Large Molecular Weight Polymers Research Articles

The auronidin flavonoid pigments of the liverwort Marchantia polymorpha form polymers that modify cell wall properties.

Plant adaptation from aquatic to terrestrial environments required modifications to cell wall structure and function to provide tolerance to new abiotic and biotic stressors. Here, we investigate the nature and function of red auronidin pigment accumulation in the cell wall of the liverwort Marchantia polymorpha. Transgenic plants with auronidin production either constitutive or absent were analysed for their cell wall properties, including fractionation of polysaccharide and phenolic components. While small amounts of auronidin and other flavonoids were loosely associated with the cell wall, the majority of the pigments were tightly associated, similar to what is observed in angiosperms for polyphenolics such as lignin. No evidence of covalent binding to a polysaccharide component was found: we propose auronidin is present in the wall as a physically entrapped large molecular weight polymer. The results suggested auronidin is a dual function molecule that can both screen excess light and increase wall strength, hydrophobicity and resistance to enzymatic degradation by pathogens. Thus, liverworts have expanded the core phenylpropanoid toolkit that was present in the ancestor of all land plants, to deliver a lineage-specific solution to some of the environmental stresses faced from a terrestrial lifestyle.

An experimental investigation on drag reduction by a combination of polymer, Laurel soap and palm fiber through circulated Newtonian liquid

Flowability and reduced pressure are some of the economic values in pipeline transportation. In this study, we investigated the functionality of self-made drag coefficients composed of a combination of large molecular weight polymer, Laurel soap, and date palm fiber which were induced into a circulated piping system under turbulent water flow. The proposed combination formulas are proved to be a new cost-effective drag reduction approach. The efficiency of using a mixture of polymer, palm fiber, and soap on the drag reduction was thoroughly evaluated via investigating several case studies. Using pure polyelectrolyte showed that at the highest polymer concentration (50 ppm), the percentage of drag reduction reaches 50% in 10.3 mm pipe diameter and 70% drag reduction in 13.5 mm pipe diameter at a flow of low Reynolds number counted 17166.7. Upon applying a mixture of polyelectrolyte composed of (50 ppm) and fiber in the range (30-60 ppm), a drag reduction of 63% in 10.3 mm pipe diameter and 76% in 13.5 mm pipe diameter were achieved, respectively. Upon examining a mixture composed of polyelectrolyte (50 ppm) and soap in a range (50-150 ppm), the results showed that the highest drag reduction was achieved at a low concentration of soap and a bulk flow at a low Reynolds number. The aforementioned performance results were exemplified attaining drag reductions of 70% in 10.3 mm pipe diameter and 96% in 13.5 mm pipe diameter, respectively. This is accomplished through optimizing the applied mixture formulas. The estimated drag reductions were shown higher when applying the polymer mixture compared to that of pure polymer. However, a slight decrease in the attained drag reductions when using polymer-soap was observed and attributed to the hindrance from the palm fiber, which ultimately reduces the chance for all soap particles to reach the stagnant wall layer

Improvement in the functional properties of quinoa (Chenopodium quinoa) protein isolates after the application of controlled heat-treatment: Effect on structural properties

Quinoa protein isolates (QPIs) were subjected to controlled heat-treatment (80−100 °C) at variable time (15−30 min). Results showed that heat-treatment induced structural changes in QPIs. Circular dichroism showed loss of secondary structure of QPIs, particularly α-helix and β-sheet. Total and exposed SH groups were significantly (p ≤ 0.05) lower in heat-treated QPIs. SDS-PAGE profile showed formation of soluble protein aggregates with smaller particle size. Particle size decreased when QPIs were heated at 80 °C for 30 min. Solubility and turbidity of heat-treated QPIs improved significantly. Decline in crystallinity was due to denaturation of protein molecules by heat-treatment. Water binding capacity, oil binding capacity, emulsifying activities and stabilities were found lower in QPIs heat-treated at higher thermal temperatures for longer time. This might be due to decline in total and exposed SH contents, accelerated conversion of SH groups into disulfide bonds and formation of large molecular weight polymers or protein aggregates due to polymerization reactions. Higher foaming capacity (89.99 %) and foaming stability values of 167.80 % (10 min) and 124.15 % (20 min) were found in QPIs heated at 80 °C for 30 min. The results thus suggests that heat-treatment carried out at lower heating temperatures had improved the functional properties of QPIs.

Effects of microwave heating, steaming, boiling and baking on the structure and functional properties of quinoa (Chenopodium quinoa Willd.) protein isolates

SummaryThe effects of microwave heating (MW), steaming (SM), boiling (BL) and baking (BK) on the structure and functional properties of quinoa protein isolates (QPI) were investigated. SDS‐PAGE showed the 20–30 kDa band strength of QPI‐BL was enhanced, which indicated the disulphide bond was broken and protein molecules dissociated. Due to the recombination of subunits, some large molecular weight or insoluble polymer components of QPI‐SM and QPI‐BK did not pass through the gel. Microwave heating and boiling showed negative effects for α‐helix and positive effects for β‐sheet, which implied the molecular structure was transformed from ordered to disordered, the secondary structure became loose. The reduction of free SH (sulfhydryl) and surface hydrophobicity implied that aggregation and cross‐linking of protein molecules for QPI‐SM and QPI‐BK. QPI, QPI‐MW and QPI‐BL exhibited better solubility, which was related to the water holding capacity (WHC) and emulsification. For QPI‐SM and QPI‐BK, functional properties (including solubility, WHC and gel‐forming ability) decreased due to molecular aggregation. Heat treatments significantly affect the structure and functional properties of QPI, the current research showed that microwave heating and boiling might be better heat treatment methods for QPI and would help the development of quinoa protein products.

Kinetics of growth of non-equilibrium fluctuations during thermodiffusion in a polymer solution.

A thermal diffusion process occurring in a binary liquid mixture is accompanied by long ranged non-equilibrium concentration fluctuations. The amplitude of these fluctuations at large length scales can be orders of magnitude larger than that of equilibrium ones. So far non-equilibrium fluctuations have been mainly investigated under stationary or quasi-stationary conditions, a situation that allows to achieve a detailed statistical characterization of their static and dynamic properties. In this work we investigate the kinetics of growth of non-equilibrium concentration fluctuations during a transient thermodiffusion process, starting from a configuration where the concentration of the sample is uniform. The use of a large molecular weight polymer solution allows to attain a slow dynamics of growth of the macroscopic concentration profile. We focus on the development of fluctuations at small wave vectors, where their amplitude is strongly limited by the presence of gravity. We show that the growth rate of non-equilibrium fluctuations follows a power law [Formula: see text] as a function of time, without any typical time scale and independently of the wave vector. We formulate a phenomenological model that allows to relate the rate of growth of non-equilibrium fluctuations to the growth of the macroscopic concentration profile in the absence of arbitrary parameters.

HMDSO-plasma coated electrospun fibers of poly(cyclodextrin)s for antifungal dressings

Electrospun mats containing cyclodextrin polymers (poly-αCD or poly-βCD) were developed to act as wound dressings showing tunable release rate of the antifungal agent fluconazole incorporated forming inclusion complexes. Poly-αCD and poly-βCD were prepared via cross-linking with epichlorohydrin (EPI) as water-soluble large molecular weight polymers. Then, polyCDs forming complexes with fluconazole were mixed with poly-(ε-caprolactone) (PCL) or poly(N-vinylpyrrolidone) (PVP) for electrospinning. Obtained bead-free fibers showed a random distribution, diameters in the 350–850nm range, and a variety of physical stability behaviors in aqueous environment. Mats were coated by hexamethyldisiloxane (HMDSO) plasma polymerization to create a hydrophobic layer that prevented rapid drug diffusion. HMDSO coating was evidenced by the Si content of mat surface (EDX analysis) and by the increase in the water contact angle (up to 130°). In physiological-mimicking medium, non-treated mats showed burst release of fluconazole, whereas HMDSO-coated mats sustained the release and delayed disintegration of PVP-based mats. Antifungal tests evidenced that both coated and non-coated mats efficiently inhibited the growth of Candida albicans.

Large Molecular Weight Polymer Solar Cells with Strong Chain Alignment Created by Nanoimprint Lithography.

In this work, strong chain alignment in large molecular weight polymer solar cells is for the first time demonstrated by nanoimprint lithography (NIL). The polymer crystallizations in nonimprinted thin films and imprinted nanogratings with different molecular weight poly(3-hexylthiophene-2,5-diyl) (P3HT) are compared. We first observe that the chain alignment is favored by medium molecular weight (Mn = 25 kDa) P3HT for nonimprinted thin films. However, NIL allows large molecular weight P3HT (>40 kDa) to organize more strongly, which has been desired for efficient charge transport but is difficult to achieve through any other technique. Consequently P3HT/[6,6]-penyl-C61-butyric-acid-methyl-ester (PCBM) solar cells with large molecular weight P3HT nanogratings show a high power conversion efficiency of 4.4%, which is among the best reported P3HT/PCBM photovoltaics devices.

Periodically sequenced peptides: A new tool for nanoscale materials synthesis

Event Abstract Back to Event Periodically sequenced peptides: A new tool for nanoscale materials synthesis Matthew Kubilius1 and Raymond S. Tu1 1 City College of New York, Chemical Engineering, United States Synthesizing useful, periodically-sequenced, self-assembling, amphipathic polypeptides is difficult due to increasing polydispersity indices of large molecular weight polymer systems. Accounting for this, we engineered amino acid dimers that polymerize into amphipathic chains with alternating hydrophilic/hydrophobic side groups. This system's periodicity is typical of amino acid sequences that self-assemble into beta-sheets. We limit polydispersity in the growing polypeptide chains through changes to the kinetics of growth by transport-limited chain elongation and partitioning of large molecular weight polypeptides to interfaces. We show that in the absence of a bulk micellular interface, standard condensation polymerization occurs. However, the amphipathic character of our peptide chains increases with increasing molecular weight, resulting in a polypeptide that preferentially partitions into surfactant micelles with increasing molecular weight. Grown that way, with exposure to large, diffuse, bulk-phase interfacial areas, this kinetically-limited growth narrows the polydispersity of our polypeptides. We quantify polydispersity indices using multi-angle light scattering and characterize evolving sheet-like secondary structure using circular dichroism for various amino acid dimer systems. Our results show that the peptides grown in micelle-containing media show significantly enhanced self-assembly and narrowed polydispersity indices. We further characterize these self-assemblies as Langmuir-Blodgett films when the polypeptide partitions strongly to an air-water interface, and image them using Brewster angle microscopy. We conclude that transport-limited polymerization shows great promise in the synthesis of low-cost, surface-active, self-assembling polypeptides. National Science Foundation, Division of Materials Research; National Science Foundation, Chemical, Bioengineering, Environmental, and Transport Systems Keywords: self-assembly, amphiphile, Polymeric material, Polypeptide Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Naturally-derived materials and biopolymers Citation: Kubilius M and Tu RS (2016). Periodically sequenced peptides: A new tool for nanoscale materials synthesis. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.02762 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Matthew Kubilius Raymond S Tu Google Matthew Kubilius Raymond S Tu Google Scholar Matthew Kubilius Raymond S Tu PubMed Matthew Kubilius Raymond S Tu Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Contact line motion of polymer solution inside capillary

In this research we investigated the contact line motion of polyacrylamide solutions in glycerin inside glass capillaries. Three different molecular weights of 100,000 (100k), 610,000 (610k) and 5,000,000g/mole (5M) were used. It was hypothesized that the depletion of large polymers from the contact line region by migration strongly affects the contact line speed and experiments were carried out to confirm whether this hypothesis is applied to the present system. The experimental results for large molecular weight polymers (5M) are consistent with the migration theory while those for small molecular weight polymers (100k) do not show the migration effect. The 610k polymers show either 5M or 100k behavior depending on concentration and contact line speed. These experimental observations are consistent with the migration theory. The positive first normal stress difference (N1) of 100k polymer solutions also affects the contact line speed. N1 of 5M polyacrylamide solutions does not appear to strongly affect the contact line motion, which also supports the polymer depletion near the contact line due to the migration. The result of the present experimental research independently supports the previous reports on the contact line motions of polymer solutions using the drop spreading method and the theoretical analysis (Han and Kim, 2013, 2014).

The cryoprotective effect of Ficoll on the rabbit spermatozoa quality.

The aim of this study was to evaluate the effect of the addition of Ficoll 70 into the cryopreservation medium containing sucrose and dimethyl sulfoxide (DMSO) on rabbit spermatozoa characteristics following freezing/thawing. This large molecular weight polymer elevates the viscosity of medium and, therefore, could better protect spermatozoa during the freezing process. Only ejaculates of good initial motility (>80%) were used in the experiments. Heterospermic pools were diluted in a freezing medium composed of commercial diluent, 16% dimethyl sulphoxide (DMSO) and 2% sucrose (control) or in the same medium enriched with 4% Ficoll 70 (Ficoll) and frozen in liquid nitrogen vapours for 10 min before being plunged in liquid nitrogen. The quality of fresh and frozen/thawed spermatozoa samples was evaluated in vitro using the Computer Assisted Semen Analysis (CASA) system, fluorescent probes (peanut agglutinin (PNA)-Alexa Fluor®; annexin V-FLOUS) and by electron microscopy. Better cryoprotective effect was observed when Ficoll 70 was added, compared with the semen cryopreserved with sucrose and DMSO only. The higher values (P < 0.05) of motile and progressively moving spermatozoa immediately after thawing and at 30 min following incubation at 37°C were obtained in the Ficoll group. Moreover, the higher number (P < 0.05) of acrosome intact sperm was found in the Ficoll compared with the control group. Furthermore, no significant differences in kindling rates and number of pups born between frozen/thawed and fresh semen group were found. In conclusion, our study showed that the addition of Ficoll 70 might improve several characteristics of rabbit spermatozoa measured in vitro following freezing/thawing.

Transforming large molecular weight pectin and chitosan into oral protein drug nanoparticulate carrier

Polymeric nanoparticle formation is characterized by high risks of premature drug leaching and low drug encapsulation efficiency. This is aggravated by slow nanoparticle formation by large molecular weight polymers due to their slow diffusion kinetics in the reaction medium. This study investigated model protein drug insulin encapsulation by large molecular weight pectin and chitosan. The nanoparticles were prepared through pectin–chitosan coacervation and when necessary, together with pectin or chitosan crosslinking by calcium or tripolyphosphate ions in the same process. The formed particles were nanospray-dried when required. The size, zeta potential, morphology, drug content, drug association efficiency, polymer–polymer and drug-polymer interaction in particulate matrix were examined. The pectin–chitosan nanoparticles were able to encapsulate insulin substantially only if these nanoparticles were formed with rapid particle aggregation into micromatrices as a result of particle surfaces attracting the oppositely charged polymer chains via crosslinking as well as coacervation processes. The particulate aggregation level of micromatrices can be reduced via nanospray drying. Small discrete nanoparticles were obtainable from micromatrices.

Rheology of polymer solutions using colloidal-probe atomic force microscopy

We use colloidal-probe atomic force microscope (AFM) to study the rheological behavior of polymer solutions confined between two surfaces: the surface of a sphere and a flat surface on which the fluid is deposited. Measurements of the hydrodynamic force exerted on the sphere by the flowing liquid allowed retrieving the viscosity of the solution for different distances between the sphere and the flat surface. This method has been experimentally tested for Newtonian fluids for which the viscosity does not vary versus the gap dimensions. On the other hand, for non-Newtonian fluids, such as the large molecular weight polymer solutions used here, the measured viscosity depends on the gap height D between the flat surface and the sphere. The decrease of the viscosity versus gap height is similar to previously observed variations in colloidal suspensions. Depletion of polymers in the gap region due to the high shear rates involved is a possible cause for such a variation.

Magnetic mesoporous silica hybrid nanoparticles for highly selective boron adsorption

Novel core–shell magnetic mesoporous silica hybrid nanoparticles were synthesized and functionalized further with a glycidol reagent to produce boron-specific cis-diol, chelating functional derivatives. The resulting core–shell hybrid nanoparticles were found to be a better alternative to the existing boron adsorbents that had been modified with large molecular weight saccharide moieties and polymer functionalities. The magnetic mesoporous silica hybrid nanoparticles had a surface area, diameter, pore size, and saturation magnetization of 629 m2 g−1, 200–300 nm, 2.5 nm, and 33.25 emu g−1, respectively. The glycidol-modified nanoparticles with cis-diol functional groups showed high adsorption affinity and excellent selectivity towards boron in an aqueous solution, even in the presence of competitive metal ions (Ni2+, Cu2+, Cr2+ and Fe2+) and sulphates and chlorides of Na+, K+, Ca2+ and Mg2+ ions. Adsorption equilibrium could be established within 15–20 min, and the level of boron adsorption was 2.37 mmol g−1, which is much higher than the values previously reported for other boron adsorbent materials. The synthesized magnetic mesoporous silica hybrid nanoparticles showed approximately 97% boron removal capacity from a H3BO3 solution (100 mg L−1), and the used adsorbent particles could be separated easily from the aqueous suspensions by an external magnetic field. The adsorbent could be used repeatedly after a simple acid treatment (0.1 M HCl) and regenerated by an aqueous ammonia solution (3% NH3·H2O).

Interior engineering of a viral nanoparticle and its tumor homing properties.

The development of multifunctional nanoparticles for medical applications is of growing technological interest. A single formulation containing imaging and/or drug moieties that is also capable of preferential uptake in specific cells would greatly enhance diagnostics and treatments. There is growing interest in plant-derived viral nanoparticles (VNPs) and establishing new platform technologies based on these nanoparticles inspired by nature. Cowpea mosaic virus (CPMV) serves as the standard model for VNPs. Although exterior surface modification is well-known and has been comprehensively studied, little is known of interior modification. Additional functionality conferred by the capability for interior engineering would be of great benefit toward the ultimate goal of targeted drug delivery. Here, we examined the capacity of empty CPMV (eCPMV) particles devoid of RNA to encapsulate a wide variety of molecules. We systematically investigated the conjugation of fluorophores, biotin affinity tags, large molecular weight polymers such as poly(ethylene glycol) (PEG), and various peptides through targeting reactive cysteines displayed selectively on the interior surface. Several methods are described that mutually confirm specific functionalization of the interior. Finally, CPMV and eCPMV were labeled with near-infrared fluorophores and studied side-by-side in vitro and in vivo. Passive tumor targeting via the enhanced permeability and retention effect and optical imaging were confirmed using a preclinical mouse model of colon cancer. The results of our studies lay the foundation for the development of the eCPMV platform in a range of biomedical applications.

Multilayered silicone oil droplets of narrow size distribution: Preparation and improved deposition on hair

Silicone oil droplets have limited deposition on hair due to electrostatic repulsion with negative surface charge of hair substrates. Aiming to improve silicone deposition on hair substrates, surface properties of uniform-sized silicone oil droplets (produced by membrane emulsification) were modified using layer-by-layer electrostatic deposition. By using this method, silicone oil droplets were coated with large molecular weight polymers, i.e. quaternized chitosan and alginate, and low molecular weight compounds, i.e. diallyl dimethyl ammonium chloride and glycerol to obtain six alternate layers of different surface charges. It was found that the dispersion of coated silicone oil droplets of narrow size distribution exhibited much improved mechanical strength and increased viscosity against shear compared to uncoated droplets. These multilayered silicone oil droplets were then added into model shampoos and conditioners to study the effect of charge and molecular weight of coating materials on silicone oil deposition on hair. The results clearly demonstrated that surface charge and charge density have significant influence on silicone oil deposition. Droplets with higher positive charge density resulted in increased deposition of silicone on hair due to electrostatic attraction. Characterization of the hair surface potential, wetting properties and friction certified the results further, showing reduced friction, decreased wetting angle and positive surface potential of high density positively charged silicone oil droplets. Therefore, LBL surface modification combined with membrane emulsification is a promising method for preparing multilayered silicone oil droplets of increased mechanical strength, viscosity and deposition on hair.

Steady shear microstructure in dilute colloid–polymer mixtures

The shear-induced microstructure in dilute colloid–polymer mixtures, where the presence of polymer induces a tuneable attractive interaction between the colloids, is investigated using quantitative confocal microscopy, over a wide parameter space including the shear rate, the polymer concentration, and two different polymer molecular weights corresponding to polymer/colloid size ratios of approximately 0.02 and 0.05. Overall, the imposition of low shear rates radically transforms the relatively uniform quiescent structure into one marked by long-range heterogeneities and pronounced segregation of dense clusters and voids. Increasing the rate of deformation effects a consistent decrease in the average cluster size and a gradual transition towards a more homogeneous structure through the redistribution of voids. Interestingly, at high shear rates, the suspension microstructure for the large molecular weight polymer is nearly insensitive to the polymer concentration, and primarily determined by the shear rate alone. The prominent microstructural features of these shear-induced transformations are quantified in detail and discussed in light of the competition between interparticle attraction and microscopic shear forces.

Metody kontrolowanej polimeryzacji rodnikowej (CRP) w syntezie kopolimerow poliuretanowych

This paper is a review covering the methods most often applied in the synthesis of polyurethane copolymers of various structures (e.g. block or star-shaped). New Controlled Radical Polymerization (CRP) methods such as Controlled Radical Polymerization using the iniferter technique, Atom Transfer Radical Polymerization (ATRP) and the Surface Initiated Atom Transfer Radical Polymerization (SI ATRP) have been discussed in detail. There has been progress made in recent years in each of these methods allowing for the synthesis of small or large molecular weight polymers, functionalization with various types of terminal groups and the formation of novel products with unique topology (nanotubes, core-shell particles) as well as block or star-shaped copolymers. Specifically, CRP allows for the development of biomedical materials — antimicrobial coatings of controlled thickness or protein-resistant surface layers.

Procyanidin Content of Grape Seed and Pomace, and Total Anthocyanin Content of Grape Pomace as Affected by Extrusion Processing

Grape juice processing by-products, grape seed and pomace are a rich source of procyanidins, compounds that may afford protection against chronic disease. This study was undertaken to identify optimal extrusion conditions to enhance the contents of monomers and dimers at the expense of large molecular weight procyanidin oligomers and polymers in grape seed and pomace. Extrusion variables, temperature (160, 170, and 180 degrees C in grape seed, and 160, 170, 180, and 190 degrees C in pomace) and screw speed (100, 150, and 200 rpm in both) were tested using mixtures of grape seed as well as pomace with decorticated white sorghum flour at a ratio of 30 : 70 and moisture content of 45%. Samples of grape seed and pomace were analyzed for procyanidin composition before and after extrusion, and total anthocyanins were determined in pomace. Additionally, chromatograms from diol and normal phase high-performance liquid chromatography were compared for the separation of procyanidins. Extrusion of both grape by-products increased the biologically important monomer and dimers considerably across all temperature and screw speeds. Highest monomer content resulted when extruded at a temperature of 170 degrees C and screw speed of 200 rpm, which were 120% and 80% higher than the unextruded grape seed and pomace, respectively. Increases in monomer and dimer contents were apparently the result of reduced polymer contents, which declined by 27% to 54%, or enhanced extraction facilitated by disruption of the food matrix during extrusion. Extrusion processing reduced total anthocyanins in pomace by 18% to 53%. Extrusion processing can be used to increase procyanidin monomer and dimer contents in grape seed and pomace. Procyanidins in grape by-products have many health benefits, but most are present as large molecular weight compounds, which are poorly absorbed. Extrusion processing appears to be a promising technology to increase levels of the bioactive low molecular weight procyanidins.

Self-Consistent Field Theory Study of the Effect of Grafting Density on the Height of a Weak Polyelectrolyte Brush

The height of weakly basic polyelectrolyte brushes in the osmotic brush regime is studied as a function of the grafting density using a numerical self-consistent field theory derived from the (semi)grand canonical partition function. The theory is shown to properly account for the local nature of the charge equilibrium and to capture the basic behaviors of polyelectrolyte brushes. On one hand, we find, in agreement with recent experiments, that the scaling of brush height with grafting density can be qualitatively different at intermediate chain lengths than that predicted by basic scaling arguments. This difference is attributed to the relative strength of electrostatic type interactions compared to finite segment size packing constraints. On the other hand, the trend of decreasing brush height with increasing grafting density predicted by the classic scaling analysis is recovered for large molecular weight polymers immersed in a solution of very weak ionic strength.

Influence of Extrusion Processing on Procyanidin Composition and Total Anthocyanin Contents of Blueberry Pomace

Blueberry juice processing by-products are a rich source of procyanidins, which comprise a group of compounds shown to possess numerous health benefits, including protection against coronary heart disease, type II diabetes, and obesity. Most of the procyanidins present in blueberry pomace, however, are large molecular weight compounds that are poorly absorbed and show weak bioactivity compared to the smaller molecular weight monomers and dimers. The objective of our study was to identify optimal extrusion variables to enhance the contents of monomers and dimers at the expense of large molecular weight procyanidin oligomers and polymers. Extrusion variables temperature (160 and 180 degrees C) and screw speed (150 and 200 rpm) were tested using mixtures of blueberry pomace with decorticated white sorghum flour at a ratio of 30 : 70 and 45% moisture content. Extrudates were analyzed for procyanidin composition and total anthocyanin content. Extrusion of blueberry pomace increased the monomer, dimer, and trimer contents considerably at both temperature and screw speeds. The highest monomer content, obtained at 180 degrees C and 150 rpm screw speed, was 84% higher than the nonextruded control. Significantly higher levels of dimer and trimer contents were also obtained under these conditions. Increases in monomer, dimer, and trimer contents apparently were the result of reduced polymer contents, which was approximately 40% lower for samples extruded at 180 degrees C temperature and 150 rpm screw speed. Extrusion processing reduced total anthocyanin contents by 33% to 42% indicating that additional treatments are needed to retain the pigments. These results demonstrate that extrusion processing can be used to increase procyanidin monomer and dimers in blueberry pomace.