Exclusion Chromatography-multiangle Laser Light Research Articles

Quality Distinguish of Red Ginseng from Different Origins by HPLC–ELSD/PDA Combined with HPSEC–MALLS–RID, Focus on the Sugar-Markers

Red ginseng (RG) has been extensively utilized in Asian countries due to its pharmacological effects. For the quality evaluation of RG, small molecules, such as ginsenosides, have been widely considered as candidates of its quality markers (Q-markers), and various analytical techniques have been developed in order to identify these compounds. However, despite the efforts to analyze the hydrophobic constituents, it is worth pointing out that about 60% of the mass of RG is made of carbohydrates, including mono-, oligo- and polysaccharides. Consequently, the quality differentiation and identification of RG from the perspective of sugar-markers should be focused. High performance liquid chromatography and evaporative light scattering detector (HPLC–ELSD) method for the determination of disaccharides in RG was established. Furthermore, high performance size exclusion chromatography–multi-angle laser light scattering–refractive index detector (HPSEC–MALLS–RID) for the determination of molecular weight and high performance liquid chromatography photodiode array (HPLC–PDA) for the determination of compositional monosaccharides in RG polysaccharides were also established. HPLC–ELSD/PDA combined with HPSEC–MALLS–RID could be used to determine the contents of disaccharides, molecular weights, and compositional monosaccharides of RG polysaccharides, which could be used for quality control, and this is a new view on the sugar marker to quality differentiation of various origins of RG.

Analytical characterization of polyamide 11 used in the context of selective laser sintering: Physico-chemical correlations

Polyamide 11 is an attractive material for additive manufacturing, however, in the selective laser sintering process it is subject to significant thermally induced stress. Suitable analytical methods are necessary to indicate any changes in the material properties. In this work, thermally stressed powder samples and printed tensile bars were analyzed by size exclusion chromatography-multi angle laser light scattering and differential scanning calorimetry. Based on the molecular weight distribution, crystallization and melting temperatures, ageing states of the investigated powders can be defined and transferred to the particles of the printed components. As a result, thermal stress led to an increase in molar mass and polydispersity. Moreover, calorimetric measurements indicated a delayed nucleation process as well as a decrease in polymorphism. Additionally, polymeric material with lower polydispersity values across the tensile bars could lead to decreasing elongation at break (εB) values. For the crystallization onset temperature the opposite effect on εB was observed.

Acid hydrolysis of corn starch genotypes. I. Impact on morphological and molecular properties

With respect of the partial molecular degradation of the starch polysaccharides, the impact of the acid-thinning process on the specific starch properties of two corn genotypes was investigated. A high amylose corn (HACS) and a waxy corn (WxCS) starch were hydrolyzed using HCl in the laboratory scale slurry process (40% w/w, 30 °C). The acid concentration (0.3, 0.6 and 0.9 M) as well as the hydrolysis time (4, 10 and 20 h) were graded systematically (experimental design) and the obtained modified starch genotypes characterized comprehensively. As revealed by scanning electron micoscopy (SEM), the supramolecular structure was preserved in general, and the carbohydrate solubilization was limited to about 2–3 %. Molecularly dispersed solutions were characterized by means of size exclusion chromatography-multi angle laser light scattering-differential refractive index detection (SEC-MALS-DRI). Both acid concentration and hydrolysis time reduced the molar mass (MM) of the starch [HACS: 4.4∙106 (native)…1.2∙106 g∙mol−1 (highest degree of degradation); WxCS: 49.7∙106 (native)…6.4∙106 g∙mol−1 (highest degree of degradation)], the amylose (AM) fraction as well as the amylopectin (AP) branch chain length systematically. Perceptible differences in dependence on starch variety were ascertained and discussed. The molecular properties of the investigated acid-thinned genotypes are selectively controllable with the hydrolysis process. The relationship between modification process, starch’s molecular state, and resulting functional properties was examined in the second part of the study.

Characterization of an extracellular polysaccharide produced by a Saharan bacterium Paenibacillus tarimensis REG 0201M

The purpose of this paper is to highlight the novel molecular characteristics and rheological properties of the polysaccharide produced by a bacterium isolated from extremophilic environment (Algerian Sahara). Phenotypic and molecular characteristics of the REG 0201M bacterial strain retained for this research were studied. Extracellular polysaccharide produced by REG 0201M was purified, characterized and its production was investigated. Analysis of 16S rDNA gene sequence showed that strain REG 0201M belonged to the species Paenibacillus tarimensis. In sucrose agar medium, 1.31 g dry weight of the polysaccharide per liter was produced. Evaluation of water absorption capacity showed that this polysaccharide was able to absorb 1000 times more water than its own weight. The average molecular weight determined by high-performance size exclusion chromatography multiangle laser light scattering was 1.718 × 106 g mol−1. Analysis of the monosaccharide composition by high-performance anion exchange chromatography showed the presence of fructose (77.67%) as the main neutral sugar, followed by galactose (20.37%), arabinose (1.79%), and rhamnose (0.16%). Its global charge determined by the Zeta potential measurement was about −35.27 ± 0.66 mV. The main functional groups were elucidated by Fourier-Transform Infrared Spectroscopy while the surface morphology was resolved by scanning electron microscopy analysis. Moreover, the rheological data revealed shear thinning properties with the same general behavior of the studied polysaccharide compared to xanthan. These results show the great potential of this polysaccharide, which could help to promote its use in various industries by replacing synthetic polymers.

Therapeutic effects of polysaccharides from Anoectochilus roxburghii on type II collagen-induced arthritis in rats

Anoectochilus roxburghii, a famous Chinese herbal medicine, has been commonly used for the treatment of liver disease, diabetes, and rheumatoid arthritis. Our study aimed to investigate the anti-rheumatoid arthritis effects of A. roxburghii polysaccharides (ARP), using the rat's model of type II collagen-induced arthritis (CIA). ARP was prepared by alcohol sedimentation and structurally characterized based on combined chemical, chromatographic and spectroscopic methods. High Performance Size Exclusion Chromatography-Multiangle Laser Light Scattering-Refrative Index (HPSEC–MALLS–RI) analysis revealed that ARP includes two peaks, and the weight-average molecular weight (Mw) of the principal one was estimated as 5.90 kDa with a relative content of 98.2%. Pharmacological results exhibited that ARP significantly decreased the arthritis index and ameliorated the inflammatory cell infiltration and the synovial tissue destruction in CIA rats. Additionally, ARP possessed significant NO production inhibitory effects and antioxidant activity. Further anti-inflammatory mechanism investigations indicated that ARP significantly inhibited the activation of nuclear factor κB (NF-κB) pathway by suppressing the phosphorylation of IκB and p65, which subsequently down-regulated the mRNA expressions of IL-1β and IL-6 in LPS-stimulated RAW 264.7 cells. These findings suggested that ARP has great potential in the development of functional foods and dietary supplements for the treatment of rheumatoid arthritis.

Molar Mass Analysis of Hydrophobically Modified Hyaluronic Acid by SEC‐MALLS: Facing the Challenges of Amphiphilic Biomacromolecules

AbstractA size exclusion chromatography–multiangle laser light scattering (SEC‐MALLS) method is developed for determining the molar masses of amphiphilic hyaluronan (HA), consisting of a hydrophilic polymer backbone modified to varying extents with hydrophobic, polymerizable acrylate groups. The polymers are prepared via the base‐catalyzed esterification of HA with acrylic anhydride. Various parameters are investigated including mobile phase composition, temperature, pH, salt type, and concentration in order to find the most suitable conditions for completely dissolving the modified polymers irrespective of the degree of substitution (DS), and for suppressing secondary polymer interactions. The hydrolytic and the thermal stability of the different materials at various experimental conditions are also extensively investigated. HAs with DS varying from 0 to 3.4 are subsequently analyzed at the optimized experimental conditions for the mobile phase being DMSO/H2O 60/40(v/v) with 0.05 M LiBr and an operating temperature of 40 °C. The refractive index increments (dn/dc) of the HAs are determined and the results show a dependence of dn/dc on DS.

Alkaline dissolution of native potato starch − impact of the preparation conditions on the solution properties determined by means of SEC-MALS

The preparation of molecularly dispersed solutions of starch for the characterization by means of size exclusion chromatography–multi angle laser light scattering (SEC-MALS) was investigated. Solutions were prepared by pasting granular native potato starch using strong alkali at 25°C, neutralization and subsequent dilution in DMSO with the objective of ideally complete dissolution and simultaneously absence of molecular degradation. Process parameters such as type of alkali (KOH and NaOH), starch concentration in the alkaline dispersion (1.25 and 2.50%), dissolution time (0.5, 2, and 24 h), high shear treatment of the neutralized paste (Ultra-Turrax at 0.625 and 1.25%; speed: 11 000 and 24 000 min−1; duration: 2 and 4 min) and applying an aftertreatment following dilution to final concentration (0.125 and 0.250%; stirring) were systematically varied and impacts on SEC recovery rate and Mw of the starch examined using two experimental designs. Besides high reproducibility of the molecular data obtained, the laboratory-scale preparation method provided basically very good solutions. Most factors were significant and detailed conditions ensure that a high degree of a dissolved amount and simultaneous minimal molecular degradation were identified. Solutions containing 0.250% starch with applied aftertreatment gave best results (Mw between 40 × 106 g/mol (KOH) and 35 × 106 g/mol (NaOH); corresponding SEC recovery rates of 85% or higher). A pasting duration of 2 h was found to be sufficient for nearly complete dissolution. Including a high shear treatment, the preparation process was characterized by a compromise on the achieved solution state and accompanied molecular degradation. The investigated procedure represents a suitable alternative to current existing methods.

Preparation of Low Molecular Weight Chondroitin Sulfates, Screening of a High Anti-Complement Capacity of Low Molecular Weight Chondroitin Sulfate and Its Biological Activity Studies in Attenuating Osteoarthritis.

Chondroitin sulfate (CS) plays important roles in the complement system. However, the CS structure is complicated due to different sources and the number and positions of sulfate groups. The objective of this study was to prepare different low molecular weight chondroitin sulfates (LMWCSs) and to investigate the biological activity in anti-complement capacity. A series of LMWCSs was prepared from different sources and characterized by ultraviolet-visible (UV) spectroscopy, high-performance liquid chromatography (HPLC), size exclusion chromatography-multiangle laser light scattering (SEC-MALLS) and nuclear magnetic resonance (NMR) spectroscopy. Hemolytic, anti-complement 3 deposition capacity and cell viability assays were carried out to investigate the biological activities in vitro. The results showed that LMWCS prepared from shark cartilage with the oxidative degradation method (LMWCS-S-O) had the best anti-complement capacity. LMWCS-S-O could inhibit the alternative pathway of the complement system and protect chondrocytes from cell death. The attenuating effect of LMWCS-S-O on Osteoarthritis (OA) was investigated by destabilization of the medial meniscus (DMM) model in vivo. Functional wind-up, histological and C5b-9 analyses were used to evaluate the treatment effect on the OA model. In vivo results showed that LMWCS-S-O could attenuate OA. LMWCS-S-O with a high content of ΔDi-2,6diS and ΔDi-6S could be used for attenuating OA through regulating the complement system.

Dietary flavonoid fisetin increases abundance of high-molecular-mass hyaluronan conferring resistance to prostate oncogenesis.

We and others have shown previously that fisetin, a plant flavonoid, has therapeutic potential against many cancer types. Here, we examined the probable mechanism of its action in prostate cancer (PCa) using a global metabolomics approach. HPLC-ESI-MS analysis of tumor xenografts from fisetin-treated animals identified several metabolic targets with hyaluronan (HA) as the most affected. Efficacy of fisetin on HA was then evaluated in vitro and also in vivo in the transgenic TRAMP mouse model of PCa. Size exclusion chromatography-multiangle laser light scattering (SEC-MALS) was performed to analyze the molar mass (Mw) distribution of HA. Fisetin treatment downregulated intracellular and secreted HA levels both in vitro and in vivo Fisetin inhibited HA synthesis and degradation enzymes, which led to cessation of HA synthesis and also repressed the degradation of the available high-molecular-mass (HMM)-HA. SEC-MALS analysis of intact HA fragment size revealed that cells and animals have more abundance of HMM-HA and less of low-molecular-mass (LMM)-HA upon fisetin treatment. Elevated HA levels have been shown to be associated with disease progression in certain cancer types. Biological responses triggered by HA mainly depend on the HA polymer length where HMM-HA represses mitogenic signaling and has anti-inflammatory properties whereas LMM-HA promotes proliferation and inflammation. Similarly, Mw analysis of secreted HA fragment size revealed less HMM-HA is secreted that allowed more HMM-HA to be retained within the cells and tissues. Our findings establish that fisetin is an effective, non-toxic, potent HA synthesis inhibitor, which increases abundance of antiangiogenic HMM-HA and could be used for the management of PCa.

Ag‐nanocomposite based on carboxymethylcellulose for humidity detection: Green synthesis and sensing performances

ABSTRACTA novel highly sensitive Ag‐nanocomposite for humidity detection has been successfully prepared. Initially, cellulose isolated from Tunisian palm date petiole was converted to carboxymethyl cellulose (CMC) as biomatrix under heterogeneous conditions. The synthesized product was thoroughly characterized by means of FT‐IR spectroscopy, viscosity analysis, and high performance size exclusion chromatography multiangle laser light scattering. CMC was used as reducing and stabilizing agent to prepare CMC‐stabilized silver nanoparticles via a rapid green method. The bioreduction of silver ions under different experimental conditions, including Ag+ concentration and pH, was investigated. Optimal experimental conditions provided a long‐term stable colloidal suspension and well‐dispersed spherical shape Ag NPs with a size ranging from 13 to 28 nm. Ag‐nanocomposite coated quartz microbalance crystal was used as sensitive layer for humidity detection. A comparative study showed that the immobilized metallic nanostructures greatly reduced changes in visco‐elastic properties, increased surface area as well as surface local charge density of the CMC. Consequently, sensor performances were greatly enhanced: better stability even at higher relative humidity (RH), good reproducibility and linearity (11–98% RH), low hysteresis characteristics, and rapid response and recovery times (14 and 6 s, respectively) were obtained. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43686.

Acid-thinned corn starch-impact of modification parameters on molecular characteristics and functional properties

Acid-thinned corn starches were prepared systematically by varying acid concentrations (0.09–0.72 M HCl) and hydrolysis times (4 and 24 h). The relationships between modification parameters, molecular starch structure, and functional properties were investigated. The carbohydrate solubilization was significantly enhanced with increasing acid concentration only in the long-term process. SEM micrographs revealed the preservation of the granular structure and the thermal properties changed only moderately applying different hydrolysis conditions. Molecular characterization using SEC-MALS (size exclusion chromatography-multi angle laser light scattering) showed a strong degradation of amylopectin after 4 h of hydrolysis. Enzymatic debranching prior to the analysis and separation of the amylose peak using deconvolution enabled the calculation of MMD curves of the acid-thinned amylose fraction. The data gave evidence of extensive molecular degradation of the amylose with increasing acid concentration when hydrolyzed for 24 h. The hot paste viscosity decreased with decreasing Mw and the sol-to-gel-transition temperature was found to be strongly dependent on both, the Mw of the starch as well as the amylose fraction. The correlation between molecular properties and gel strength gave evidence of an optimum degree of hydrolysis. Acid-thinning of the starch to Mw of about 12 · 106–8 · 106 g · mol−1 and 3 · 105–2.5 · 105 g · mol−1 for the amylose fraction, respectively, resulted in the highest gel strength within the present study. However, differences in gel strength had only marginal impact on the gel elasticity. The peak separation permitted a comprehensive and detailed characterization of the amylose fraction. The obtained data proved the exposed role of the amylose in the gelation process of acid-thinned starches and their gel firmness. Correlations between the modification process, the molecular starch structure, and resulting functional properties were found.

An Intrinsically Disordered Region in the Proapoptotic ASPP2 Protein Binds to the Helicobacter pylori Oncoprotein CagA.

The leading risk factor for gastric cancer in humans is infection by Helicobacter pylori strains that express and translocate the oncoprotein CagA into host epithelial cells. Once inside host cells, CagA interacts with ASPP2, which specifically stimulates p53-mediated apoptosis and reverses its pro-apoptotic function to promote ASPP2-dependent degradation of p53. The X-ray crystal structure of a complex between the N-terminal domain of CagA and a 56-residue fragment of ASPP2, of which 22 residues were resolved, was recently described. Here, we present biochemical and biophysical analyses of the interaction between the additional regions of CagA and ASPP2 potentially involved in this interaction. Using size exclusion chromatography-multiangle laser light scattering, circular dichroism, and nuclear magnetic resonance analyses, we observed that the ASPP2 region spanning residues 331-692, which was not part of the ASPP2 fragment used for crystallization, is intrinsically disordered in its unbound state. By surface plasmon resonance analysis and isothermal titration calorimetry, we found that a portion of this disordered region in ASPP2, residues 448-692, binds to the N-terminal domain of CagA. We also measured the affinity of the complex between the ASPP2 fragment composed of residues 693-918 and inclusive of the fragment used for crystallization and CagA. Additionally, we mapped the binding regions between ASPP2 and CagA using peptide arrays, demonstrating interactions between CagA and numerous peptides distributed throughout the ASPP2 protein sequence. Our results identify previously uncharacterized regions distributed throughout the protein sequence of ASPP2 as determinants of CagA binding, providing mechanistic insight into apoptosis reprogramming by CagA and potential new drug targets for H. pylori-mediated gastric cancer.

Dimerization of matrix protein is required for budding of respiratory syncytial virus.

Respiratory syncytial virus (RSV) infects epithelial cells of the respiratory tract and is a major cause of bronchiolitis and pneumonia in children and the elderly. The virus assembles and buds through the plasma membrane, forming elongated membrane filaments, but details of how this happens remain obscure. Oligomerization of the matrix protein (M) is a key step in the process of assembly and infectious virus production. In addition, it was suggested to affect the conformation of the fusion protein, the major current target for RSV antivirals, in the mature virus. The structure and assembly of M are thus key parameters in the RSV antiviral development strategy. The structure of RSV M was previously published as a monomer. Other paramyxovirus M proteins have been shown to dimerize, and biochemical data suggest that RSV M also dimerizes. Here, using size exclusion chromatography-multiangle laser light scattering, we show that the protein is dimeric in solution. We also crystallized M in two crystal forms and show that it assembles into equivalent dimers in both lattices. Dimerization interface mutations destabilize the M dimer in vitro. To assess the biological relevance of dimerization, we used confocal imaging to show that dimerization interface mutants of M fail to assemble into viral filaments on the plasma membrane. Additionally, budding and release of virus-like particles are prevented in M mutants that fail to form filaments. Importantly, we show that M is biologically active as a dimer and that the switch from M dimers to higher-order oligomers triggers viral filament assembly and virus production. Human respiratory syncytial virus (RSV) is the most frequent cause of infantile bronchiolitis and pneumonia. The enormous burden of RSV makes it a major unmet target for a vaccine and antiviral drug therapy. Oligomerization of the matrix protein is a key step in the process of assembly and production of infectious virus, but the molecular mechanism of RSV assembly is still poorly understood. Here we show that the RSV matrix protein forms dimers in solution and in crystals; the dimer is essential for formation of higher-order oligomers. Destabilizing the dimer interface resulted in the loss of RSV filament formation and a lack of budding of virus-like particles. Importantly, our findings can potentially lead to new structure-based RSV inhibitors targeting the assembly process.

Structural characteristics and hypoglycemic activity of polysaccharides from Coprinus comatus

Abstract The effects of grinding process on the extraction of polysaccharide from Coprinus comatus were investigated. The extracts named as CCPF and CCPP were obtained from the fragments and the powder of the C. comatus fruiting bodies, respectively. The comparison on the chemical analysis of CCPF and CCPP showed that reducing particle size could dramatically improve the extract yield and content of polysaccharide fractions, which resulted from the increasing of high molecular weight (Mw) fractions. The high Mw fraction CCPP-1 was isolated using the ethanol precipitating method. Its molecular weight was estimated to be 2.44×107 g/mol by high-performance size exclusion chromatography-multi angle laser light scattering (HPSEC-MALLS). CCPP-1 took compact conformation in aqueous solution. Structural analysis showed that CCPP-1 was α- d -(1→4)-glucan with branches at C-6 consisting of non-reducing terminal approximately every fourteen residues. The hypoglycemic activity study revealed that CCPP-1 had no effect on reducing blood sugar. The crude polysaccharide extracts CCPF showed significant hypoglycemic activity.

Structure and molar mass analysis of pneumococcal capsular polysaccharides by 1H NMR and HPSEC-MALLS

Objective To analyze the structures and molecular weight distributions of the capsular polysaccharides from 6 serotypes of pneumococcus .Methods The structures of pneumococcal capsular pol-ysaccharides of 6 serotypes were analyzed by 1 H nuclear magnetic resonance （ NMR） .Chemical shifts of all characteristic protons were investigated to analyze polysaccharide integrity and inter -assay consistency .High performance size exclusion chromatography-multi angle laser light scattering （ HPSEC-MALLS） was used to measure the molecular weights .Results The chemical shifts of all characteristic protons of the pneumococ-cal capsular polysaccharides of 6 serotypes were consistent with the standard chemical shift .The weight-aver-age molecular mass of the pneumococcal capsular polysaccharides ranged from 7.182×104 g/mol（for serotype 19A） to 1.273×106 g/mol（for serotype 9V）examined by HPSEC-MALLS.Conclusion The structures and molecular weight distributions of pneumococcal capsular polysaccharides could be rapidly and effectively ana -lyzed by 1 H NMR and HPSEC-MALLS.Moreover, C-PS and acetate contained in capsular polysaccharides could also be detected .HPSEC-MALLS is an applicable method for the quantitative analysis of molar mass distributions in different serotypes of pneumococcal capsular polysaccharides . Although 1 H NMR and HPSEC-MALLS have been accepted as the quality control measurements by WHO , to use them as the re-placements of the traditional QC method still needs further investigation . Key words: Pneumococcal capsular polysaccharide; 1 H NMR; Chemical structure; HPSEC-MALLS; Weight-average molecular mass

Structure of glycoproteins from Acacia gum: An assembly of ring-like glycoproteins modules

The glycoprotein (GP) molecular fraction structure of the gum exudate of Acacia senegal (gum Arabic) isolated from hydrophobic interaction chromatography was investigated using high-performance size exclusion chromatography–multi angle laser light scattering (HPSEC–MALLS), small angle X-ray scattering (SAXS), synchrotron radiation circular dichroism (SRCD) and transmission electron microscopy (TEM) observations. In solution, GP would be a mixture of spheroidal monomers and more anisotropic oligomers as suggested by the two exponent values found in the Rg vs. Mw relationship and TEM observations. The GP conformation probed by SAXS was ascribed to a thin object with a triaxial ellipsoid morphology, certainly attributed to GP oligomers. A 9nm diameter particle was also identified by SAXS in agreement with the dimensions identified by TEM on single isolated ring-like structures. The GP oligomerization process, as probed by TEM, would be the result of ring-like subunits self-association. This self-association would lead to more linear or, sometimes, cyclised assembly. At the molecular level, GP fraction was found to have secondary structures mainly made of β-sheets and turns (64%) but also, to a lesser extent, made of polyproline II (PPII) and α-helices (19%). These features were characteristic of hydroxyprolin-rich glycoproteins with arabinosylated and arabinogalactan polysaccharide side chains grafted to the polypeptide backbone. The GP molecular fraction structure from Acacia gum would be an assembly of ring-like glycoproteins modules. These ring-like structures were certainly due to hydroxyproline (Hyp)–arabinogalactan (AG) subunits.

Characterization of Exopolysaccharides Produced by Bifidobacterium longum NB667 and Its Cholate-Resistant Derivative Strain IPLA B667dCo

Bifidobacteria are natural members of the human intestinal microbiota and some strains are being used as probiotics. Adaptation to bile can allow them to increase survival in gastrointestinal conditions, thus improving their viability. Bifidobacterium longum NB667 and the cholate-resistant strain B. longum IPLA B667dCo produced exopolysaccharides (EPS) that were partially characterized. Analysis by size exclusion chromatography-multiangle laser light scattering indicated that the EPS crude fractions of both strains contained two polymer peaks of different molar mass. On the basis of chromatographic techniques both peaks appeared to be heteropolysaccharides. The smaller peak was mainly composed of glucose, galactose and rhamnose whose molar ratios and linkage types showed slight variations between the EPS fractions of both strains. The bigger peak consisted of glucose and galactose; the monosaccharide composition was identical in the EPS fractions of the two microorganisms, but their infrared spectra presented some differences regarding compounds other than carbohydrates that seem to be associated to the polymer. Differences in the composition of EPS fractions did not affect the capability of crude EPS from B. longum to be fermented by the human intestinal microbiota in fecal batch cultures.

Comb-shaped graft copolymers with cellulose side-chains prepared via click chemistry

Abstract Comb-shaped copolymers with cellobiose acetate or cellulose triacetate (CTA) side-chains, PPMA-g-(CTA2-C15) and PPMA-g-(CTA13-C15), were prepared by grafting N-(15-azidopentadecanoyl)-2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β- d -glucopyranosyl)-β- d -glucopyranosylamine (CTA2-C15-N3) and N-(15-azidopentadecanoyl)-tri-O-acetyl-β-cellulosylamine (CTA13-C15-N3, number average degree of polymerization (DPn) = 13) onto poly(2-propyn-1-yl methacrylate) (PPMA, weight average degree of polymerization (DPw, X + Y = 5.59 × 102)) via “click chemistry”. The copolymers were characterized by 1H, 13C and two-dimensional NMR and size exclusion chromatography–multi-angle laser light scattering (SEC–MALS) measurements. The numbers of CTA side-chains (X) of PPMA-g-(CTA2-C15) and PPMA-g-(CTA13-C15) were calculated as 4.03 × 102 and 2.45 × 102, respectively. Copolymers with cellulosic side-chains, PPMA-g-(CELL2-C15) and PPMA-g-(CELL13-C15), were successfully obtained after deacetylation of PPMA-g-(CTA2-C15) and PPMA-g-(CTA13-C15), respectively. X-ray diffraction measurements revealed that PPMA-g-(CELL13-C15) showed crystalline pattern of cellulose II, which is believed to have anti-parallel orientation.

Compared molecular characterization of hyaluronan using multiple-detection techniques

The biological functions as well as physico-chemical properties of hyaluronan (HA), one of the most important and ubiquitous glycosaminoglycan in various organisms, are closely related to its molecular weight, molecular weight distribution and chain conformation. For this reason it is crucially important to make a reliable characterization of these parameters for HA in both chemical and clinical fields. The present work compared the application of different techniques including capillary viscometry, concentration gradient multiangle laser light scattering (CG-MALLS), size exclusion chromatography-multiangle laser light scattering (SEC-MALLS), asymmetric flow field flow fractionation-multiangle laser light scattering (AFlFFF-MALLS) and horizontal agarose gel electrophoresis (AGE), to the characterization of a range of HA samples of bacterial and animal sources. The advantage and limitation of these techniques were discussed in terms of producing accurate and reliable molecular parameters.

Effect of nucleating agents on the molar mass distribution and its correlation with the isothermal crystallization behavior of poly(L‐lactic acid)

AbstractIn this work, the effect of the processing conditions on the thermal behavior of a commercial poly(L‐lactic acid) (PLLA) was investigated. In particular, PLLA having a very high molecular weight was processed by a discontinuous mixer at different mixing conditions. The molar mass variation was investigated by size exclusion chromatography–multiangle laser light scattering chromatography, and the thermal characteristics were detected by the conventional differential scanning calorimetry and dynamic mechanical thermal analysis. Tensile tests were performed at room temperature and at 60°C. Our attention was essentially focused on the crystallization behavior of the various samples obtained. A modest decline in the molar mass was obtained with two mixing temperatures of 210 and 250°C, but a significant increase in the crystalline phase content was noticed, with a concomitant tremendous increment in the crystallization rate. A correlation was also made between the molar mass distribution and crystallization rate in isothermal conditions, where clearly visible were the effects of the processing temperature on both the molar mass distribution and how the nucleating agents affected the crystallinity of PLLA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011