Degree Of Branching Research Articles

Growth response to nitrate enrichment helps facilitate success of an alien Potamogeton in New Zealand streams

Motivated by stream ecosystem degradation by eutrophication, we mimicked slow flowing lowland stream conditions with a novel experimental setup to further our understanding of aquatic plant responses to increases in nitrate and light. We conducted a mesocosm growth experiment of two species from the genus Potamogeton: P. crispus (alien) and P. ochreatus (native), grown at four nitrate and four light levels. We hypothesised that (i) internal nutrient status of the plants would scale with water column nutrient concentration, and that (ii) plant performance would reflect the nutrient status of the plant. Furthermore, we hypothesised that (iii) a low irradiance level would negate the effects of an increased nitrate level. In relation to (ii) we hypothesised that (iv) the traits of the alien species would enable it to outperform the native species where both the availability of light and nutrient resources was high. Internal tissue N content was broadly similar in the two higher (>250 μg NO3− L−1) and the two lower nutrient treatments (<20 μg NO3− L−1) in both species and plants were therefore collapsed into high and low N-groups. High-N individuals had higher growth rates than low-N ones regardless of species or light treatment and plants had reduced growth rates at the lowest light treatment, however this response was less evident for P. crispus. The highest growth rate was found at the high-N individuals of P. crispus at the highest light treatment, and correspondingly, in this treatment this species exhibited an increase in branching degree and lateral spread from the low-N plants. As P. crispus spreads by fragmentation, our results show it to be a highly effective competitor in anthropogenically impacted areas compared to its native counterpart. Our study exemplifies how light can influence eutrophication responses of plants and how both need to be accounted for in management decisions.

Effect of modification by maltogenic amylase and branching enzyme on the structural and physicochemical properties of sweet potato starch

Sweet potato starch (SPSt) was treated sequentially with the combination of maltogenic amylase (MA) and branching enzyme (BE) (MA → BE) or BE and MA (BE→MA) to modify its structural and physicochemical properties. Following the MA → BE and BE→MA modifications, the degree of branching was increased from 12.02 % to 44.06 %; whereas, the average chain length (ACL) decreased from 18.02 to 12.32. Fourier-transform infrared spectroscopy and digestive performance analysis indicated that the modifications reduced hydrogen bonds and increased resistant starch in SPSt. Rheological analysis revealed that the storage and loss moduli of the modified samples were lower than those of the control samples, except for starch treated with MA alone. X-ray diffraction measurements suggested that the re-crystallisation peak intensities of the enzyme-modified starches were lower than those of the untreated sample. The retrogradation resistance ability of the analysed samples followed the order: BE→MA-starches > MA → BE-starches > untreated starch. The relationship between the crystallisation rate constant and short branched chains (DP6–9) was well described by linear regression. This study provides a theoretical foundation for retarding the retrogradation of starch, which can improve food quality and extend the shelf-life of enzymatically modified starchy foods.

Changes in the structure of polysaccharides under different extraction methods

Changes in the structure of polysaccharides under different extraction methods

Mixed-mode fracture model to quantify local toughness in nacre-like alumina

With the progress of ceramic engineering, tough technical ceramics such as nacre-like alumina now exhibit complex fracture patterns with high degrees of deflection, branching and bridging. If these mechanisms highly contribute to improving crack resistance, the crack geometries go beyond the hypotheses assumed in standard techniques to quantify toughness, making it difficult to understand the mechanisms responsible for crack propagation. We report a robust local solution based on a combination of analytical formulas and finite element analysis to accurately estimate the effective stress intensity factors at the tips of multiple deflected cracks. The influence of sample size on local R-curves is analysed and shown to be less important relative to standard methods. We use this method to evaluate the direct influence of zirconia nanoparticles in the nacre-like structure and highlight the role of these findings in the understanding of mechanical response and future optimisation of highly textured tough ceramics.

Remarkable improvement in the storage stability of maltodextrin through 1,4-α-glucan branching enzyme modification

Enzymatic modification is a potential approach to effectively improve the stability of maltodextrin for food and industrial applications. In this study, a 1,4-α-glucan branching enzyme from Rhodothermus obamensis STB05 (Ro-GBE) was used to modify maltodextrin. The transparency of the Ro-GBE-modified maltodextrin prepared under the optimal modification conditions: enzyme dosage of 100 U/g, reacting time of 12 h at 55 °C, and pH of 7.0, was maintained above 90% for over 30 days. In addition, the viscosity stability, retrogradation property, and freeze–thaw stability were significantly improved. Because of the constant value of the dextrose equivalent (DE), increase in α-1,6-glycosidic linkage ratio, and decrease in weight-average molecular mass (Mw), we believed that the glycosidic bond rearrangement played a vital role in the Ro-GBE modification. Moreover, Ro-GBE exhibited high specificity in cleaving long chains with DP ≥ 15 and transferring the released chains as exterior chains to form a short-clustered structure. Pearson correlation analysis revealed that the transparency stability of maltodextrin mainly correlated with the branching degree, while the viscosity stability, retrogradation property, and freeze–thaw stability mainly contributed to the Mw of branched molecules.

A New Optimization Strategy of Highly Branched Poly(β-Amino Ester) for Enhanced Gene Delivery: Removal of Small Molecular Weight Components

Highly branched poly(β-amino ester) (HPAE) has become one of the most promising non-viral gene delivery vector candidates. When compared to other gene delivery vectors, HPAE has a broad molecular weight distribution (MWD). Despite significant efforts to optimize HPAE targeting enhanced gene delivery, the effect of different molecular weight (MW) components on transfection has rarely been studied. In this work, a new structural optimization strategy was proposed targeting enhanced HPAE gene transfection. A series of HPAE with different MW components was obtained through a stepwise precipitation approach and applied to plasmid DNA delivery. It was demonstrated that the removal of small MW components from the original HPAE structure could significantly enhance its transfection performance (e.g., GFP expression increased 7 folds at w/w of 10/1). The universality of this strategy was proven by extending it to varying HPAE systems with different MWs and different branching degrees, where the transfection performance exhibited an even magnitude enhancement after removing small MW portions. This work opened a new avenue for developing high-efficiency HPAE gene delivery vectors and provided new insights into the understanding of the HPAE structure-property relationship, which would facilitate the translation of HPAEs in gene therapy clinical applications.

Synthesis and Self-Assembly of Hyperbranched Multiarm Copolymer Lysozyme Conjugates Based on Light-Induced Metal-Free Atrp

In recent years, the coupling of structurally and functionally controllable polymers with biologically active protein materials to obtain polymer-protein conjugates with excellent overall properties and good biocompatibility has been important research in the field of polymers. In this study, the hyperbranched polymer hP(DEGMA-co-OEGMA) was first prepared by combining self-condensation vinyl polymerization (SCVP) with photo-induced metal-free atom transfer radical polymerization (ATRP), with 2-(2-bromo-2-methylpropanoyloxy) ethyl methacrylate (BMA) as inimer, and Di (ethylene glycol) methyl ether methacrylate (DEGMA) and (oligoethylene glycol) methacrylate (OEGMA, Mn = 300) as the copolymer monomer. Then, hP(DEGMA-co-OEGMA) was used as a macroinitiator to continue the polymerization of a segment of pyridyl disulfide ethyl methacrylate (DSMA) monomer to obtain the hyperbranched multiarm copolymers hP(DEGMA-co-OEGMA)-star-PDSMA. Finally, the lysozyme with sulfhydryl groups was affixed to the hyperbranched multiarm copolymers by the exchange reaction between sulfhydryl groups and disulfide bonds to obtain the copolymer protein conjugates hP(DEGMA-co-OEGMA)-star-PLZ. Three hyperbranched multiarm copolymers with relatively close molecular weights but different degrees of branching were prepared, and all three conjugates could self-assemble to form nanoscale vesicle assemblies with narrow dispersion. The biological activity and secondary structure of lysozyme on the assemblies remained essentially unchanged.

Modular Principle for Complex Disordered Tetrahedral Frameworks in Quenched High-Pressure Phases of Phosphorus Oxide Nitrides.

The crystal structures of the new phosphorus oxide nitrides P40 O31 N46 and P74 O59 N84 , which were synthesized from amorphous phosphorus oxide nitride imide, exhibit complex frameworks built up from P(O,N)4 tetrahedra. The latter form various chain-like building units with various degrees of branching. These modular units can be combined and arranged in different ways, which leads to closely related structures and several disordered configurations in each compound. As the material was obtained by high-pressure high-temperature synthesis, the disorder is most likely a consequence of quenching a high-pressure phase with P(O,N)5 trigonal bipyramids. Under ambient conditions, P atoms are expected to relax by moving to the centers of the face-sharing tetrahedra that constitute the bipyramid. Diffraction patterns acquired with microfocused synchrotron radiation reveal that domains of both compounds are intergrown with H3 P8 O8 N9 , whose tetrahedral framework represents a cutout of the structures of both P40 O31 N46 and P74 O59 N84 . Powder diffraction patterns do not indicate any further phases.

Arabinoxylan of varied structural features distinctively affects the functional and in vitro digestibility of wheat starch

This study explored the effects of wheat bran arabinoxylan (AX) of various molecular structures on the functional and in vitro digestibility of wheat starch. AX was separated with sequential ethanol precipitation into different fractions (L-Fra and H-Fra), followed by acidic treatment at varied time to convert L-Fra into different subfractions (H-Sub, M-Sub and L-Sub), and the structural features of AX and its subsequent fractions were compared. The Mw and branching degree of the fractions were decreased in the order of H-Fra (545 kDa, 1.15), L-Fra (86 kDa, 0.35), H-Sub (38 kDa, 0.16), M-Sub (21 kDa, 0.10) and L-Sub (7 kDa, 0.08). The functional properties, such as pasting properties, rheological properties, thermal properties, and their effect on the in vitro digestibility of wheat starch-AX combinations, were closely related to the molecular structures of AX. AX with higher Mw, higher branching degree and phenolic content could better inhibit the starch gelatinization and retrogradation, thus reducing the apparent viscosity and gelling properties of wheat starch. The possible mechanisms can be illustrated as 1) AX could compete for water with starch to inhibit granule expansion; 2) AX could not only adsorb on the surface of starch granules through hydrogen bonds but also entangle with the leached amylose and wrap on the surface of granules; 3) AX contained phenols, leading them to inhibit granule expansion through non-covalent interactions with starch molecules. Overall, this study provides a theoretical basis to improve the quality of wheat starch foods and extend the shelf life of wheat foods.

Size selectivity in adsorption of polydisperse starches on activated carbon

The influence of molecular weight, polydispersity, and degree of branching of four potato starches (Paselli MD10, Eliane MD6, Eliane MD2, and highly branched starch) on the adsorption rates on activated carbon (Norit CA1) was investigated. Changes in starch concentration and size distribution over time were analysed by Total Starch Assay and Size Exclusion Chromatography. Average molecular weight and degree of branching of a starch scaled negatively with average adsorption rate. Within a size-distribution, adsorption rates scaled negatively with increasing molecule size, resulting in an increased average molecular weight in solution of between 25 % and 213 % and a decreased polydispersity of between 13 % and 38 %. Simulation with dummy distributions estimated the ratio of adsorption rates for 20th percentile and 80th percentile molecules within a distribution to range between a factor 4 and 8 for the different starches. Competitive adsorption decreased the adsorption rate of molecules above the average size within a sample distribution.

Study on the kinetic analysis and pyrolysis evolution in transition zone of metal salt catalyzed steam injection in-situ maoming oil shale upgrading

In order to study the kinetic characteristics and pyrolysis evolution in the transition zone of oil shale during metal salt catalyzed steam in-situ production, the oil shale and semi-cokes under different heating conditions were studied by using a self-made reactor and various analysis methods. The results show that the pyrolysis temperature of semi-cokes in the transition zone increases gradually from front to back, the mass loss in the front is greater than that in the back, and the activation energy is less than that in the back. Compared with conventional and steam heating, metal salt catalyzed steam heating enlarges the activation energy difference between the front and back of the transition zone. With the increase in pyrolysis temperature, the aliphatic content in the transition zone decreased rapidly. The front of the transition zone is the main oil and gas generation area, and the oil and gas generation potential in the back is significantly reduced. Metal salt catalyzed steam heating accelerates the pyrolysis and release of aliphatic groups and reduces the degree of aliphatic branching in the transition zone. During the initial pyrolysis, the oxygen-containing functional groups and aromatic structures in the transition zone decreased, and then increased with the increase of pyrolysis temperature. The content of oxygen-containing functional groups in the transition zone of metal salt catalyzed steam heating is generally higher than that of conventional and steam heating, while the content of aromatic structures is generally low, indicating that their interaction increases the oxidation effect, promotes the pyrolysis and release of aromatic structures, and inhibits the condensation of aromatic structures. In the presence of potassium feldspar, the high temperature accelerates the illitization of kaolinite in oil shale, and there is basically no potassium feldspar and pyrite in the back of the transition zone. Compared with metal salt catalysts and steam, temperature is the most important factor affecting the pyrolysis of inorganic minerals in oil shale and semi-cokes.

Deciphering the structural and functional characteristics of an innovative small cluster branched α–glucan produced by sequential enzymatic synthesis

Highly branched α–glucan (HBAG) proved to be a promising material as an osmotic agent in peritoneal dialysis solutions. However, high resistance of HBAG to amylolytic enzymes might be a potential drawback for peritoneal dialysis due to its high degree of branching (20–30 %). To address this issue, we designed a small–clustered α–glucan (SCAG) with a relatively low molecular weight (Mw) and limited branching. Structural characteristics revealed that SCAG was successfully synthesized by modifying waxy rice starch (WRS) using sequential maltogenic α–amylase (MA) and starch branching enzyme (BE). The Mw of SCAG was 1.40 × 105 Da, and its (α1 → 6) bonds ratio was 8.93 %, which was below that of HBAG. A relatively short branch distribution was observed in SCAG (CL = 6.27). Short–range orderliness of WRS was reduced from 0.749 to 0.322 with the MABE incubation. Additionally, SCAG had an extremely low viscosity (~12 cP) and nearly no retrogradation. Although the resistance of SCAG to amylolytic enzymes was enhanced by 15.22 % compared with native WRS, the extent was significantly lower than that of HBAG in previous studies. These new findings demonstrate the potential of SCAG as a novel functional α–glucan in food and pharmaceutical applications.

An investigation into structural properties and stability of debranched starch-lycopene inclusion complexes with different branching degrees

Debranched starch (DBS) has great probability as carrier for bioactive ingredients, but effects of branching degree (DB) on the complex formation of starch remain unclear. This study investigated the potential of DBS with different DB to load lycopene and characterized the structural properties of inclusion complexes. Glutinous rice starch was debranched to get DBS with different molecular weights, where DBS with a branching degree of 11.42 % had the greatest encapsulation efficiency (64.81 %). SEM, particle size, and zeta-potential results showed that the complexes form stable spherical crystals through electrostatic interactions. The structures of complexes were resolved by FTIR, XRD, TGA, and 13C CP/MAS NMR analytical techniques, indicating that lycopene can be loaded on DBS by the self-assembly through hydrophobic and hydrogen bonding interactions. Degradation experiments revealed that retention of complexes was significantly higher than the unencapsulated one. Our study reveals the structural features of the complex between DBS and lycopene, providing theoretical guidance for developing and producing novel nutraceuticals.

Efficient Accumulation of Amylopectin and Its Molecular Mechanism in the Submerged Duckweed Mutant.

Large-scale use of fossil fuels has brought about increasingly serious problems of environmental pollution, development and utilization of renewable energy is one of the effective solutions. Duckweed has the advantages of fast growth, high starch content and no occupation of arable land, so it is a promising starchy energy plant. A new submerged duckweed mutant (sub-1) with abundant starch accumulation was obtained, whose content of amylopectin accounts for 84.04% of the starch granules. Compared with the wild type (Lemna aequinoctialis), the branching degree of starch in sub-1 mutant was significantly increased by 19.6%. Chain length DP 6-12, DP 25-36 and DP > 36 of amylopectin significantly decreased, while chain length DP 13-24 significantly increased. Average chain length of wild-type and sub-1 mutant starches were greater than DP 22. Moreover, the crystal structure and physical properties of starch have changed markedly in sub-1 mutant. For example, the starch crystallinity of sub-1 mutant was only 8.94%, while that of wild-type was 22.3%. Compared with wild type, water solubility of starch was significantly reduced by 29.42%, whereas swelling power significantly increased by 97.07% in sub-1 mutant. In order to further analyze the molecular mechanism of efficient accumulation of amylopectin in sub-1 mutant, metabolome and transcriptome were performed. The results showed that glucose accumulated in sub-1 mutant, then degradation of starch to glucose mainly depends on α-amylase. At night, the down-regulated β-amylase gene resulted in the inhibition of starch degradation. The starch and sucrose metabolism pathways were significantly enriched. Up-regulated expression of SUS, AGPase2, AGPase3, PYG, GPI and GYS provide sufficient substrate for starch synthesis in sub-1 mutant. From the 0H to 16H light treatment, granule-bound starch synthase (GBSS1) gene was inhibited, on the contrary, the starch branching enzyme (SBE) gene was induced. Differential expression of GBSS1 and SBE may be an important reason for the decrease ratio of amylose/amylopectin in sub-1 mutant. Taken together, our results indicated that the sub-1 mutant can accumulate the amylopectin efficiently, potentially through altering the differential expression of AGPase, GBSS1, SBE, and BAM. This study also provides theoretical guidance for creating crop germplasm with high amylopectin by means of synthetic biology in the future.

Tailoring structural, rheological and gelling properties of watermelon rind pectin by enzymatic treatments

In this work, pectin extracts from watermelon rind (WRP) were enzymatically treated to evaluate their potential for preparing hydrogels with the addition of CaCl 2 . Based on a previous work, two different conditions were selected to obtain WRP extracts according to the 1) highest yield (OP) or 2) highest yield without negatively affecting the branching and native structure of pectin (OPA). Firstly, both WRP extracts were enzymatically modified using different treatments (de-esterification and/or de-branching of galacturonic and arabinose side chains, and deproteinization), and their impact on the esterification degree, monosaccharide composition and changes on their structural properties (linearity and branching degree) were deeply analysed. Then, the effect of the structural properties of the resulting pectin on the rheological behaviour and nanostructure of the hydrogels was investigated. The presence of long branched side chains and high methyl-esterified galacturonic acid chains promoted the formation of weaker hydrogels whereas de-esterification of the original pectin enabled intermolecular association giving rise to stronger hydrogels with the formation of ordered and densely packed structures (as deduced from SAXS results). However, the presence of small arabinogalactans side chains in the de-branched and de-esterified pectin extracts acted as reinforcement agents, inducing the formation of more densely packed networks and stronger hydrogels than their less-branched counterpart. These results demonstrated the impact of the pectin structure on the hydrogel-forming capacity. • Two watermelon rind pectin extracts were enzymatically modified. • Enzymes acting on neutral sugar side chains did not significantly de-branch the pectin structure. • Weaker gels were obtained when pectins were treated with de-branching enzymes. • Stronger gels were produced when pectin was de-esterified. • The strongest gels were produced when de-esterification and de-branching enzymes were combined.

Implicit-Solvent Coarse-Grained Simulations of Linear-Dendritic Block Copolymer Micelles.

The design of nanoassemblies can be conveniently achieved by tuning the strength of the hydrophobic interactions of block copolymers in selective solvents. These block copolymer micelles form supramolecular aggregates, which have attracted great attention in the area of drug delivery and imaging in biomedicine due to their easy-to-tune properties and straightforward large-scale production. In the present work, we have investigated the micellization process of linear-dendritic block copolymers in order to elucidate the effect of branching on the micellar properties. We focus on block copolymers formed by linear hydrophobic blocks attached to either dendritic neutral or charged hydrophilic blocks. We have implemented a simple protocol for determining the equilibrium micellar size, which permits the study of linear-dendritic block copolymers in a wide range of block morphologies in an efficient and parallelizable manner. We have explored the impact of different topological and charge properties of the hydrophilic blocks on the equilibrium micellar properties and compared them to predictions from self-consistent field theory and scaling theory. We have found that, at higher degrees of branching in the corona and for short polymer chains, excluded volume interactions strongly influence the micellar aggregation as well as their effective charge.

Resistant Starch but Not Enzymatically Modified Waxy Maize Delays Development of Diabetes in Zucker Diabetic Fatty Rats

Background The incidence of type 2 diabetes (T2D) is increasing worldwide, and nutritional management of circulating glucose may be a strategic tool in the prevention of T2D.Objective We studied whether enzymatically modified waxy maize with an increased degree of branching delayed the onset of diabetes in male Zucker diabetic fatty (ZDF) rats.Methods Forty-eight male ZDF rats, aged 5 wk, were divided into 4 groups and fed experimental diets for 9 wk that contained 52.95% starch: gelatinized corn starch (S), glucidex (GLU), resistant starch (RS), or enzymatically modified starch (EMS). Blood glucose after feed deprivation was assessed every second week; blood samples taken at run-in and at the end of the experiment were analyzed for glycated hemoglobin (HbA1c) and plasma glucose, insulin, and lipids. During weeks 2 and 8, urine was collected for metabolomic analysis.Results Based on blood glucose concentrations in feed-deprived rats, none of the groups developed diabetes. However, in week 9, plasma glucose after feed deprivation was significantly lower in rats fed the S and RS diets (13.5 mmol/L) than in rats fed the GLU and EMS diets (17.0–18.9 mmol/L), and rats fed RS had lower HbA1c (4.9%) than rats fed the S, GLU, and EMS (5.6–6.1%) diets. The homeostasis model assessment of insulin resistance was significantly lower in rats fed RS than in rats fed the other diets (185 compared with 311–360), indicating that rats fed the S, GLU, and EMS diets were diabetic, and a 100% higher urine excretion during week 8 in rats fed the GLU and EMS diets than that of rats fed S and RS showed that they were diabetic. Urinary nontargeted metabolomics revealed that the diabetic state of rats fed S, GLU, and EMS diets influenced microbial metabolism, as well as amino acid, lipid, and vitamin metabolism.Conclusions EMS did not delay the onset of diabetes in ZDF rats, whereas rats fed RS showed no signs of diabetes.

Visible‐Light‐Mediated Controlled Radical Branching Polymerization in Water

AbstractHyperbranched polymethacrylates were synthesized by green‐light‐induced atom transfer radical polymerization (ATRP) under biologically relevant conditions in the open air. Sodium 2‐bromoacrylate (SBA) was prepared in situ from commercially available 2‐bromoacrylic acid and used as a water‐soluble inibramer to induce branching during the copolymerization of methacrylate monomers. As a result, well‐defined branched polymethacrylates were obtained in less than 30 min with predetermined molecular weights (36 000&lt;Mn&lt;170 000), tunable degree of branching, and low dispersity values (1.14≤Đ≤1.33). Moreover, the use of SBA inibramer enabled the synthesis of bioconjugates with a well‐controlled branched architecture.

Visible-Light-Mediated Controlled Radical Branching Polymerization in Water.

Hyperbranched polymethacrylates were synthesized by green-light-induced atom transfer radical polymerization (ATRP) under biologically relevant conditions in the open air. Sodium 2-bromoacrylate (SBA) was prepared in situ from commercially available 2-bromoacrylic acid and used as a water-soluble inibramer to induce branching during the copolymerization of methacrylate monomers. As a result, well-defined branched polymethacrylates were obtained in less than 30 min with predetermined molecular weights (36 000 ˂ Mn ˂ 170 000), tunable degree of branching, and low dispersity values (1.14 ≤ Đ ≤ 1.33). Moreover, the use of SBA inibramer enabled the synthesis of bioconjugates with a well-controlled branched architecture.

Involvement of branched RG-I pectin with hemicellulose in cell–cell adhesion of tomato during fruit softening

Cell adhesion of four cultivars of tomato fruit, “Micro Tom (MT)”, “Heinz 1706 (H1706)”, “Money Maker (MM)”, “Ailsa Craig (AC)” were evaluated and cell walls were analyzed in order to assess the possible contribution of pectic and hemicellulosic polysaccharides to the softening and altered cell adhesion at two different stages of ripeness. Cell wall material (CWM) and solubilised fractions of green and red ripe fruit were analyzed by chemical, enzymatic techniques. In comparison with the four cultivars of tomato fruits, H1706 and MM are harder than MT and AC at both green and red ripe stage. The ripening-associated solubilisation of rhamnogalacturonan-riched pectic polysaccharides was reduced in H1706 and MM, and the content of side -chain sugars from RG-I reduced by more than 50% in MT and AC. In addition to recognized pectic modifying enzymes, RGase had a good effect on cell separation of H1706 and MM fruit at red ripe stage. The higher RG-I content and branching degree have been associated with increased cell adhesion and reduced cell wall porosity, thus maintained fruit firmness.