating. Owing to the integration of silica-nanoparticle-modified graphene and self-healing PU, the obtained multifunctional flexible coating not only shows excellent piezoresistive sensing performance but also exhibits superhydrophobic ability. This self-healing multifunctional flexible coating has potential applications in the fields of antistatic electricity, wearable electronics, battery, electromagnetic shielding, and so on.

Stimuli-Responsive Covalent Adaptable Hydrogels Based on Homolytic Bond Dissociation and Chain Transfer Reactions

Covalent adaptable hydrogels containing dynamic covalent bonds are gaining significant interest based on their ability of stimuli-controlled reversible bond dissociation, structural reorganization, color change, and self-healing through covalent bond exchange or dissociation. Potential applications of such hydrogels have been explored in coatings, sealants, tissue adhesives, soft robotics, tissue engineering, and stimuli-responsive lithography. Stimuli-induced homolytic bond cleavage leads to the formation of radicals with the ability of recombination or transfer to induce bond exchange and color variation. The incorporation of such stimuli-responsive homolytically cleavable bonds in hydrogels can lead to stimuli-controlled plasticity, stress relaxation, self-healing, structural reorganization, mechanochromism, and mechanoluminescence. The resultant smart materials are interesting for different applications, ranging from patterning and shape-shifting, cell encapsulation and culturing, and protein binding to strain sensing and damage reporting. The recent progress in the preparation of covalently adaptable hydrogels based on stimuli-responsive homolytical bond dissociation and recombination or chain transfer will be discussed in this review. More specifically, the different types of chemistry that can be used for development of covalent adaptable hydrogels based on light-induced, temperature-induced, and mechanically induced homolytic bond dissociation will be discussed. Moreover, the applications of the resultant covalent adaptable hydrogels will be highlighted, focusing on stress sensing and damage reporting, tissue engineering, and self-healable hydrogels, as well as stimuli-controlled patterning and shape-shifting.

Interfacial Adsorption and Electron Properties of Water Molecule/Cluster on Anatase TiO2(101) Surface: Raman and DFT Investigation.

The hydrogen bond network reconstruction at the titanium/water interface was monitored by Raman spectroscopy. In addition, the adsorption properties and the surface electron properties of hydrogen bond cluster (HBC) configurations were analyzed using adsorption energy, work function, Mulliken charge population, and density of states (DOS) by the first-principles method based on density functional theory (DFT). Our results show that the hydrogen bond network of the aqueous solution is reconstructed under the interaction with the anatase TiO2(101) surface with the transformation of the chain and free hydrogen bonds to complex hydrogen bonds. The adsorption energy of a single water molecule and HBC on the anatase TiO2(101) surface are the lowest with the 1-DD-h (-0.851 eV) and 3-D-h-DDA (-1.048 eV) configurations, respectively. Over the long term, artificially regulating the structure of the HBC might be an effective and general way to slow down the metal anodic reaction without surface modification. Furthermore, the surface charge concentrates on the bridging oxygen atom, which will be the active site of the interface reaction. It is helpful to clarify the anodic corrosion reaction mechanism of the titanium spontaneous oxide film/water interface.

Discovery of Polyoxypregnane Derivatives From Aspidopterys obcordata With Their Potential Antitumor Activity.

The bioassay-guided phytochemical study of an ethnic medicinal plant Aspidopterys obcorda ta Hemsl. var. obcordata results in the isolation of eight new polyoxypregnane derivatives, named aspidatasides A–H (1–8), along with ten known analogs (9–18). The series polyoxypregnane derivatives were screened for their cytoxic activity against HL-60 cells, and compound 2 showed the highest potency with an IC50 8.03 μM. Preliminary structure–activity relationship studies displayed that the sugar chain and double bond could notably impact their biological activity.

Allopeptimicins: unique antibacterial metabolites generated by hybrid PKS-NRPS, with original self-defense mechanism in Actinoallomurus.

In the search for structurally novel metabolites with antibacterial activity, innovative approaches must be implemented to increase the probability of discovering novel chemistry from microbial sources. Here we report on the application of metabolomic tools to the genus Actinoallomurus, a poorly explored member of the Actinobacteria. From examining extracts derived from 88 isolates belonging to this genus, we identified a family of cyclodepsipeptides acylated with a C20 polyketide chain, which we named allopeptimicins. These molecules possess unusual structural features, including several double bonds in the amino-polyketide chain and four non-proteinogenic amino acids in the octapeptide. Remarkably, allopeptimicins are produced as a complex of active and inactive congeners, the latter carrying a sulfate group on the polyketide amine. This modification is also a mechanism of self-protection in the producer strain. The structural uniqueness of allopeptimicins is reflected in a biosynthetic gene cluster showing a mosaic structure, with dedicated gene cassettes devoted to formation of specialized precursors and modular assembly lines related to those from different pathways.

Effect of the disulfide bond and polyethylene glycol on the degradation and biophysicochemical properties of polyurethane micelles.

The disulfide bond has emerged as a promising redox-sensitive switch for smart polymeric micelles, due to its properties of rapid response to the reductive environment and spatiotemporally-controlled therapeutic agent delivery. However, the dilemma of multifunctional nanomedicine is that the more intelligent the functionalities integrated into a system, the vaguer the understanding of the structure and interaction between the multi-functional moieties becomes. To better understand the interaction between the disulfide bond and methoxy polyethylene glycol (mPEG), and their effects on the biophysicochemical characterization of micelles, we developed a series of polyurethane micelles containing various densities of disulfide bonds and bearing different molecular weights of mPEG. In this work, we found that the critical factor determining the degradation rate of polymer micelles was the hydrophobic/hydrophilic ratio of broken polymer segments triggered by disulfide bond breaking. The higher density of the disulfide bond and longer mPEG chain accelerate the degradation process due to the disproportionate hydrophobic/hydrophilic ratio of the broken chain, which is the key factor to determine the micellization and stabilization of polymer micelles. This work provides a fundamental understanding of the interaction between the complex functional groups and a new insight into the mechanism of the micelle degradation process, offering guidance on the rational design and fabrication of multifunctional nanoformulations.

Crystal shapes, triglyphs, and twins in minerals: The case of pyrite

Abstract The euhedral shapes of pyrite FeS2 are usually exposing three main surfaces: striated (001), smooth (111), and striated (210), leading to the cubical, octahedral, and pyritohedral morphology, respectively. The macroscopic striations, sometimes called triglyphs on cubic crystals, are parallel on specific surfaces and aligned to the <100> directions. Other types of striated and unstriated (hkl) surfaces can be observed on pyrite crystals from Peru, a country offering a rich diversity of pyrite shapes. A rare specimen from Elba Island (Italy) is a pyritohedron with uncommon directions of striations (so-called “negative” striations, first described in Japanese minerals). The Wulff kinetic growth and the periodic bond chain (PBC) theories were not relevant enough to explain crystal shapes, the texture of the surfaces, and twinning. To bring some new insights on crystal growth, twinning, and anisotropy, pyrite samples are analyzed using XRD, SEM, and EDS techniques coupled with atomistic simulations. A first analysis points out that sulfur terminations play a key role in the growth of striations in distinguishing the six <001> directions. The negative striated pyritohedral pyrite would be, in fact, a special case that has stabilized the {120} surfaces, which are structurally different from the {210} facets. The {120} surface has a slightly higher surface energy than the {210} surface (surface energies of 1.68 and 1.65 J/m2, respectively, calculated with force field methods). {120} pyritohedra from Elba, Italy, are growing next to micaceous iron oxides (a type of hematite), which are also peculiar specimens with magnetic properties. Another specificity is that some rare earth elements have been identified in the pyrite sample from Elba, which leads to a hypothesis that geothermal conditions favor “negative” striations (e.g., discernible in Akita prefecture-Japan, Boyacá-Colombia, and Cassandra-Greece). The striation directions become useful to distinguish (hkl) surfaces and to identify twinning as they follow the same patterns on each interpenetrated crystal. The most common twinning is the “iron cross,” a penetration twin of two crystals defined by a rotation of 90° along an [001] axis with a coincidence in the iron sub-lattice (e.g., twinning by merohedry) and with a twin center. The sulfur network also plays a fundamental role in stabilizing the (001) interface and in keeping the chemical bulk properties at the boundary, as confirmed by additional ab initio simulations. The grain boundary is a 2D defect in which the (001) twinning is relatively stable as it is common. The calculated formation energy of the rotation twinning is 0.8 J/m2. The rotation twinning is associated with an apparent reflection on (110) planes. The formation energy of the (110) mirror grain boundary is 1.7 J/m2, and the interface at the atomic scale is relatively uniform in agreement with experimental observations.

Theoretical design and study of two-dimensional organic ferroelectric monolayer based on cyclobutene-1,2-dicarboxylic acid

Compared with traditional inorganic ferroelectric materials, organic molecular ferroelectric materials possess many advantages, such as light weight, flexibility, no heavy metal atoms and low cost, and have received extensive attention for a long time. In recent years, atomic-thick two-dimensional (2D) inorganic ferroelectric materials have achieved breakthrough and attracted much attention. However, there are few reports on the design and research of two-dimensional organic ferroelectric materials. In this paper, we theoretically propose a 2D monolayer organic ferroelectric molecular crystal with the cyclobutene-1,2-dicarboxylic acid (CBDC) molecules as the building block based on density functional theory calculations. The bulk of CBDC molecular crystals clearly shows layered structure due to the chain-like arrangement of hydrogen bonds in crystal. It is found that the internal hydrogen bond chains give rise to the anisotropic cleavage energy values along different crystal planes of the CBDC molecular crystal bulk. Theoretical calculation suggests that the CBDC based 2D monolayer organic ferroelectric molecular crystal can be achieved by the mechanical/chemical peeling along the (102) crystal plane because of the lowest cleavage energy. It is predicted that the in-plane spontaneous polarization of the CBDC (102) molecular crystal monolayer is ～0.39 × 10<sup>–6</sup> μC/cm, which is comparable to those of some inorganic counterparts. Calculations also indicate that the CBDC (102) molecular crystal monolayer shows a high polarization reversal barrier and is sensitive to the external uniaxial stress. The CBDC (102) monolayer organic ferroelectric molecular crystal reveals high in-plane spontaneous polarization with polarization reversal barrier easily modulated by the interface strain engineering, thereby rendering it great potential in lightweight, metal-free and flexible ferroelectric devices.

Influence of Temperature on the Properties of Cellulose Iβ based on Molecular Dynamics Simulations

Natural plants, such as cotton and linen, are rich in cellulose Iβ. The properties of cellulose Iβ under different temperatures was studied using molecular dynamics simulations. Firstly, the crystal of cellulose Iβ was built. To verify the model, the X-ray fibre diffraction and thermal expansion coefficients were calculated, which were found to agree with experimental results. Then the Mulliken population of the bonds were computed and the movement of the centre chain and hydrogen bonds studied over the range 300-550 K using a PCFF force field. The results of the Mulliken population reveal the three steps of pyrolysis. The higher the temperature is, the more intensely the movement of the centre chain is. However, the impact of temperature on the movement of the centre chain is not obvious. From 300 K to 550 K, the total number of hydrogen bonds decreased by only 20%. Moreocer, the rupture of intrachain hydrogen bonds and the formation of interchain hydrogen bonds at 400 K ~ 450 K temperature occurred.

Characterization, antioxidant, antineoplastic and immune activities of selenium modified Sagittaria sagittifolia L. polysaccharides

This study proposed an optimal way to supplement organic selenium, boost polysaccharides solubility, antioxidant, anticancer, immune responses. A purified polysaccharide fraction of Sagittaria sagittifolia L. (PSSP) was successfully modified with selenium (Se-PSSP), and its characteristics, antioxidant, antineoplastic and immune activities were studied. The structure and the monosaccharide composition were determined by means of UV–visible spectrometry, FT-IR spectra, NMR spectra, X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM) and atomic force microscope (AFM). The results showed that both PSSP and Se-PSSP contained a pyranoid polysaccharide linked by α-glycosidic bonds in the main chain. In addition, PSSP and Se-PSSP were amorphous morphology without three-helix conformation. PSSP (47.12 kDa) was mainly composed of glucose, mannose and xylose with molar percentages of 55.82%, 14.86% and 14.35%, respectively. Se-PSSP (16.82 kDa) is mainly composed of glucose, xylose and galactose with molar percentages of 26.49%, 18.76% and 18.14%, respectively. Compared with PSSP, Se-PSSP showed stronger water-solubility, antioxidant activity, cytotoxicity and immunomodulatory activity than that of PSSP. These results suggested that Se-PSSP is a promising novel Se-supplement and may be served as an excellent potential antioxidant, antineoplastic, and immunomodulatory agents in the field of functional foods and medicine industry.