Kinds Of Side Chains Research Articles

Structural characterization of a water-soluble acidic polysaccharide CSP-IV with potential anticoagulant activity from fruit pulp of Clausena lansium (Lour.) Skeels Guifei

Four main water-soluble wampee fruit pulp polysaccharides, named CSP-I, CSP-II, CSP-III and CSP-IV, were isolated from Clausena lansium (Lour.) Skeels Guifei, therein CSP-IV content was higher than the others. All components possess certain anticoagulant activity demonstrated by prolonged activated partial thromboplastin time, especially CSP-IV, which suggests that CSP-IV plays anticoagulant effect through disturbing intrinsic coagulation pathway. The wampee polysaccharide CSP-IV with Mw of 510.1 kDa was mainly composed of Gal, Ara and GalA. Backbone of CSP-IV contains Gal, Ara and GalA, two kinds of side chains contain one monosaccharide Gal or Ara, both branch on Gal residue of backbone. CSP-IV has no the conformation of triple helix demonstrated by Congo red test. These results showed that CSP-IV is an acidic polysaccharide with potential anticoagulant activity via targeting intrinsic coagulation pathway.

Side‐chain engineering of supramonomers enables tailorable cross‐linked supramolecular polyureas

AbstractThe integration of tailorable mechanical properties, dimensional stability, and reprocessability is of significance in the design of sustainable polymer materials. Herein, side‐chain engineering is employed to fabricate cross‐linked supramolecular polymers with customizable mechanical properties. Three kinds of side chains, including methyl, 1‐ethyl pentyl, and 1‐hexyl nonyl, are used to modify the supramonomers. Through the copolymerization of low‐content supramonomers and covalent monomers, cross‐linked supramolecular polyureas with a wide range of mechanical properties spanning from rigid plastics to elastic materials are successfully constructed. Specifically, the Young's modulus can be adjusted from 525 to 128 MPa by tuning the side chain of supramonomers from methyl to 1‐hexyl nonyl. Meanwhile, the materials still retain exceptional recyclability and solvent resistance. Even after seven generations of recycling processes, the reprocessed cross‐linked supramolecular polyureas maintain over 95% of their original mechanical properties. It is anticipated that side‐chain engineering is a facile method for designing customized polymer materials to achieve both tailored mechanical properties and desirable functions.

Proton Conductivity of Porous Zirconium‐Organic Frameworks Filled with Protic Ionic Liquid

AbstractInfiltration of the protic ionic liquid (PIL) triethylammmonium trifluoromethanesulfonate (TEA‐TFA) into the pores of zirconium metal organic‐frameworks (Zr‐MOFs) featuring interpenetrated networks, so‐called PIZOFs, leads to highly proton conducting dry solids. In case of PIZOFs their modular synthesis allows tailoring the environment in the pores via the chemical nature of the side chains at the organic linkers. By infiltration of different PIZOFs with 50 wt % of the PIL, nanocomposites exhibiting high proton conductivity under anhydrous conditions were obtained. The proton conductivity strongly depends on the chemical nature of the PIZOF pores, i.e., the kind of side chains at the linkers. Gas adsorption studies show that the side chains strongly influence the porosity and the hydrophilicity of the PIZOF materials.

Molecular Dynamics Study on the Water Mobility and Side-Chain Flexibility of Hydrated Poly(ω-methoxyalkyl acrylate)s.

Intermediate water (IW) is known to play an important role in the antifouling property of biocompatible polymers. However, how IW prevents protein adsorption is still unclear. To understand the role of IW in the antifouling mechanism, molecular dynamics simulation was used to investigate the dynamic properties of water and side-chains for hydrated poly(ω-methoxyalkyl acrylate)s (PMCxA, where x indicates the number of methylene carbons) with x = 1-6 and poly(n-butyl acrylate) (PBA) in this study. Since the polymers uptake more water than their equilibrium water content (EWC) at the polymer/water interface, we analyzed the hydrated polymers at a water content higher than that of EWC. It was found that the water molecules interacting with one polymer oxygen atom (BW1), of which most are IW molecules, in PMC2A exhibit the lowest mobility, while those in PBA and PMC1A show a higher mobility. The result was consistent with the expectation that the biocompatible polymer with a long-resident hydration layer possesses good antifouling property. Through the detailed analysis of side-chain binding with three different types of BW1 molecules, we found that the amount of side-chains simultaneously interacting with two BW1 molecules, which exhibit the highest flexibility among the three kinds of side-chains, is the lowest for PMC1A. The high mobility of BW1 is thus suggested as the main factor for the poor protein adsorption resistance of PMC1A even though it possesses enough IW content and relatively flexible side-chains. Contrarily, a maximum amount of side-chains simultaneously interacting with two BW1 molecules was found in the hydrated PMC3A. The moderate side-chain length of PMC3A allows side-chains to simultaneously interact with two BW1 molecules and minimizes the hydrophobic part attractively interacting with a protein at the polymer/water interface. The unique structure of PMC3A may be the reason causing the best protein adsorption resistance among the PMCxAs.

Rheological properties and self-assembled structures of a newly synthesized organogelator: cyclohexane carboxamido-2C8/oleyl in different solvent oils

We synthesized a low-molecular-mass organogelator, cyclohexanecarboxamide (HPMDA-R), which is composed of four amide groups with two kinds of side chains (R and R′). We selected two different alkyl groups, 2-ethylhexyl and oleyl, as side chains, considering the solubility and formation of a self-assembled structure within the solvents. We measured the rheological properties of HPMDA-2C8/oleyl dissolved in paraffin oil and three kinds of ester oils as solvents. The results indicated that the compound contributed to viscoelasticity in both isododecane and 2-ethylhexyl isononanoate, but increased viscosity only in cetyl caprylate. In addition, the compound behaved as a gelator for isostearyl isostearate. We were able to associate differences in function with the morphology of self-assembly observed by TEM. The formation of a gel may have contributed to the presence of the minute network structure. Our measurements for time-dependency supported that notion.

Effects of Different Unsaturated‐Linker‐Containing Donors on Electronic Properties of Benzobisthiadiazole‐Based Copolymers

AbstractA series of new copolymers with unsaturated‐linker‐containing donors and benzobisthiadiazole acceptors are synthesized. Two kinds of side chains (2‐octyl‐1‐dodecyl chain and siloxane‐terminated hexyl chain) are added to the polymer backbone. The introduction of unsaturated‐linker‐containing donor enhances the rigidity of the copolymers. The strong electron‐withdrawing benzobisthiadiazole units make these copolymers display very narrow bandgaps in the range of 0.75–1.26 eV. Bottom‐gate and bottom‐contact transistors based on these polymers exhibit p‐type field‐effect behavior with hole mobilities up to 1.17 × 10−3 cm2 V−1 s−1.

Narrow band-gap copolymers with two acceptors of benzo[1,2-c;3,4-c′]bis[1,2,5]thiadiazole and Benzo[c][1,2,5] thiadiazole: Synthesis, characteristics and application in field-effect transistors

A series of copolymers containing two acceptors (benzo[1,2-c;3,4-c′]bis[1,2,5] thiadiazole and benzo[c][1,2,5]thiadiazole are designed and synthesized. Two kinds of side chains (2-octyl-1-dodecyl chain and siloxane-terminated hexyl chain) are added to the copolymer backbone. Both polymers show very narrow band gaps of ∼1.0 eV. Bottom-gate and bottom-contact transistors based on the polymers are fabricated and exhibit p-type filed-effect behavior with hole mobility up to 1.04 × 10−2 cm2V−1s−1.

Novel Dual-Grafted Copolymer Bearing Glassy Polystyrene and Crystalline Poly(Ethylene Oxide) as Side Chains

A novel grafted copolymer with two different types of side chains was synthesized via a combination of grafting-onto and grafting-from strategy. Graft copolymer with one side chains polybutadiene-graft-polystyrene (PB-g-PS) was first synthesized though the grafting-onto method. Following the subsequent grafting-from method, the second kind of side chain was introduced to the copolymer with anionic ring open polymerization of ethylene oxide, obtaining dual-grafted copolymer polybutadiene-graft-(polystyrene; poly(ethylene oxide)) (PB-g-(PS;PEO)). By this combined strategy, linear and star-shaped dual-grafted copolymer were synthesized. The resulting dual-grafted copolymers had controlled molecular weights and narrow molecular weight distributions (Mw/Mn < 1.20). The thermal behavior of this dual-grafted copolymer bearing glassy and crystalline side chains was determined by differential scanning calorimetry (DSC), revealing that poly(ethylene oxide) grafts underwent confined crystallization, and the star-shaped copolymer had more confinement effects than did the linear ones.

New alternating copolymers of fluorene and triphenylamine bearing terthiophene and acceptor groups in the side chains: Synthesis and photovoltaic properties

A series of conjugated copolymers ( P1 and P2-CN–P4-CN) were prepared, in which two kinds of side chains were designed: one was the repeating units similar to that of P3HT, with the aim to increase the compatible with PC 61BM and the hole mobility; another one was the acceptor groups connected with the electron-rich backbone through the conjugated 3,4-ethylenedioxythiophene bridge, in order to broaden the absorption and lower the LUMO level. By controlling the ratios of these two kinds of side chains, the absorption band of the resultant conjugated polymers could be fine-tuned, while their energy levels nearly remained unchanged. As the result, the performance of the corresponding devices increased first, then decreased, indicating that there would be a balance between the different function of these two side chains.

Polymerization of α‐Hydroxy Acids by Ribosomes

Over 30 years ago, Fahnestock and Rich reported intriguing data showing the capability of the ribosome to polymerize phenyllactic acid. Although the polymerization was initiated and terminated randomly on polyuridic acids, the given data convincingly suggested that the generated polymer was composed of an approximately 7:3 mixture of phenyllactic acid and phenylalanine. Despite the fact that Fahnestock's conclusion was very likely correct, there have been no reports to follow up the ribosome-catalyzed polymerization of alpha-hydroxy acids until very recently. At the end of 2007, we reported messenger RNA (mRNA)-directed polyester synthesis by using the new emerging method of genetic-code reprogramming in which alpha-hydroxy acids with various kinds of side-chains are assigned to arbitrarily chosen codons. In this work, we have achieved the ribosomal synthesis of polyesters with the sequence composition and length in a fully controlled manner according to the sequence of mRNA. This Concept article describes the background of the method development and its application to the synthesis of polyesters.

Synthesis of derivatives of imidazo[4,5-b]pyridine: Novel sulfur contained side chains for macrolide antibiotics

Two series of novel derivatives of imidazo[4,5-b]pyridine were synthesized. These compounds could be used as side chains of semisynthesised ketolide antibiotics. The side chains have free amine group which can attached to ketolide core. Macrolides with this kind of side chains will show obvious activities against erythromycin-resistant strains. The structure of the side chains was confirmed by 1H, 13C NMR, MS, HMBC spectra.

Investigation of mechanisms of formation of biphenyls and benzonaphthothiophenes by simulation experiment

The formation mechanisms of biphenyl series and benzonaphthothiophene series are investigated by means of simulation experiment. Biphenyl series are likely formed in two ways: one is the aromatization of the chain compounds containing conjugated C==C double bonds or the compounds with such a kind of sidechains, and the other is the reaction of sulfur with ordinary chain compounds, in which sulphur acts on ordinary sidechain compounds by seizing some hydrogens and forming (H 2 S and) the intermediates with conjugated C==C double bonds first, and then the intermediates are aromatized. One of the basic precursors of benzonaphthothiophenes is likely the phenylnaphthalenes which may originate from the chain compounds containing conjugated C==C double bonds, the compounds with such sidechains and saturate or unsaturate chain compounds. Thermal stability of biphenyls is high, but they can become dibenzothiophenes and polycyclic aromatic hydrocarbons or dibenzofurans and polycyclic aromatic hydrocarbons respectively in the presence of sulphur or oxygen. The ratio of biphenyl and m -biphenyl to biphenyls may be employed to indicate the depositional environment in the mild to medium maturation, of which the higher value indicates a fresh water depositional environment and the lower indicates a saline depositional environment. The relative high content of benzonaphthothiophenes in the crude oil indicates that the crude oil has undergone an intense sulfurization in the source rock or reservoir.

Association of Near-Infrared Dyes with Bovine Serum Albumin

The binding of five near-infrared (near-IR) dyes to bovine serum albumin (BSA) has been evaluated by absorption, fluorescence, and circular dichroism. These dyes have a common squarilic acid polymethine backbone but differ in the substituents on two sites, R1 and R2, symmetrically located on the chromophore. The magnitude of the association constants for the dye–albumin complexes depended on the nature of the side chains and ranged from 34,000 to 1 × 107 M−1. Listed by the kind of side chain and in increasing binding order, the association constants are: [R1 = R2 = butyl phthalimide] &lt; [R1 = R2 = cetyl] &lt; [R1 = R2 = ethyl] &lt; [R1 = butyl phthalimide, R2 = butyl sulfonate] &lt; [R1 = R2 = butyl sulfonate]. The chromophore seems to interact mainly with a hydrophobic cavity on BSA. However, the association constants increase substantially when the side chain or chains are butyl sulfonate. This observation suggests that near the hydrophobic region there is at least one positively charged site with which the butyl sulfonate chain or chains interact. The molar ratio of the dye–albumin complex determined was 1:1. The optical constants of the dye–albumin complexes cannot be determined directly; therefore, a method is described for determining these complexes' optical parameters and thus their association constants.

NMR investigations on a liquid‐crystalline side‐chain siloxane polymer with a wide biphasic region

AbstractA polysiloxane bearing two different kinds of side chains has been studied by nuclear magnetic resonance and relaxation investigations. Both side chains contain the same mesogenic core but differ in their connection to the main chain: one of them is bound directly to the backbone, the other is linked to it via a (CH2)3 spacer. In this sample, the isotropic and mesomorphic phases coexist over a relatively wide range of temperatures. We have tried to explain this phenomenon by microphase separation. For the sA –sB transition a similar biphasic behaviour could not be observed with our methods. The order parameter has been estimated selectively for carbons in different parts of the side chain (spacer, wing group, mesogenic core). The behaviour of the order parameter in the mesomorphic regions of the biphase was observed, and a possible explanation is given.

Isolation, characterization, and antitumor activities of the cell wall polysaccharides from Elsinoe leucospila.

A cell-wall preparation from the cells of Elsinoe leucospila, which produces elsinan extracellularly when grown on sucrose or glucose-potato extract medium, was fractionated systematically. The heteropolysaccharide that was released by treatment with Actinase E digestion, comprised D-mannose, D-galactose, and D-glucose (molar ratio, 1.5:1.0:0.1). Methylation, mild acid hydrolysis, and 13C-NMR studies suggested that the polysaccharide contains a backbone of alpha-(1----6)-linked D-mannose residues having two kinds of side chains, one attached at the O-4 with single or short beta-(1----6)-linked D-galactofuranosyl residues, and the other attached at O-2 with short side chains, most probably, of alpha-(1----3)-linked D-mannopyranosyl residues. A moderately branched D-glucan fraction, obtained from the cold alkali extract, was fractionated to give an antitumor-active purified beta-(1----3)-glucan having branches of single beta-D-glucosyl groups, one out of eight D-glucose residues being substituted at the O-6.

Asymmetric cyclopalladation in the ferrocene series as a tool for enantioselective synthesis. Preparation of some analogues of natural products

The previously described asymmetric cyclopalladation has been applied to the esters of 7-dimethylamino-7-ferrocenylenanthic acid, I, to afford the optically active palladium derivative, II. The absolute configuration of the chiral plane is determined by the configuration of the inductor: the acylamino acid salt. The palladium atom in II was then substituted by a σ-ketovinyl group using the reaction with pentyl vinyl ketone, to yield III. The latter substance undergoes full reduction when treated with Et 3SiH + CF 3COOH (the ionic hydrogenation reaction) resulting in the optically active prostanoic acid analogue, IV. On the other hand, III in the form of the methiodide is reduced by NaBH 4 with the elimination of the amine group and the and the formation of allyl alcohol V. This kind of side chain is characteristic of many prostaglandins. Bromination of II followed by the repeated cyclopalladation opens the way to trisubstitute derivatives. The pathway outlined provides a rapid synthesis of optically active compounds which are the ferrocene analogues of natural prostaglandins.

Chemical topography of sidechains in enzymes.

Information concerning the structure and the structural flexibility, the motility, of polypeptide chains in an enzyme may be obtained by use of the method of sidechain modification. Evaluation of such information requires a rigorous kinetic analysis of the chemical modification process. The need to restrict the study to a single residue is emphasized and illustrated with examples. It is shown that the reaction of the second reactive SH group of triosephosphatedehydrogenase with an appropriate reagent is the result of the fluctuation of the polypeptide chain in the native enzyme. A similar reaction due to the same cause is described for the reaction of the buried SH group of pancreatic amylase. The complex analysis of the carboxymethylation of aldolase, using correlated kinetic, enzymological and sequence studies, has established in the author's laboratory, the relation of a less reactive SH group to the active site. Similar considerations have been applied to the study of SH groups involved in subunit interaction within lactate dehydrogenase. In the lifetime of a generation the chemistry of proteins has made a full turn from the ignoramus et ignorabimus of the early 'twenties to the complete amino acid sequences and detailed three-dimensional models deduced from x-ray crystallography. During the development of these modern methods, chemical topography or surface chemistry of enzymes has contributed a great deal to our knowledge of the biologically important functional groups of enzymes. The rapid progress in enzyme chemistry has led to the belief that knowledge of the nature and position of all atoms in the enzyme molecule is enough to explain its biological function. Such reductionism is, in my view, not warranted. In our laboratory in Budapest we have collected in the past few years some data on the location of sidechains and on their role in biological activity. These results I should like to use to illustrate the potentialities of the method of sidechain modification in order to show in which respects chemical topography may contribute to the understanding of the biological function. Chemical modification of sidechains, and some physicochemical methods specific for one kind of sidechain, have long been used to determine which of these sidechains might be on the surface of the protein and again which of them might be involved in the mechanism of enzyme action. The scattered data obtained in this way have been the only evidence available for a long time. With

Alkyl chain branching in ethylene–vinyl acetate copolymer

AbstractEthylene–vinyl acetate copolymers contain two kinds of side chains: acetoxy branches originating from incorporated vinyl acetate and alkyl branches. The alkyl branching was determined by infrared analysis after converting the ethylene–vinyl acetate copolymer to a hydrocarbon polymer by three steps: hydrolysis, iodation with hydriodic acid containing red phosphorus, and reductive hydrogenation with lithium aluminum hydride. It was found that physical properties such as stiffness were dependent both on the degree of alkyl chain branching and on vinyl acetate content.