Behavior Of Biopolymers Research Articles

Biopolymer and Cation Behavior during WAS Digestion with an AnMBR Process and Their Contribution to Membrane Fouling

Biopolymer and Cation Behavior during WAS Digestion with an AnMBR Process and Their Contribution to Membrane FoulingThis paper addresses a study that was conducted to characterize the behavior of biopolymers and cations and their impact on membrane performance in a pilot AnMBR stabilizing waste activated sludge (WAS). Three AnMBR operating conditions consisting of 15/30 (run 1), 7/15 (run 2) and 7/30 (run 3) day HRT/SRT respectively were evaluated with regard to generation, consumption and/or accumulation of...Author(s)M. DagnewW. ParkerM. BasuvarajS. LissSourceProceedings of the Water Environment FederationSubjectSession 19: Young Professionals: The Industry's Future IIDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2010ISSN1938-6478SICI1938-6478(20100101)2010:4L.1320;1-DOI10.2175/193864710802767254Volume / Issue2010 / 4Content sourceResiduals and Biosolids ConferenceFirst / last page(s)1320 - 1343Copyright2010Word count360Subject keywordscationsbiopolymersfoulinganaerobic membrane bioreactoranaerobic digestion

Multiscale modelling and optimisation strategies for better under-standing of biopolymer mechanical properties: review of recent contributions

Some biopolymers are considered as interesting natural materials for the replacement of oil-based products. Others are known as complex food systems for which texture properties determine the sensory perception. For both applications, the need to understand the mechanical behavior of biopolymers is essential. Control of texture, improvement of mechanical performance are some of the issues for which a growing research interest is noticed. The understanding of the mechanical properties cannot be considered without valuable information about the microstructure. For such materials, structural heterogeneities, which affect the behavior, appear to be dependent on several interacting scales. It is the aim of this work to shed more light on the possibility to use optimization techniques to either identify or optimize the mechanical properties of starch-based materials at different scales. We take the example of the starch cellular material, which proved to be necessitating a multiscale approach. The context of the present study is related to the investigation of elasticity behavior of cellular materials.

Study of the structure of wood-related biopolymers by sorption methods

The potentialities of different vapour sorption methods are analized for the investigation of the microstructure of wood sorbents (wood, cellulose and lignin) as a particular case of biopolymers. There are two important distinctions in the sorption behaviour of biopolymers from traditional rigid sorbents, namely, the dependence of the characteristics of the porous structure on the thermodynamic properties of the sorbate, and the manifestation of the sorption hysteresis over the whole region of the sorption–desorption isotherm. The reason for these distinctions is the low rigidity (low values of modulus of elasticity) of biopolymers, hence, their considerable deformability under the action of sorption forces, resulting in the cleavage of interstructural bonds. This process, manifesting itself phenomenologically as swelling, depends on the activity of the sorbate and results in the appearance of porosity and a new surface. The criterion for the activity of the sorbate is close values of the solubility parameters of the polymer and the sorbate. Inert substances are adsorbed on the surface of large morphological formations and characterise the intact structure of the sorbent, while active sorbates cause the swelling of these formations and penetrate them, which enables a study of the microstructure of sorbents. In the desorption process, the cleaved bonds are restored, blocking a part of the sorbate in the polymer’s structure, which results in the appearance of sorption hysteresis, not connected directly with the porous structure of the sorbent.

Probing interactions by means of pulsed field gradient nuclear magnetic resonance spectroscopy

Molecular self-diffusion coefficients (D) of species in solution are related to size and shape and can be used for studying association phenomena. Pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy has been revealed to be a powerful analytical tool for D measurement in different research fields. The present work briefly illustrates the use of PFG-NMR for assessing the existence of interactions in very different chemical systems: organic and organometallic compounds, colloidal materials and biological aggregates. The application of PFG-NMR is remarkable for understanding the role of anions in homogenous transition metal catalysis and for assessing the aggregation behaviour of biopolymers in material science.

Self-Organization in Solutions of Stiff-Chain Amphiphilic Macromolecules

Conformational properties of amphiphilic stiff-chain macromolecules in concentrated solutions in poor solvent have been studied via computer modeling. We have found that the conformational state of macromolecules in such systems depends on the macromolecular stiffness and on the way the solution has been prepared. Thus, if the concentration of globules increased from a very diluted solution, the globules remain stable, independent of the macromolecular stiffness, and do not aggregate even in concentrated solutions. On the other hand, if the solvent quality is gradually decreased in a solution with a concentration much larger than that of a semidilute solution, then relatively flexible chains form separate globules, whereas semirigid macromolecules tend to aggregate and form braid-like conformations. The results obtained agree with the published experimental data and can be used for directed synthesis of macromolecules modeling the behavior of biopolymers.

Creep behaviour of biopolymers and modified flax fibre composites

Creep-recovery behaviour of natural fibre–biopolymer composite systems, poly(lactic acid)–flax and poly(hydroxybutyrate)–flax, with various additives, was quantitatively resolved into elastic deformation, viscoelastic deformation and viscous flow. Comparative interpretation of creep behaviour between composites with different additives was presented and the factors that influenced creep were identified. In comparison with unmodified composites, the additive that proved to be the most effective in reducing creep was thiodiphenol, which formed hydrogen bonds at the interface of polymer and fibre; while a decrease was observed with tributyl citrate, a plasticiser. The suppression of creep in the composites with thiodiphenol was due to reduction in the viscous flow contribution to total creep and a significant increase in both the elastic and viscoelastic deformation. The reduction in creep for the plasticised composites was mainly attributed to a reduction in the viscous flow contribution and an increase in the viscoelastic deformation. The elastic component did not show any changes from the unmodified composite. With hyperbranched polyester, a toughness modifier, an increase in permanent strain and reduction in the recoverable strain were attributed to the hyperbranched molecules being able to easily flow past each other as they cannot form chain entanglements due to their globular structure.

Manipulating Biopolymer Dynamics by Anisotropic Nanoconfinement

How the geometry of nanosized confinement affects dynamics of biomaterials is interesting yet poorly understood. An elucidation of structural details upon nanosized confinement may benefit manufacturing pharmaceuticals in biomaterial sciences and medicine. The behavior of biopolymers in nanosized confinement is investigated using coarse-grained models and molecular simulations. Particularly, we address the effects of shapes of a confinement on protein-folding dynamics by measuring folding rates and dissecting structural properties of the transition states in nanosized spheres and ellipsoids. We find that when the form of a confinement resembles the geometrical properties of the transition states, the rates of folding kinetics are most enhanced. This knowledge of shape selectivity in identifying optimal conditions for reactions will have a broad impact in nanotechnology and pharmaceutical sciences.

Autoxidation of Medium Chain Length Polyhydroxyalkanoate

Polyhydroxyalkanoates (PHAs) are a class of biopolymers that are currently the subject of intensive research for various applications (packaging, consumer products, medical applications, etc.). It is known from synthetic polymers that all plastic materials show more or less pronounced autoxidation (aging induced by UV radiation, temperature, heavy metal ions, etc.). There is less knowledge as yet regarding the autoxidation behavior of biopolymers. The autoxidative behavior of medium chain length poly[(R)-3-hydroxyalkanoate] (mcl-PHA) was therefore investigated. mcl-PHA (co)polymers with amounts of 0, 10, 50, and 75 mol % of olefinic side chains with terminal double bonds were tempered at 60 degrees C in air for 3 months. After 1, 2, 4, 8, and 12 weeks, samples were removed and analyzed for changes in chemical and physical properties by sol-gel analysis (Soxhlet extraction), size exclusion chromatography (SEC), infrared analysis (IR), and gas chromatography/flame ionization detection (GC/FID). It became apparent that the content of double bonds greatly influences the autoxidation of mcl-PHA. A low amount of unsaturated moiety (0 and 10 mol %) resulted in chain scission, whereas samples with 50 and 75 mol % olefinic side chains showed cross-linking and became insoluble after a few weeks. Kinetic data of oxidation behavior were investigated by performing isothermal DSC experiments at elevated temperatures. The kinetic data combined with the experiment enabled the gelation time to be predicted and the shelf-life of mcl-PHA to be estimated. Because of the detected sensitivity of mcl-PHA regarding autoxidation, it is recommended that these biopolymers should be stored cold (at least -5 degrees C) and in an inert gas atmosphere or stabilized by suitable additives (antioxidants).

Synthesis and characterization of pendant carboxylic acid functional poly(lactic acid) and poly(lactic acid‐co‐glycolic acid) and their drug release behaviors

AbstractThe carboxylic acid functionalized biodegradable aliphatic polyesters were prepared by ring‐opening polymerization of L‐lactide and glycolide with 2,2′‐bis(hydroxymethyl propionic acid) (HMPA) as an initiator. The polymers were characterized by FT‐IR, 1H‐NMR and gel permeation chromatography (GPC). Molecular weights of homopolymers and copolymers ranged from 0.28 × 104 to 11 × 104 and decreased with increasing weight fraction of HMPA in the feed. Moreover by changing the HMPA content, the solubility and degradation behavior of resulting polymers could be varied. Environmental scanning electron microscopy (ESEM) studies revealed that the microspheres were spherical in shape and had a smooth surface texture. For the investigation of drug release behavior of biopolymers, Lidocain was used as a model ionic drug. It was observed that an increase in drug loading reduces the encapsulation efficiency. After the initial burst, the release rate of the drug increased with time, with most of the drug released within 15 days. Copyright © 2005 John Wiley & Sons, Ltd.

Liquid crystalline biopolymers: A new arena for liquid crystal Research

Although discovered almost a century ago, it was until the mid sixties that liquid crystals were just regarded as curious materials that exhibited unusual properties as they melted from a solid to a liquid state of matter. Today liquid crystals (LC) have become the basis of many advanced technologies. They are extensively used in displays of wristwatches, calculators, laptop computers, aircraft and many appliances and have newer applications in flat-panel television, large switchable privacy windows, optical computing and optical devices for communication networks. The future of liquid crystals is envisaged to look even more promising because of their important role in biology and their hitherto not fully discovered potential for applications in food, agriculture, medicine, high performance materials development and other industrial and biotechnological processes. Major classes of biological compounds including lipids, proteins, carbohydrates and nucleic acids all have been found to exist in various liquid crystalline phases in vivo as well as in vitro under well-defined conditions. Their liquid crystalline structure is envisaged to have a very important role in their biological functions and self assembly processes. In order to get a better insight into biological processes at supramolecular level it is very important to have, in depth, knowledge of properties of liquid crystalline materials. This paper gives a brief introduction to liquid crystals and reviews literature on liquid crystalline behaviour of biopolymers both in vitro and in vivo in relation to their implications in the fields of biology, medicine and material science.

Constitutive analysis of the nonlinear viscoelastic properties of cellulosic fiber gels produced from corn or oat hulls

The evaluation and development of validated models for the nonlinear viscoelastic (VE) behavior of materials is an important area of research, which has impact on a number of industrial processes including those in the food industry. Various nonlinear VE models have been developed over the years and evaluated for petroleum-based polymers, however, our understanding of the nonlinear VE behavior of biopolymers of industrial import lags our understanding of synthetic polymers. In the work reported herein, the nonlinear VE behavior of several cellulosic fiber gels prepared from either corn or oat hulls were investigated. The rheological properties were measured using a Rheometrics Series IV controlled-strain rheometer equipped with a cone and plate fixture. The measurements were conducted at 23±0.1 °C. The rheological data were interpreted using a strain separable K-BKZ type (Wagner) model with a damping function evaluated from stress relaxation data. The Wagner model was found to provide an accurate description of the rheological behavior of the suspensions.

Semiflexible random A–B block copolymers under tension

In this paper we explore the conformational properties of random A–B block copolymers with semiflexible segments in a constant force field as a model of the behavior of biopolymers under tension. The degree of semiflexibility of individual blocks, which is characterized by a persistence length l, may range from values that correspond to complete flexibility of the block to values that correspond to nearly complete rigidity. The distribution of blocks is described by a two-state Markov process that generates the statistics governing the process of living polymerization in the steady state. Force-extension curves for this model of the polymer are calculated as an average over the chains conformations (which are described by a finitely extensible Gaussian model), as well as over both quenched and annealed distributions of the sequence of A and B blocks along the chain backbone. The results are sensitive to the nature of the sequence distribution: in the annealed case, the force-extension curves are sigmoidal for essentially all values of the parameters that characterize the conformational properties of the A and B blocks and their statistical correlations, while in the quenched case, the curves exhibit plateau regions that are reminiscent of various kinds of transitions in proteins and DNA.

Prediction of the nonlinear transient and oscillatory rheological behavior of flour suspensions using a strain-separable integral constitutive equation

The evaluation and development of validated models for the nonlinear viscoelastic (VE) behavior of materials is an important area of research, which has impact on a number of industrial processes including those in the food industry. Various nonlinear VE models have been developed over the years and evaluated for petroleum-based polymers; however, our understanding of the nonlinear VE behavior of biopolymers of industrial import lags our understanding of synthetic polymers. In the work reported herein, the nonlinear VE behaviors of defatted oat flour, oat bran, barley flour, and oat flour suspensions were investigated. The rheological properties were measured using a Rheometrics Series IV controlled-strain rheometer equipped with a cone and plate fixture. The measurements were conducted at 23±0.5°C. The rheological data were interpreted using a strain-separable K-BKZ type (Wagner) model with a damping function evaluated from stress relaxation data. The Wagner model was found to provide an accurate description of the rheological behavior of the suspensions produced from defatted oat flour, barley flour, and oat bran. For suspensions produced from oat flour, the model predictions deviated from the experimental data to a greater degree than the other materials.

Structure and conformational behavior of biopolymers by density functional calculations employing periodic boundary conditions. I. The case of polyglycine, polyalanine, and poly-alpha-aminoisobutyric acid in vacuo.

Fully quantum mechanical calculations exploiting periodic boundary conditions (PBC) have been applied to the study of four different regular structures (alpha- and 3(10)-helix, fully extended and repeated gamma-turns) of the infinite polypeptides of glycine, alanine, and alpha-aminoisobutyric acid (Aib) in vacuo. alpha-Helix is predicted to be the most stable conformer for polyalanine and polyglycine, being stabilized over the 3(10)-helix mainly by more favorable dipole-dipole interactions. Contrary to previous suggestions, steric effects and hydrogen-bond strengths are comparable for both helix structures. 3(10)-Helix is preferred for poly-Aib, since in this case alpha-helix is strongly distorted due to unfavorable intrachain repulsions. Extended structures and repeated gamma-turns are much less stable than helix structures for all of the polypeptides examined, mainly due to the absence of favorable long-range interactions. The optimized geometries are in good agreement with the available experimental data and reveal a remarkable dependence on the nature of the residue forming the polypeptides; at the same time the electronic and structural parameters of each residue strongly depend on the secondary structure of the polypeptides.

Assessing the effect of conformational averaging on the measured values of observables.

Experiment and computer simulation are two complementary tools to understand the dynamics and behavior of biopolymers in solution. One particular area of interest is the ensemble of conformations populated by a particular molecule in solution. For example, what fraction of a protein sample exists in its folded conformation? How often does a particular peptide form an alpha helix versus a beta hairpin? To address these questions, it is important to determine the sensitivity of a particular experiment to changes in the distribution of molecular conformations. Consequently, a general analytic formalism is proposed to determine the sensitivity of a spectroscopic observable to the underlying distribution of conformations. A particular strength of the approach is that it provides an expression for a weighted average across conformational substates that is independent of the averaging function used. The formalism is described and applied to experimental and simulated nuclear Overhauser enhancement (NOE) and 3J-coupling data on peptides in solution.

Optical Traps as Force Transducers: The Effects of Focusing the Trapping Beam through a Dielectric Interface

The use of optical forces generated by a focused laser beam for manipulating single polymer chains and colloidal particles has begun to receive increasing attention in polymer and colloid science and in biophysics. Devices based on such optical traps are increasingly used for probing the elasticity of single polymer chains and for studying the structure and mechanical behavior of biopolymers and their relation to biological activity. Colloidal forces and viscoelastic behavior of the suspending fluids can also be examined through the use of optical traps as force transducers and from the dynamics of optically bound probe particles. Such applications require a precise understanding of the trap potential and its dependence on the distance between the trap center and the glass/liquid interfaces that exist in experimental arrangements. This paper addresses some of the issues relevant to the above class of applications of optical traps using wave optics calculations. It is shown that the use of simple geometric...

Effects of electrostatic and hydrophobic interactions on the chromatographic behavior of biopolymers in HPLC columns

AbstractThe effect of electrostatic and hydrophobic interactions on the chromatographic behavior of biopolymers with the use of chemically bonded silica‐based HPLC columns and aqueous buffered mobile phases containing neutral salts in a wide range of concentration is discussed. Two columns packed with stationary phases appositely designed for biopolymer HPLC in size exclusion and anion exchange mode, respectively, are examined. Experimental data are evaluated by plotting the measured isocratic elution volumes of several standard proteins of different isoelectric point against the salt concentration in the mobile phase. Depending on the concentration and nature of salt, both columns exhibit different domains where either sieving effect or electrostatic or hydrophobic interactions are predominant. At sufficiently low salt concentrations electrostatic interactions are predominant leading to either increasing or decreasing elution volumes depending on the sign of the charges on the stationary phase and the protein, respectively. On the other hand, at high salt concentrations of a salt with sufficiently high molal surface tension increment proteins may be retained by hydrophobic interactions.

Studies on the correlation of chromatographic behaviour of biopolymers between reversed-phase and hydrophobic interaction chromatography. Testing the stoichiometric displacement between biopolymer and displacing agent

One hundred and one sets of retention data obtained from twenty types of chromatographic systems with seventeen kinds of biopolymers in both reversed-phase and hydrophobic interaction chromaoography were used to test the broad applications of stoichiometric displacement model of retention. We also investigated the linear relationship between the stoichiometric displacement parameter Z and molecular weight of proteins and found out that it really depends on the changes in the molecular conformation or the completeness of losing quarternary or tertiary structure of proteins during the chromatographic process.

Prediction of the rotational diffusion behavior of biopolymers on the basis of their solution or crystal structure

Two low structure-resolution methods are proposed for prediction of rotational diffusion parameters. The indirect procedure is based on the structure of a molecule in solution or in crystal, and uses the structure parameters of radius of gyration, and low-resolution molecular surface and volume, determined from measured or theoretically calculated small-angle x-ray scattering intensities, to estimate a frictional equivalent ellipsoid of revolution. The direct method starts mainly from the crystallographic structure of a molecule and calculates the triaxial inertia equivalent ellipsoid, experimentally calibrated by translation diffusion data, to simulate the frictional behavior. The predicted harmonic mean of the rotational correlation times of compact globular macromolecules with molar masses of 14,000-65,000 g/mol agree with experimental results within the error limits. The prediction method is recommended for expert systems in structure research and for detection of internal protein flexibility or marker mobility by nmr and electron paramagnetic resonance experiments.

Biopolymer determinations by high-performance liquid chromatography with low angle laser light scattering photometry

Low angle laser light scattering spectrophotometry (LALLS) can be successfully interfaced with modern high-performance liquid chromatography (HPLC) for the separation and determination of protein biopolymers. Most, if not all, modern HPLC modes may be compatible with on-line LALLS instrumentation. Significant information about biopolymer behavior, conformational changes, aggregate formation, adduct formation, degradation and cleavage, and other changes in physical structure can be derived by on-line LALLS measurements. Methods for successfully using current commercial LALLS instrumentation in modern HPLC biopolymer separations are described, and applications from the literature are mentioned. Suggestions are presented for future improvements in interfacing HPLC biopolymer separations with on-line LALLS, as well as refractive index (RI, dn) and concentration (UV, dc), measurements. Approaches are suggested for measuring the excess Rayleigh factor (R θ exc), change in refractive index (dn), change in concentration (dc), and deducing the specific refractive index increment (dn/dc) and absolute molecular weight (M w ave) for each incremental elution point.