Biopolymers In Aqueous Solution Research Articles

Nature as Resource. Thermodynamic characterization of natural and synthetic polymers and their sequestering ability towards some bivalent metal cations

The aim of this paper is to enhance the knowledge on the behaviour and thermodynamic properties of natural and synthetic biopolymers in aqueous solutions. The acid-base properties of Carrageenan (Car), Xanthan gum (XG), Hydroxyethyl cellulose (HEC), Carboxymethyl cellulose (CMC), Acusol 445™ (Sol), Monopropylene glycol (MPG) and Polyethylene glycol (PEG) have been studied by potentiometric technique in NaNO3(aq), at I = 0.15 mol dm−3 and T = 298.15 K. In some cases, the protonation constants have been determined at different ionic strengths, and the dependence on ionic strength has been modelled by a Debye-Hückel type equation. The binding ability of the different polymers has been investigated towards Ca2+, Zn2+ and Sn2+ and, different speciation models have been obtained. For Acusol 445™, the weak interactions with Na+ and K+ have been determined. The effect on the complexing ability of a secondary inorganic ligand, the fluoride, has been evaluated on Carboxymethyl cellulose and Acusol systems; the formation of ternary mixed complexes with a significant increasing stability with respect the binary species has been obtained.The sequestering ability of the polymers towards the metal cations has been evaluated by means the empirical parameter pL0.5.

Simultaneous adsorption and reduction of hexavalent chromium on the poly(4-vinyl pyridine) decorated magnetic chitosan biopolymer in aqueous solution

Poly(4-vinyl pyridine) decorated magnetic chitosan biopolymer (VMCP), as an absorbent and reductant, was prepared and used to remove hexavalent chromium (Cr(VI)) from aqueous solution. Compared with undecorated magnetic biopolymer, VMCP exhibited significantly improved removal performance under identical experimental conditions. The kinetics, isotherms, and thermodynamics of Cr(VI) adsorption onto VMCP were investigated. Results demonstrated that the maximum monolayer adsorption capacity of VMCP was 344.83 mg/g, which was considerably higher than most reported adsorbents. The mechanism for Cr(VI) removal was explored based on XPS and FTIR analyses. The main mechanisms were concluded to be Cr(VI) adsorption onto the positively charged VMCP surface and the reduction of Cr(VI) to Cr(III), followed by coordination between Cr(III) and N atoms. The easy regeneration, satisfactory reusability, and remarkable performance in column tests revealed the high potential of VMCP in treating Cr(VI)-contaminated water.

Evaluation of the antibacterial activity of a cationic polymer in aqueous solution with a convenient electrochemical method.

Quaternized chitosan is a cationic biopolymer with good antibacterial activity, biocompatibility, and biodegradability, and it has been widely applied in many fields. We have developed a convenient method to evaluate the antibacterial activity of hydroxypropyltrimethylammonium chloride chitosan (HACC) with a nonionic surfactant poloxamer in aqueous solution by monitoring the change of the oxidation peak current in cyclic voltammetry. Increasing values of the oxidation peak current were positively correlated with the antibacterial activity of HACC-poloxamer solutions. Optical microscope images, the zeta potential, and fluorescence spectroscopy showed that the aggregation state of HACC-poloxamer was related to the ratio of the two polymers and also to the antibacterial activity and oxidation peak current. At an HACC-to-poloxamer ratio of 1:0.75, the maximum surface charge density and the smooth edge of HACC-poloxamer aggregates can accelerate diffusion in aqueous solution. It is expected that this convenient method can be applied for a quick evaluation of the antibacterial activity of cationic biopolymers in aqueous solution. Graphical Abstract The cyclic voltammograms of MB in HACC/poloxamer solution, and the antibacterial efficiency against S. aureus after incubated with HACC (a) and 1/0.75 of HACC/poloxamer (b).

Characterization and rheological behaviour analysis of the succinoglycan produced by Rhizobium radiobacter strain CAS from curd sample

An exopolysaccharide (EPS) producing strain CAS grown in a Bushnell Haas medium was isolated from curd sample and identified as Rhizobium radiobacter CAS. The biopolymer was duly characterized by FT-IR and NMR spectroscopy and was found to be composed of glucose and galactose in a molar ratio of 6.99:1 as confirmed by HPAEC; thus depicting it to be succinoglycan type exopolysaccharide. In addition, conceivable presence of one succinate and two acetate groups of succinoglycan was estimated using 1H NMR analysis by specific signal integration. Furthermore, as a documented fact, the insights into the rheological behaviors portray phenomenal influences in food, cosmetics and pharmaceutical industries as thickening, gelling, stabilizing and emulsifying agent. However, this piece of information has remained unnoticed from the existing literature. Thus, in the present study the rheological properties of succinoglycan type biopolymer in aqueous solution were systematically investigated. The flow behaviour testing in an aqueous solution verified its pseudoplastic character and higher apparent viscosity. Furthermore, study on its potential strength and tolerance in various thermal conditions, cation salts, and pH has been studied in depth. Such a study can provide a thorough guidance on the rheological behaviour of the biomaterial and thus impart significant insights into postulating its application spectrum into food, cosmetics and pharmaceutical industrial sectors. The present study is thus, one of its kinds which decipher the complete rheological behavioural portrait.

Studies on self‐assembly interactions of proteins and octenyl succinic anhydrate (OSA)‐modified depolymerized waxy rice starch using rheological principles

ABSTRACTDynamic tests (23 °C, pH ∼ 7.0) yielding relaxation times, λ, as a function of frequency and polymer concentration were performed to assess self‐assembly characteristics of biopolymers in aqueous solution. Reduction of λ‐values (slope) up to a critical frequency value (CFV) helps characterize structure formation. Proteins and octenyl succinic anhydrate (OSA)‐modified depolymerized waxy rice starch (DWxRc) show a well‐defined λ‐slope at all concentrations. Except for whey protein isolate (WPI, 0.184 g/L) and 7% OSA‐modified DWxRc (1.84 g/L), the λ‐values of the solutions are comparable (P > 0.05), indicating similar structures. Self‐assembly interaction of α‐lactalbumin (3.68 g/L) with OSA‐modified polysaccharides is observed with 18.4 g/L of 7% OSA‐modified DWxRc (CFV of 0.08 Hz), while WPI (3.68 g/L) exhibits self‐assembly with all polysaccharides and concentrations. Transmission electron microscopy (TEM) of electrostatically precipitated proteins alone or in combination with OSA‐modified polysaccharides confirms that λ−slope and CFV values relate to shape, size, and shear stability of the assembled structures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43603.

Computational study of polymorphic structures of α- and β- chitin and chitosan in aqueous solution

Chitin is a natural biopolymer and the second most abundant after cellulose. This polysaccharide can be found in the biomass in different polymorphic forms. Chitosan is one of the most important derivatives obtained from the deacetylation of chitin. In this work, Molecular Dynamics simulations of chitin and chitosan nanoparticles enabled us to evaluate their different conformation and solubility properties. The Molecular Dynamics simulations show that the arrangement of the chains of chitin and chitosan significantly affects the structural behavior of these biopolymers in aqueous solution.

Study of interactions between octyl-β-d-glucopyranoside and the hydroxyethyl-cellulose biopolymer in aqueous solution

(Surfactant+polymer) systems play an important role in drug delivery. They control the drug release rate by improving solubility, minimizing degradation, contributing to the reduction of toxicity and facilitating drug administration. Physicochemical properties of surfactant/polymer systems used in controlled drug release are affected by the composition of the mixture. The study of the physicochemical behavior of these mixtures allows the design of more suitable drug pharmaceutical formulation according to its chemical structure. In this paper, critical micelle concentration (CMC), saturation concentration (C2), critical aggregation concentration (CAC) and thermodynamic parameters, such as enthalpy (ΔH), Gibbs free energy (ΔG) and the temperature multiplied by entropy (TΔS) for the demicellization process were determined by isothermal titration calorimetry (ITC), for octyl-β-d-glucopyranoside (OGP) and hydroxyethyl-cellulose (HEC) aqueous solutions in order to construct a phase diagram suitable for the study of the interactions in each region and to choose the appropriate system for drug delivery. The interpretation of the results is supported by the analysis of particle size measurements by dynamic light scattering (DLS).

Effects of some salts on H2O as probed by a thermodynamic signature of glycerol: towards understanding the Hofmeister effects (VII)

The generality of the Hofmeister effects has been questioned of late, and doubts have been cast over their importance in understanding the specific ion effects on the chemistry and physics of biopolymers in aqueous solutions. Recent experimental evidence from modern non-linear spectroscopies points mostly to the direct interaction between the ion and the biopolymer in question that is more important for understanding the Hofmeister effects. On the other hand, our own contribution by higher order thermodynamical studies indicated that the effects of ions on H2O itself may not be denied all together. Namely, we devised a methodology whereby the effect of an ion on H2O is characterized by two orthogonal indices, hydrophobicity and hydrophilicity, by using a third order thermodynamic signature of hydrophobic 1-propanol (1P) as a probe, the 1P-probing methodology. The results indicated that the common anion ranking could be understood in terms of two indices, hydrophobicity and hydrophilicity of an individual ion. In the present work, we make an attempt at probing the effects of the same ions on H2O by a typical hydrophile, glycerol (abbreviated as Gly in this article). Compared with the results of the 1P-probing methodology, we seek to determine how hydrophiles would react to the subtle modification of H2O caused by the presence of an ion, since biopolymers are large amphiphiles with hydrophobic and hydrophilic surfaces. The results indicate that the Gly-probe is much less sensitive than the 1P-probe. We suggest therefore that it is the hydrophobic moieties of biopolymers that mainly give more conspicuous response to the modified H2O by the presence of an ion.

Viscometric study of pectin. Effect of temperature on the hydrodynamic properties

Hydrodynamic properties are important parameters affecting the performance of pectin. This polysaccharide is used as a thickening and gelling agent in food and pharmaceutical industries. The most common and economical of the hydrodynamic properties is the determination of viscosity, in which are determined the intrinsic viscosity and the diffusion coefficient. They indirectly measure the molecular weight ( M w); hydrodynamic radius ( R H); number of Simha, ( ν ( a/ b) ); Perrin parameter ( P); Scheraga–Mandelkern parameter ( β); and Flory parameters ( ϕ 0 and P 0). All the hydrodynamic parameters are dependent on temperature. Normally these parameters are reported at a temperature of 25 °C, which limits their application to different temperatures. This work studies pectin dependence on temperature, finding that this biopolymer in aqueous solution presents a conformation of rod-like with ν ( a/ b) = 10.5, and a value from 0.8232 to 0.8129. Pectin behavior in this system indicates that it behaves like a colloidal particle that tends to compact with increasing temperature ( R H decrease). The molecular weight calculated for pectin is 180,000 g/mol. Mark–Houwink–Sakurada (M–H–S) equation constants, a and k, for pectin in water solvent-temperature systems have been already reported.

Electrophoretic deposition of chitosan

The electrophoretic deposition (EPD) of chitosan on metallic substrates was investigated. The electrophoretic mobility of the natural biopolymer in aqueous solution as a function of pH was studied. Because the protonation/deporotonation of chitosan is pH-dependent, the electrophoretic mobility and deposition rate is shown to increase with increasing pH from 2.9 to 4.1. The film growth rate is estimated to vary in the range 0.02–0.08 µm/s depending on the pH value. At high growth rates (> 0.05 µm/s), a porous film is obtained due to hydrogen entrapment. The EPD method developed here is applicable for the surface modification of metal implants by chitosan to develop novel bioactive coatings.

Effect of carboxymethyl cellulose concentration on rheological behavior of milk and aqueous systems. A creep and recovery study

AbstractCarboxymethyl cellulose (CMC) is an anionic polysaccharide used mainly as stabilizer and thickener agent. The purpose of this study was to investigate the effect of CMC concentration on viscoelasticity of dairy and aqueous model systems through the analysis of creep and recovery tests. The viscoelastic properties of different concentrations of CMC (0.75, 1.00, 1.25, and 1.50% w/w) in two milk systems (skimmed milk and whole milk) were compared with those of the same concentration of biopolymer in aqueous solution. Creep curves were fitted to a six parameter mechanical model (Burger + Kelvin‐Voigt), whereas an empirical equation was used for recovery. The creep and recovery properties of samples were clearly affected by both the type of dispersing media and the CMC concentration. The whole‐milk system was more elastic than both the biopolymer (CMC) aqueous solution and the skimmed‐milk sample, indicating that in whole‐milk samples some new interactions could take place between macromolecules. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Mixing Schemes in a Urea−H2O System: A Differential Approach in Solution Thermodynamics

The excess partial molar enthalpies of urea (UR), H U R (E ), were experimentally determined in UR-H 2O at 25 degrees C. The H U R (E ) data were determined accurately and in small increments in the mole fraction of UR, x U R , up to x U R approximately 0.22. Hence it was possible to evaluate one more x U R -derivative graphically without resorting to any fitting function, and the model-free UR-UR enthalpic interaction, H U R- U R (E ), was calculated. Using previous data for the excess chemical potential, mu U R (E ), the entropy analogue, S U R- U R (E ), was also calculated. The x U R -dependences of both H U R- U R (E ) and S U R- U R (E ) indicate that there is a boundary at x U R approximately 0.09 at which the aggregation nature of urea changes. From the results of our earlier works, we suggest that a few UR molecules aggregate at x U R approximately 0.09, while the integrity of H 2O is retained at least up to x U R approximately 0.20. Together with the findings from our previous studies, we suggest that in the concentration range x U R < 0.22, UR or its aggregate form hydrogen bonds to the H 2O network, reducing the degree of fluctuation characteristic to liquid H 2O. However, up to at least x U R = 0.20 the hydrogen bond network remains intact. Above x U R approximately 0.22, the integrity of H 2O is likely be lost. Thus, in discussing the effect of urea on H 2O and in relating it to the structure and function of biopolymers in aqueous solutions, the concentration region in question must be specified.

An efficient 1H/ 31P double-resonance solid-state NMR probe that utilizes a scroll coil

The construction and performance of a scroll coil double-resonance probe for solid-state NMR on stationary samples is described. The advantages of the scroll coil at the high resonance frequencies of 1H and 31P include: high efficiency, minimal perturbations of tuning by a wide range of samples, minimal RF sample heating of high dielectric samples of biopolymers in aqueous solution, and excellent RF homogeneity. The incorporation of a cable tie cinch for mechanical stability of the scroll coil is described. Experimental results obtained on a Hunter Killer Peptide 1 (HKP1) interacting with phospholipid bilayers of varying lipid composition demonstrate the capabilities of this probe on lossy aqueous samples.

Role of the Coulombic Interaction in Ligand-Induced Biopolymer Aggregation

The interaction mechanisms responsible for the binding between metal complexes and biopolymers in aqueous solution, as well as the consequent aggregation process of biopolymers themselves, involve many factors, from geometrical aspects and hydrophobic contributions, as examples, to the electrostatic potential. In this paper aqueous solutions of a polynucleotide, polyadenylic acid (PolyA), which mimics the helix arrangement of RNA or single-stranded DNA but has a simpler structure, are used as a model system. The role of the electrostatic interactions in the binding process between some platinum(II) complexes and PolyA and in the aggregation among PolyA molecules is investigated, by means of elastic and quasielastic light scattering and electrophoretic mobility. The results show that the presence of large, planar aromatic moiety in the dicationic platinum(II) complexes is essential for the binding with PolyA and suggest that the consequent lowering of the local electrostatic barrier between PolyA molecules can be involved in triggering the aggregation process.

Chemically Sensitive Field‐Effect Transistors and Chemiresistors: New Materials and Device Structures

AbstractElectronic sensor technology remains of widespread and intense interest. There are compelling needs to detect chemical species ranging from small molecules dispersed in the gas phase to complex biopolymers in aqueous solution. This review describes some recent advances in three main areas: chemically sensitive resistors (chemiresistors, CRs) including inorganic and organic based devices, field effect transistors (FETs) with semiconducting layers and/or gates with chemical sensitivity, and sensors based on the differential conductivity of nanotubes and nanowires. Results reported in the last two to three years are emphasized, highlighting some current trends in the development of sensors for applications such as diagnostics, process monitoring, and security.

Ultrasonic and viscometric investigations of a poly(vinyl alcohol)-dextran mixture in aqueous solution

Ultrasonic spectroscopy provided a powerful, efficient, and reliable tool for a number of investigations, including those of polymer solution dynamics, molecular interaction, and the miscibility and compatibility of biopolymers in aqueous solutions. Ultrasonic velocity and related acoustic parameters were measured as a function of the concentration of poly(vinyl alcohol) (PVA), dextran, and a PVA–dextran mixture in water with the resonance method at a frequency of 3 MHz over a temperature range of 20–50°C. From the comparative results of sound velocity, density, adiabatic compressibility, acoustic impedance, and viscosity relaxation time as a function of temperature and concentration, the mode of interaction and the compatibility and miscibility between the two biologically active macromolecules were probed and were considerable at all concentrations and temperatures because of crosslinking via hydrogen bonding involving the hydroxyl groups of both of the biomacromolecules. The interpretations of the acoustic results were confirmed by the intrinsic viscosities of the ternary systems. The significant interaction and compatibility of these biopolymers should lead to the development of pharmaceutically active molecules. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3196–3201, 2003

In Silico Modeling and Conformational Mobility of DNA Duplexes

The review is focused on issues of transferability of the context-sensitive conformational characteristics of DNA estimated from crystallographic structural data on the DNA in aqueous solution. The state of the art in molecular dynamics of charged biopolymers in aqueous solution is covered. Elaboration of expedient force fields and algorithms of calculating long-range electrostatic interactions and solving combined equations of atomic motion have made it possible to generate stable nanosecond trajectories of thermal atomic motion of the biopolymer in aqueous solution in the presence of counterions and salt ions over reasonable time. Tools for analyzing the atomic statistical trajectories of DNA duplexes in aqueous solution to infer context-dependent conformational dynamic characteristics are discussed together with advances in simulating the mechanisms of global axial bend in DNA duplexes. These techniques allow one to consecutively analyze relationships between the contextual composition of the duplex and the basic modes of essential motions, their amplitude and extent of fluctuation. Development of satisfactory methods for estimating the free energy of biopolymer conformations in solution permits qualitative assessment of the conformational thermodynamic stability of biopolymers and their complexes.

Methods of computer modeling and conformational mobility of DNA duplexes

The review is focused on issues of transferability of the context-sensitive conformational characteristics of DNA estimated from crystallographic structural data on the DNA in aqueous solution. The state of the art in molecular dynamics of charged biopolymers in aqueous solution is covered. Elaboration of expedient force fields and algorithms of calculating long-range electrostatic interactions and solving combined equations of atomic motion have made it possible to generate stable nanosecond trajectories of thermal atomic motion of the biopolymer in aqueous solution in the presence of counterions and salt ions over reasonable time. Tools for analyzing the atomic statistical trajectories of DNA duplexes in aqueous solution to infer context-sensitive conformational dynamic characteristics are discussed together with advances in simulating the mechanisms of global axial bend in DNA duplexes. These techniques allow one to consecutively analyze relationships between the contextual composition of the duplex and the basic modes of essential motions, their amplitude and extent of fluctuation. Development of satisfactory methods for estimating the free energy of biopolymer conformations in solution permits qualitative assessment of the conformational thermodynamic stability of biopolymers and their complexes.

Influence of gelation on particle shape in sheared biopolymer blends

The morphology of biopolymer droplets gelled under shear as the dispersed phase of a two-phase mixture of biopolymers in aqueous solution (or “biopolymer blend”) was investigated experimentally. The process involves shearing the liquid biopolymer blend either at a steady stress till gelation, for creation of ellipsoidal gelled particles, or a stress step-up process for creation of high aspect ratio particles. The resulting particle shapes are analyzed and compared against models for affine deformation conditions [Janssen (1997)] and steady shear conditions [Maffetone and Minale (1998)]. Although they are only strictly valid for Newtonian fluid phases, application of these models to a situation where one phase is gelling, has provided insight into the morphological changes occurring in the shear-gelation process.

Molecular structure and interaction of biopolymers as viewed by Fourier transform infrared spectroscopy: model studies on β-lactoglobulin

Fourier transform absorption infrared spectroscopy is a powerful and versatile tool used to determine the molecular structure of biomolecules. This technique is now widely used in biochemistry to study the conformation of biopolymers in aqueous solutions and complex systems. However, its enormous potential in the study of food biopolymers has yet to be reached. The aim of this paper is principally to provide information on biopolymers using Fourier transform infrared spectroscopy. β-Lactoglobulin (β-Lg), the major whey protein in the milk of ruminants, is chosen as a model. Emphasis will be put on the different structure levels of proteins in an aqueous solution, the protein–protein interactions, and the protein interactions with small host-molecules such as phospholipids.