Terms Of Molecular Weight Distribution Research Articles

Effect of hydrophobic property on antibacterial activities of green tea polysaccharide conjugates against Escherichia coli

We previously found that green tea polysaccharide conjugates (gTPCs) have antibacterial activity against Escherichia coli. In this study, the effect of hydrophobic property on the antibacterial activities of gTPCs was evaluated to elucidate their property-activity relationship. Three gTPCs (gTPCs-5 h, gTPCs-12 h and gTPCs-24 h) were extracted from green tea with the ethanol precipitation time of 5 h, 12 h and 24 h, respectively. These three gTPCs did not differ significantly in terms of molecular weight distribution, amino acids composition and zeta potentials. Fourier transform infrared spectroscopy results revealed that gTPCs-5 h and gTPCs-12 h processed more hydrogen bonds than gTPCs-24 h. The surface hydrophobicity and contact angle of gTPCs-5 h were larger than that of gTPCs-12 h and gTPCs-24 h. The antibacterial activity of gTPCs against E. coli decreased in the order of gTPCs-5 h > gTPCs-12 h > gTPCs-24 h. There wasn't significant difference among the zeta potentials of E. coli treated by gTPCs-5 h, gTPCs-12 h and gTPCs-24 h, but the bacterial contact angles of E. coli treated by gTPCs-5 h were higher compared with those of the other two gTPCs. Furthermore, gTPCs-5 h exhibited higher activity to decrease bacterial membrane proteins, and increase bacterial membrane permeability than the other two gTPCs. In conclusion, gTPCs with higher hydrophobicity property exhibited stronger antibacterial activity against E. coli.

Ribosomal Protein Database Profiling Lends Clarity to Ribosomal Protein Evolution and Mass Distribution

Existence of theoretical ribosomal protein mass fingerprint as well as utility of ribosomal protein as biomarkers in mass spectrometry microbial identification suggests phylogenetic significance for this class of proteins. To serve the above two functions, facile means of identifying and extracting important attributes of ribosomal proteins from proteome data file of microbial species must be found. Additionally, there is a need to calculate important properties of ribosomal proteins such as molecular weight and nucleotide sequence based on amino acid sequence information from FASTA proteome file. This work sought to support the above endeavour through developing MATLAB software that extracts the amino acid sequence information of all ribosomal proteins from the FASTA proteome data file of a microbial species downloaded from UniProt. Built-in functions in MATLAB are subsequently employed to calculate important properties of extracted ribosomal proteins such as number of amino acid residue, molecular weight and nucleotide sequence. All information above are output, as a database, to an Excel file for ease of storage and retrieval. Data available from the analysis of an Escherichia coli K-12 proteome revealed that the bacterium possesses a total of 59 ribosomal proteins distributed between the large and small ribosome subunits. The ribosomal protein ranges in sequence length from 38 (50S ribosomal protein L36) to 557 (30S ribosomal protein S1). In terms of molecular weight distribution, the profiled ribosomal proteins range in weight from 4364.305 Da (50S ribosomal protein L36) to 61157.66 Da (30S ribosomal protein S1). More important, analysis of the distribution of the molecular weight of different ribosomal proteins in E. coli reveals a smooth curve that suggests strong co-evolution of ribosomal protein sequence and mass given the tight constraints that a functional ribosome presents. Finally, cluster analysis reveals a preponderance of small ribosomal proteins compared to larger ones, which remains to be a mystery to evolutionary biologists. Overall, the information encapsulated in the ribosomal protein database should find use in gaining a better appreciation for the molecular weight distribution of ribosomal proteins in a species, as well as delivering information for using ribosomal protein biomarkers in identifying particular microbial species in mass spectrometry microbial identification.

Exopolysaccharide Features Influence Growth Success in Biocrust-forming Cyanobacteria, Moving From Liquid Culture to Sand Microcosms.

Land degradation in drylands is a drawback of the combined action of climate change and human activities. New techniques have been developed to induce artificial biocrusts formation as a tool for restoration of degraded drylands, and among them soils inoculation with cyanobacteria adapted to environmental stress. Improvement of soil properties by cyanobacteria inoculation is largely related to their ability to synthesize exopolysaccharides (EPS). However, cyanobacterial EPS features [amount, molecular weight (MW), composition] can change from one species to another or when grown in different conditions. We investigated the differences in growth and polysaccharidic matrix features among three common biocrust-forming cyanobacteria (Nostoc commune, Scytonema javanicum, and Phormidium ambiguum), when grown in liquid media and on sandy soil microcosms under optimal nutrient and water, in controlled laboratory conditions. We extracted and analyzed the released EPS (RPS) and sheath for the liquid cultures, and the more soluble or loosely-bound (LB) and the more condensed or tightly-bound (TB) soil EPS fractions for the sandy soil microcosms. In liquid culture, P. ambiguum showed the greatest growth and EPS release. In contrast, on the sandy soil, S. javanicum showed the highest growth and highest LB-EPS content. N. commune showed no relevant growth after its inoculation of the sandy soil. A difference was observed in terms of MW distribution, showing that the higher MW of the polymers produced by P. ambiguum and S. javanicum compared to the polymers produced by N. commune, could have had a positive effect on growth for the first two organisms when inoculated on the sandy soil. We also observed how both RPS and sheath fractions reflected in the composition of the soil TB-EPS fraction, indicating the role in soil stabilization of both the released and the cell attached EPS. Our results indicate that the features of the polysaccharidic matrix produced by different cyanobacteria can influence their growth success in soil. These results are of great relevance when selecting suitable candidates for large-scale cyanobacteria applications in soil restoration.

Effects of pretreatments on physicochemical and structural properties of proteins isolated from canola seeds after oil extraction by supercritical-CO2 process

The present research was to investigate the influences of pretreatments on the structural and physicochemical properties of proteins isolated from canola seeds (CSP) after oil extraction by supercritical CO2 fluid. The results showed that the CSPs pretreated with microwave treatment (MV-CSP) and ultrasound treatment (UL-CSP) significantly differed in terms of molecular weight distribution, amino acid composition, and the primary conformation of CSP. The crystalline properties and secondary structural conformation as well as average particle sizes of CSPs were not significantly influenced by pretreatments, but the morphological characteristics were remarkably changed. The physicochemical properties including solubility, water/oil holding capacity, emulsifying capacity and stability, as well as foaming capacity and stability were substantially altered by the pretreatments. The MV-CSP and UL-CSP possessed better physicochemical characteristics. Therefore, microwave- and ultrasound-pretreatments could serve as potential technologies to improve the physicochemical properties of canola seeds proteins. Moreover, different oil extraction methods greatly influenced the quality and functional properties of isolated CSPs. The supercritical CO2 (SC–CO2) process protected intact functional properties and enhanced the overall quality of the isolated CSPs compared to solvent extraction.

Stability of TEMPO-oxidized cotton fibers during natural aging

Stability of cotton fibers oxidized by the 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated system during natural aging was monitored; the oxidized and five-year-aged fibers were characterized in terms of molecular weight distribution, quantity and distribution of functionalities, tensile strength, color difference, and yellowness index. The distribution of functionalities introduced in cotton fibers by TEMPO-mediated oxidation and subsequent aging was investigated by means of gel permeation chromatography using multiple detection and group-selective labeling. The mild TEMPO-mediated oxidation retains the molar mass of oxidized cotton, but this status is not stable during natural aging. For highly oxidized cotton, the molar mass of aged fibers is low but stable. Aged TEMPO-oxidized cotton shows a prominent discoloration and an increased yellowness index. For tensile strength, the limiting value was obtained for aged TEMPO-oxidized cotton, regardless of whether the samples had initially been oxidized with a low or high degree of oxidation.

Fully Recyclable Bio-Based Thermoplastic Materials from Liquefied Wood.

A novel, low-cost, and fully recyclable thermoplastic material is produced from liquefied lignocellulosic biomass and natural fibers. The matrix, which is the heavy fraction of the liquefaction product, is characterized in terms of molecular weight distribution, density, viscosity, softening point and tensile strength. It is possible to increase the mechanical strength of the matrix by a factor of up to 100 by reinforcing it with flax fibers. Specifically, the tensile strength increased from 0.4 MPa for the non-reinforced matrix, to 55 MPa for the matrix/flax composite with a fiber content of 20 wt %. These values are comparable to conventional thermoplastics, such as poly(methyl methacrylate), polyvinyl chloride, or polystyrene.

Comparative Study of Chemical Composition, Molecular and Rheological Properties of Silicone Oil Medical Devices.

PurposeWe evaluated chemical composition, and molecular and rheological properties in 10 commercially available silicone oils (SilOils), focusing on siloxane chains of low molecular weight (LMW components, LMWC) that are known to be “impurities” produced during the SilOil synthesis process.MethodsWe assessed the type of SilOil polymer and molecular weight distribution (MWD) by spectroscopy and conventional size exclusion chromatography, respectively. From the Cumulative MWD, we calculated the fractions of LMWC with molecular weight (M): ≤2000, ≤5000, and ≤10,000 g/mol. Due to the low MW, the content of LMWC with M ≤1000 g/mol was determined by gas chromatography-mass spectrometry. The dynamic viscosity (η) was assessed by rotational rheometry.ResultsFor all SilOils, the polymer was polydimethylsiloxane. The samples differed significantly in terms of MWD and relative LMWC fractions. Specifically, the relative fraction of all LMWC (M ≤10,000 g/mol) ranged from 2.31% to 9.40% and the content of LMWC with M ≤1000 g/mol also varied significantly (range, 51–1151 ppm). The η values were different between the SilOils, and, for many of them, from the declared viscosity.ConclusionsCommercially available SilOils differ significantly in molecular and rheologic features. These compounds contain a significant amount of LMWC, “impurities” generated during the synthesis process, acting as emulsifier, potentially inducing ocular inflammation and toxicity.Translational RelevanceThe amount of impurities in different SilOils may influence significantly their biocompatibility.

Influence of wax inhibitor molecular weight: Fractionation and effect on crystallization of polydisperse waxes

The influence of wax inhibitor molecular weight on wax crystallization was investigated in three steps: (1) Wax inhibitor fractionation via stepwise precipitation or ultrasonic disintegration, (2) characterization of inhibitor and sub-fractions in terms of molecular weight distribution, hydrodynamic radius, and precipitation from pure solvent, and (3) inhibitor effect on wax appearance temperature (WAT), waxy gelling, and wax crystal morphology. Stepwise precipitation yielded narrower molecular weight distributions, whereas ultrasonic disintegration reduced the average molecular weight and increase the polydispersity index. Changes in inhibitor molecular weight could improve as well as diminish WAT depression. Waxy gelation temperature showed similar trends, but overall effects were more pronounced. It was concluded the wax inhibitor molecular weight is a parameter that can be used to fine-tune additives to a particular waxy oil, but only after an effective PPD type has been identified.

Catalyst: Size Distribution in Self-Assembly Matters

Dafni Moatsou completed her PhD in chemistry at the University of Warwick in 2015, was a Marie Sklodowska-Curie fellow at the Adolphe Merkle Institute until 2017, and is a junior research group leader at the Karlsruhe Institute of Technology, where she focuses on sequence control and self-assembly of polymers. Rachel O’Reilly completed her PhD in 2003 at Imperial College London. She currently holds a chair in chemistry within the College of Engineering and Physical Sciences at the University of Birmingham. In August 2018 she became the head of the School of Chemistry. Her research targets the design, synthesis, and application of polymeric materials, where control over architecture, functionality, and reactivity are central to their application.

Effect of γ-Irradiation of Cellulose on the Molecular-Weight Characteristics of Nitro Esters Produced from It

The effect of γ-irradiation of cotton cellulose on the molecular-weight distribution (MWD) of the nitro esters prepared from the irradiated cellulose has been studied. It has been established that the degradation of cellulose during the sulfuric acid–free nitration in fuming nitric acid occurs according to a random law with the most probable MWD, whereas the esters obtained in a sulfuric acid–nitric acid nitration mixture are almost uniform in terms of MWD. The rate constants of degradation by nitration increase with the absorbed dose. An increase in the uniformity of the nitro esters as a result of the washing out of the low-molecular-weight fraction improves their physicomechanical characteristics. An equation is proposed for describing the kinetics of degradation of irradiated cotton cellulose during its nitration in fuming nitric acid.

Sugarcane straw lignin obtained by sulfur dioxide-alcohol-water (SAW) fractionation: Effect of solvent

Sugarcane straw (SCS) lignin is extracted by SO2-Alcohol-Water (SAW) fractionation (155 °C, 1 h) using methanol, ethanol or isopropanol as pulping solvent (SO2/Alcohol/Water = 12/44/44 wt%). The SAW fractionation removes 90–95% lignin from SCS of which only 30–45% is isolated as precipitated lignin after solvent evaporation. The precipitated and pulp residual lignin (5–10%) are analyzed for their degree of sulfonation (S/C9) while precipitated lignin is further analyzed in terms of molecular weight distribution (MWD) and alkoxylation reactions. Similar S/C9 values for methanol, ethanol and isopropanol lignin show that the degree of sulfonation is independent of fractionation solvent. However, the sulfonated lignin is comparatively less soluble in the methanol-based liquor compared to the corresponding lignins in the ethanol- and isopropanol-based liquors. The mass average molecular weight, Mw, is highest for isopropanol lignin (∼3800) while the numbers for methanol and ethanol lignins are comparatively smaller but nearly equal in magnitude (∼3000). Alkoxyl groups and nuclear magnetic resonance (NMR) analyses are performed to interpret the differences in lignin Mw and alkoxylation reactions. Different ether and ester type linkages are identified in NMR spectra confirming lignin alkoxylation. Lignin carbohydrate complexes (LCC) are also found in NMR spectra confirming that some of the detected carbohydrates are covalently bound to lignin.

Synthesis and Characterization of NBR´s by RAFT Technique and their use as Rubber Precursor in ABS Type Resins

Different rubbers based on polybutadiene were synthesized in solution by the reversible addition-fragmentation chain-transfer polymerization (RAFT) technique using 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl] entanoic acid as RAFT agent and 1,1’-azobiscyclohexanecarbonitrile (Vazo-88) as initiator. The results obtained in the polymerization of polybutadiene and poly(butadiene-co-acrylonitrile) (NBR) are discussed in terms of molecular weight distribution, composition and microstructure. Composition of polybutadiene in NBR´s was kept constant along the copolymerization, and the vinyl, cis and trans isomers are shown in values of around 12, 26 and 62% in all cases. Resulting rubbers were used to synthesize acrylonitrilebutadiene-styrene (ABS) type resins through an in situ bulk polymerization. Dynamic-mechanical properties and the morphology were analyzed in all the different ABS resins. In DMA analyses, the rubber component presented two transitions as well as an increase in the magnitude of the transition located around -75 °C, which is explained by the significant amount of SAN occlusions in the morphology, analyzed by TEM.

Poly(N‐vinylpyrrolidone)–polydimethylsiloxane amphiphilic ABA triblock copolymers

ABSTRACTTriblock copolymers of N‐vinylpyrrolidone (NVP) and polydimethylsiloxane (PDMS) were synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization using two different types of difunctional telechelic PDMS‐based dixanthate macroinitiators. The incorporation of PDMS into the triblock copolymers was evidenced by 1H NMR spectroscopy and varied between 4 mol % and as high as 20 mol %, dependent on reaction time and monomer conversion. The copolymer homogeneity was characterized in terms of molecular weight distribution determined by GPC to estimate the level of control over the chain length. Monomodal molecular weight distributions were observed, and 1H NMR spectroscopy indicated the copolymers had number average molecular weights (Mn) ranging between 28,000 and 160,000 g/mol. In addition, thin film phase separation and critical micelle concentrations for these copolymers were analyzed via transmission electron microscopy and surface tension measurements, respectively. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3387–3394

Simulation of NOM events in pilot plant evaluation of DAF/Ozone/BAC for drinking water treatment

Abstract Pilot plant testing is invaluable for ascertaining the robustness of water treatment processes against raw water quality events such as turbidity and colour spikes, whether it be for stress testing of an existing process or designing of a new process. Unfortunately, the natural occurrence of such events (particularly colour) can be difficult to predict and commercial humic materials generally fail to closely match the indigenous natural organic matter (NOM) present in the raw water. Therefore, it is highly desirable to be able to simulate NOM event conditions. This paper describes a simple brewing method that we developed and used in our recent pilot plant evaluation of a proposed DAF/Ozone/BAC process for drinking water treatment. Using this method we successfully prepared, by using fallen leaves etc. collected from the local catchment area, large quantities of a concentrated NOM stock solution with its specific ultraviolet absorbance (SUVA), when diluted, very close to the median SUVA of historical NOM events. The brewed solution showed broadly similar NOM characteristics to those of the raw water encountered during the pilot investigation period in terms of molecular weight distribution and fractionation. The coagulation behaviour was also examined for the spiked and non-spiked raw water.

Amino acid composition and antioxidative properties of hydrolysed pumpkin (Cucurbita pepo L.) oil cake protein

ABSTRACTPumpkin oil cake protein isolate (POCPI) was hydrolysed using two food-grade enzymes alcalase and trypsin. Alcalase-hydrolysed POCPI (POCPH1) was selected as the optimum treatment based on the DPPH radical scavenging, total antioxidative, and ferrous ion chelating activities. Amino acid composition showed a direct relationship between the antioxidative activity of POCPH1 and the amount of hydrophobic amino acids that formed 33.49% of its total amino acids. Surface hydrophobicity decreased as a result of hydrolysis and potent thermal and pH stability was observed in POCPH1 (p ˂ 0.05). In terms of molecular weight distribution, size exclusion chromatogram indicated that the majority of peptides possessed molecular weight less than 6.5 kDa. Based on the results, POCPH1 could be employed as a natural antioxidative agent with strong pH and thermal stability.

Molecular weight distribution of pollutants in leachate from full scale landfill site

<div> <p>The main objective of this study was to investigate the differences between the main pollutants in young and intermediate age landfill leachate in terms of molecular weight distribution (MWD). Parameters of chemical oxygen demand (COD), five day - biochemical oxygen demand (BOD<sub>5</sub>), ultraviolet-visible spectrophotometry (UV-VIS spectrum), total kjehldahl nitrogen (TKN), ammonia nitrogen (NH<sub>4</sub>-N) and colour were fractioned by membranes with the nominal pore size of 1µm, 0.05 µm, 100 kDa, 50 kDa, 10 kDa, 1 kDa and 0.5 kDa. According to the MWD results appropriate treatment technology could be choosen easily. According to the MWD results the ratio of soluble fractions (< 0.5 kDa) to total COD was 34% in young leachate (YL), whereas low molecular weight (MW) fractions were dominant in intermediate leachate (IL) having this ratio of 71%. Presence of lower MW compounds in IL was also confirmed with UV-VIS absorbance spectra and its spectrum was higher than the YL. According to the specific ultraviolet absorption (SUVA) values, the organic contents of all of these processes were hydrophilic. TKN and NH<sub>4</sub>-N analysis showed that in IL all the nitrogen present is in ammoniacal form, instead in YL there is still the presence of organic nitrogen. Furthermore more than half of the TKN was less than 0.5 kDa while 6 % and 16 % TKN found in wastewater from IL and YL was higher than 1 µm respectively. The observations of this study may provide useful criteria to choose a suitable landfill leachate treatment processes.</p> </div> <p> </p>

Analysis of silicones released from household items and baby articles by direct analysis in real time-mass spectrometry.

Direct analysis in real time-mass spectrometry (DART-MS) enables screening of articles of daily use made of polydimethylsiloxanes (PDMS), commonly known as silicone rubber, to assess their tendency to release low molecular weight silicone oligomers. DART-MS analyses were performed on a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Flexible silicone baking molds, a watch band, and a dough scraper, as baby articles different brands of pacifiers, nipples, and a teething ring have been examined. While somewhat arbitrarily chosen, the set can be regarded as representative of household items, baby articles, and other objects made of silicone rubber. For comparison, two brands of silicone septa and as blanks a glass slide and a latex pacifier were included. Differences between the objects were mainly observed in terms of molecular weight distribution and occasional release of other compounds in addition to PDMS. Other than that, all objects made of silicone rubber released significant amounts of PDMS during DART analysis. To provide a coarse quantification, a calibration based on silicone oil was established, which delivered PDMS losses from 20 μg to >100 μg during the 16-s period per measurement. Also, the extraction of baking molds in rapeseed oil demonstrated a PDMS release at the level of 1 μg mg(-1). These findings indicate a potential health hazard from frequent or long-term use of such items. This work does not intend to blame certain brands of such articles. Nonetheless, a higher level of awareness of this source of daily silicone intake is suggested.

Structure Development of Low-Density Polyethylenes During Film Blowing: A Real-Time Wide-Angle X-ray Diffraction Study

We studied experimentally the structure development during film blowing for three different low-density polyethylenes at four different processing conditions. For this, we combined blown film extrusion with in situ X-ray diffraction at a synchrotron radiation beam line. The measurements were performed at rheological similar conditions at the die exit, with each grade possessing different molecular properties in terms of molecular weight distribution and branching content. The development of crystallinity and molecular orientation was determined as function of the distance from the die. It is shown that this approach provides a valuable method to study structure evolution during film blowing and can be used to validate results from numerical models and help to improve and/or extend these models.

Foulant analysis of a reverse osmosis membrane used pretreated seawater

This study focused on the characterization of organic and biological foulants on reverse osmosis (RO) membrane and fouled RO membrane characterization with seawater pretreated by submerged membrane hybrid systems (SMHSs). New low pressure membrane based pretreatments namely submerged membrane coagulation hybrid system (SMCHS) and submerged membrane coagulation-adsorption hybrid system (SMCAHS) were investigated. Organic foulants on RO membrane were characterized in terms of molecular weight distribution (MWD), fluorescence and extracellular polymeric substance (EPS) analyses. The organic foulants were mainly composed of high molecular weight matters representing biopolymers in the foulants. The fluorescence excitation–emission matrix (F-EEM) analysis showed that protein-like materials were dominant with samples pretreated by SMHSs. Humic-like materials which have lower aromaticity were also present in the foulant. Biological foulants were investigated in terms of total direct cell (TDC) count, cell viability and biomass activity (adenosine tri-phosphate; ATP). Biological fouling was found to be reduced by organic removal with SMHSs. The fouled membranes were characterized using environmental scanning electron microscopy coupled with energy dispersive spectroscopy, attenuated total reflection-Fourier transform infrared spectrometry, zeta-potential measurement, atomic force microscopy, and contact angle measurement.

Sequential solvent fractionation of heterogeneous bamboo organosolv lignin for value-added application

Value-added utilization of lignin is affected by its heterogeneous nature. In this case, bamboo organosolv lignin was successively fractionated with organic solvents of increasing dissolving capacity (i.e., ether, ethyl acetate, methanol, acetone, and dioxane/water) to obtain homogeneous preparations. The starting lignin and the fractions obtained were compared in terms of molecular weight distribution and functional groups by a set of chemistry and spectroscopy technologies. It was found that the yield of the five fractions obtained was 2.80%, 39.85%, 18.64%, 23.38%, and 13.30%, respectively. The lignin fraction extracted with ethyl acetate contained homogeneous materials of low molecular weight whereas the lignin fraction extracted with acetone was composed of a mixture of medium and high molecular weight materials. As evidenced by sugar analysis, there was strong association between hemicelluloses and lignin in the preparations with different molecular weights. Spectroscopy analysis indicates that with increasing the dissolving capacity of solvent, the contents of methoxyl, phenolic, and aliphatic hydroxyl groups in the extracted lignin fractions were decreased. The lignin fraction extracted with ethyl acetate, having a high radical scavenging index (RSI), will be a good feedstock as stabilizer. The results above suggest that the sequential solvent fractionation provides a promising way to prepare lignin with homogeneous structure and good functional properties for potential application.