Macromolecular Matrix Research Articles

Gas phase hydrogenation reaction using a ‘metal nanoparticle–polymer’ composite catalyst

A facile synthesis route is described here for the preparation of a poly (anthranilic acid)-palladium nanoparticle composite material by polymerization of anthranilic acid (AA) monomer using palladium acetate (PA) as the oxidant. It was found that oxidative polymerization of AA leads to the formation of poly-AA (PAA), while the reduction of PA results in the formation of palladium nanoparticles with an average size of ~2 nm. The palladium nanoparticles were uniformly dispersed and highly stabilized within the macromolecular matrix resulting in a uniform metal–polymer composite material. The resultant composite material was characterized by means of different techniques, such as IR and Raman spectroscopy, which yielded information about the chemical structure of polymer, whereas electron microscopy images provided information concerning the morphology of the composite material and the distribution of the metal particles in the composite material. The composite material was tested as a catalyst for ethylene hydrogenation reaction and showed a catalytic activity at higher temperatures.

A mathematical model to predict the effect of shape on pasta hydration kinetic during cooking and overcooking

In this paper, a novel mathematical model to describe pasta hydration kinetic during cooking and overcooking is presented. The model takes into account the water diffusion process, the relaxation of the macromolecular matrix and the starch gelatinization process. The target pasta samples have three different geometries, specifically plane sheet, solid cylinder and hollow cylinder. The proposed model satisfactorily fits the experimental data, showing its ability to predict hydration kinetics for all the considered geometries. It is also successfully applied to predict the evolution of water concentration profiles.

Detection of Cortisol in Saliva with a Flow-Filtered, Portable Surface Plasmon Resonance Biosensor System

Saliva provides a useful and noninvasive alternative to blood for many biomedical diagnostic assays. The level of the hormone cortisol in blood and saliva is related to the level of stress. We present here the development of a portable surface plasmon resonance (SPR) biosensor system for detection of cortisol in saliva. Cortisol-specific monoclonal antibodies were used to develop a competition assay with a six-channel portable SPR biosensor designed in our laboratory. The detection limit of cortisol in laboratory buffers was 0.36 ng/mL (1.0 nM). An in-line filter based on diffusion through a hollow fiber hydrophilic membrane served to separate small molecules from the complex macromolecular matrix of saliva prior to introduction to the sensor surface. The filtering flow cell provided in-line separation of small molecules from salivary mucins and other large molecules with only a 29% reduction of signal compared with direct flow of the same concentration of analyte over the sensor surface. A standard curve for detection of cortisol in saliva was generated with a detection limit of 1.0 ng/mL (3.6 nM), sufficiently sensitive for clinical use. The system will also be useful for a wide range of applications where small molecular weight analytes are found in complex matrixes.

Macromolecular Salen Catalyst with Largely Enhanced Catalytic Activity

A dinuclear copper(II) Schiff-base complex was immobilized in a poly(acrylate) matrix by emulsion polymerization. The spheric microbeads were used for aerobic catalytic oxidation of 3,5-di-tert-butylcatechol into 3,5-di-tert-butylquinone in methanol at ambient temperature to study the contribution of the macromolecular matrix to the overall rate acceleration of the reaction. The polymeric catalyst catalyzes the oxidation about 1 order of magnitude faster (kcat/knon = 470,000) than its low molecular weight analogue (kcat/knon = 60,000).

Template Adaptability Is Key in the Oriented Crystallization of CaCO3

In CaCO3, biomineralization nucleation and growth of the crystals are related to the presence of carboxylate-rich proteins within a macromolecular matrix, often with organized beta-sheet domains. To understand the interplay between the organic template and the mineral crystal it is important to explicitly address the issue of structural adaptation of the template during mineralization. To this end we have developed a series of self-organizing surfactants (1-4) consisting of a dodecyl chain connected via a bisureido-heptylene unit to an amino acid head group. In Langmuir monolayers the spacing of these molecules in one direction is predetermined by the hydrogen-bonding distances between the bis-urea units. In the other direction, the intermolecular distance is determined by steric interactions introduced by the side groups (-R) of the amino acid moiety. Thus, by the choice of the amino acid we can systematically alter the density of the surfactant molecules in a monolayer and their ability to respond to the presence of calcium ions. The monolayer films are characterized by surface pressure-surface area (pi-A) isotherms, Brewster angle microscopy, in-situ synchrotron X-ray scattering at fixed surface area, and also infrared reflection absorption spectroscopy (IRRAS) of films transferred to solid substrates. The developing crystals are studied with scanning and transmission electron microscopy (SEM, TEM), selected area electron diffraction (SAED), and crystal modeling. The results demonstrate that although all compounds are active in the nucleation of calcium carbonate, habit modification is only observed when the size of the side group allows the molecules to rearrange and adapt their organization in response to the mineral phase.

Relaxation of protons by radicals in rotationally immobilized proteins

Proton spin–lattice relaxation by paramagnetic centers may be dramatically enhanced if the paramagnetic center is rotationally immobilized in the magnetic field. The details of the relaxation mechanism are different from those appropriate to solutions of paramagnetic relaxation agents. We report here large enhancements in the proton spin–lattice relaxation rate constants associated with organic radicals when the radical system is rigidly connected with a rotationally immobilized macromolecular matrix such as a dry protein or a cross-linked protein gel. The paramagnetic contribution to the protein–proton population is direct and distributed internally among the protein protons by efficient spin diffusion. In the case of a cross-linked-protein gel, the paramagnetic effects are carried to the water spins indirectly by chemical exchange mechanisms involving water molecule exchange with rare long-lived water molecule binding sites on the immobilized protein and proton exchange. The dramatic increase in the efficiency of spin relaxation by organic radicals compared with metal systems at low magnetic field strengths results because the electron relaxation time of the radical is orders of magnitude larger than that for metal systems. This gain in relaxation efficiency provides completely new opportunities for the design of spin–lattice relaxation based contrast agents in magnetic imaging and also provides new ways to examine intramolecular protein dynamics.

Computational polymer dynamics via DL_POLY

A review is presented of recent work in the group utilising the DL_POLY molecular dynamics package. Simulations have been performed across several areas of polymer physics including the dynamics of polyethylene as a function of density and chain length, the rheology of trifunctional dendrimers, and penetrant diffusion with a macromolecular matrix. The methodology and conclusions of these investigations are reviewed.

Poly( N-vinylpyrrolidone)-hydrotribromide: A new gel-type resin for alcohol oxidation and alkene dibromination

Poly( N-vinylpyrrolidone) crosslinked with tetraethyleneglycol diacrylate was prepared and used as solid support for immobilizing bromine function. The resin bound hydrotribromide was found to be an efficient reagent for the oxidation of alcohols and dibromination of alkenes. The role of the macromolecular matrix in dictating the efficiency of the oxidizing reagent was elucidated by preparing crosslinked polyvinylpyrrolidone resins with varying mole percent of cross-linking agent. Studies revealed that the extent of functionalisation as well as the reactivity of the oxidizing function was highly dependent on the degree of crosslinking of the macromolecular matrix. The effect of various reaction conditions such as the temperature, solvent and molar concentration of the reagent was also examined in order to find the optimum conditions for oxidising reactions.

Studies on Some Metal Complexes of a Pyrazole Functionalized Crosslinked Polystyrene Resin

Pyrazole functionalized cross-linked polystyrene resins with three carbon spacer groups between backbone and functionality were prepared. Complexation studies with transition metal ions such as Fe(III), Co(II), Ni(II) and Cu(II) reveal effective coordination of the pyrazole functionalized ligands. The structural factors of the macromolecular matrix, like the nature and extent of crosslinking hydrophilic/hydrophobic balance and the spacer between the ligand function and the polymer matrix, are shown to be important in the complexation behavior of polymeric ligands. Experimental conditions such as the pH, time and temperature also affect the chelating capacity of the polymeric ligand. The complex formation was confirmed using IR; stereochemical studies were done by UV and ESR; resin morphology was studied using SEM; and the thermal stability of the complexes was studied using thermogravimetry.

Immobilization of catalase on a novel polymer support, crosslinked polystyrene ethylene glycol acrylate resin: Role of the macromolecular matrix on enzyme activity

AbstractCrosslinked polystyrene ethylene glycol acrylate resin (CLPSER) was developed for the immobilization of the enzyme catalase by the introduction of a crosslinker, O,O′‐bis(2‐acrylamidopropyl) poly(ethylene glycol)1900, to styrene. The crosslinker was prepared by the treatment of acryloyl chloride with O,O′‐bis(2‐aminopropyl) poly(ethylene glycol)1900 in the presence of diisopropylethylamine. The resin was characterized with IR and 13C‐NMR spectroscopy. The catalytic activity of the catalase‐immobilized system of CLPSER was compared with divinylbenzene‐crosslinked polystyrene, ethylene glycol dimethacrylate crosslinked polystyrene, and 1,4‐butanediol dimethacrylate crosslinked polystyrene systems. Crosslink levels of 2, 8, and 20 mol % were evaluated. Among these crosslinked systems, the 2 mol % system was found to be most suitable to support catalytic activity. When a long flexible hydrophilic poly(ethylene glycol) crosslink, introduced between the polystyrene (PS) backbone and functional groups was used for immobilization, the extent of coupling and enzyme activity increased. Depending on the nature of the support, the catalytic activity of the system varied. The hydrophilic CLPSER support was most efficient for immobilization compared to the other PS‐based supports. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 8–19, 2005

Influence of protein content on spaghetti cooking quality

Water sorption tests on three different types of laboratory-made spaghettis were conducted at 100 °C to study the influence of protein content on hydration kinetics during cooking and overcooking and on quality characteristics. In particular, the weight, diameter and length of spaghetti strands were monitored over a 20 min period. The different hydration behaviours of the spaghettis were analyzed using a mathematical model that quantitatively resolved the hydration process into the controlling factors (i.e. water diffusion, macromolecular matrix relaxation kinetics, and ‘residual deformation’ release kinetics). Only small differences were observed within the range of protein contents (12.7–15.5%) investigated. In particular, spaghetti stickiness decreased as protein content increased. Moreover, samples with intermediate protein contents showed the highest water diffusion coefficients.

Evaluation of the water sorption and controlled‐release potential of binary polymeric beads of starch and alginate loaded with potassium nitrate as an agrochemical

AbstractBinary polymeric beads of sodium alginate and starch were prepared and characterized by IR spectral and scanning electron microscopy (SEM) techniques. The beads were examined for water uptake potential, and he influence of various factors, including chemical composition of the macromolecular matrix, pH, ionic strength, and temperature of the swelling medium, were investigated on the degree of water sorption. The prepared beads were loaded with KNO3, as a model agrochemical, and the release kinetics of KNO3 were studied under varying experimental conditions, as mentioned previously. The release data were analyzed by Fick's equation, and the mechanism of KNO3 release was worked out at different experimental conditions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1815–1826, 2004

High-Temperature-Tolerant, Proton-Conducting Polytetramethylene Oxide/Zirconia Hybrid Membranes

Nanohybrid membrane of zirconia/polytetramethylene oxide synthesized by sol-gel processes was shown to possess flexible and temperature-tolerant properties. The polymeric membrane showed enhanced thermal stability up to 300°C due to the presence of cross-linkable inorganic nanophase in the hybrid macromolecular matrix. The membrane becomes proton-conducting polymer electrolyte when added with 12-phosphotungstic acid (PWA) or soaked by phosphoric acid. The proton-conducting properties of the hybrid membranes with various PWA or phosphoric acid concentrations were investigated in the temperature range from room temperature to 150°C under saturated humidity conditions. The flexible and large-sized hybrid polymer membrane has been found to have high proton conductivities from to under saturated humidity condition between 100 and 150°C. © 2004 The Electrochemical Society. All rights reserved.

NMR investigations of the 4-ethyl guaicol self-diffusion in iota (ι)-carrageenan gels

Self-diffusion coefficient of an aroma molecule (4-ethyl guaicol) was measured using the pulsed field gradient spin echo NMR (PGSE-NMR) method in order to investigate the influence of a macromolecular matrix on its diffusion and release processes. Iota (ι)-carrageenan was used for its ability to form thermoreversible gels in aqueous salt solutions. Variations of the ι-carrageenan and the salt concentrations permitted various gels with different thermal and rheological properties to be obtained. These latter were modified by an isotope effect obtained by preparing gels in D 2O. The NMR self-diffusion measurements realised for water and the aroma molecules indicated neither chemical interactions with ι-carrageenan, nor obstruction effects from the polysaccharide chains. In ι-carrageenan gels, the diffusional phenomenon was highly dependent on the heterogeneous gel structure and controlled by hydrodynamic interactions due to frictional drag between each molecule of the system and water microviscosity changes.

Proton conducting polydimethylsiloxane/metal oxide hybrid membranes added with phosphotungstic acid(II)

Flexible polymer electrolyte membranes consisting of zirconia (titania) and polydimethylsiloxane (PDMS) with the different molecular mass of 4500 and 600 have been synthesized by sol–gel processes. The polymeric membranes showed thermal stability and flexibility up to 300 °C due to the presence of cross-linkable inorganic nano-phase in the hybrid macromolecular matrix. The membrane becomes proton conducting polymer electrolyte by addition of 12-phosphotungstic acid (PWA). The conductivity increased up to 7.7×10 −2 S/cm through ultrasonic treatment on the membrane, which is in the application level to polymer electrolyte fuel cells. The hybrid materials can be recognized as new, low cost and environment friendly electrolyte membranes.

Contribution of dead-space microdomains to tortuosity of brain extracellular space

The extracellular space (ECS) of the brain is a major channel for intercellular communication, nutrient and metabolite trafficking, and drug delivery. The dominant transport mechanism is diffusion, which is governed by two structural parameters, tortuosity and volume fraction. Tortuosity ( λ) represents the hindrance imposed on the diffusing molecules by the tissue in comparison with an obstacle-free medium, while volume fraction ( α) is the proportion of tissue volume occupied by the ECS. Diffusion of small ECS markers can be exploited to measure λ and α. In healthy brain tissue, λ is about 1.6 but increases to 1.9–2.0 in pathologies that involve cellular swelling. Previously it was thought that λ could be explained by the circumnavigation of diffusing molecules around cells. Numerical models of assemblies of convex cells, however, give an upper limit of about 1.23 for λ. Therefore, additional factors must be responsible for λ in brain. In principle, two mechanisms could account for the measured value: a more complex ECS geometry or an extracellular macromolecular matrix. Here we review recent work in ischemic tissue suggesting concave geometrical formations, dead-space microdomains, as a major determinant of extracellular tortuosity. A theoretical model of λ based on diffusion dwell times supports this hypothesis and predicts that, in ischemia, dead spaces occupy ≈60% of ECS volume fraction leaving only ≈40% for well-connected channels. It is further proposed that dead spaces are present in healthy brain tissue where they constitute about 40% of α. The presence of dead-space microdomains in the ECS implies microscopic heterogeneity of extracellular channels with fundamental implications for molecular transport in brain.

Influence of Raw Materials and Processing Conditions on Spaghetti Hydration Kinetic During Cooking and Overcooking

ABSTRACTA study of the influence of raw materials and processing conditions on the hydration kinetic during cooking and overcooking of spaghetti is presented. Water sorption tests on commercially available spaghetti and on three different types of homemade spaghetti were run at 100°C. In particular, the weight, diameter, and length of spaghetti strands were monitored over time for ≈200 min. The spaghetti hydration process was quantitatively resolved into the controlling phenomena (i.e., water diffusion, macromolecular matrix relaxation kinetic, and residual deformation release kinetic) by fitting a novel mathematical model to the experimental data. The different behavior of spaghetti was analyzed for each of the phenomena involved during hydration. Results suggest that processing conditions highly influence the quality of spaghetti with respect to raw materials.

Swelling controlled delivery of antibiotic from a hydrophilic macromolecular matrix with hydrophobic moieties

A hydrophilic macromolecular network containing hydrophobic moieties has been prepared by free radical copolymerization of acrylamide and styrene in the presence of poly(vinyl alcohol) (PVA) and its potential as controlled drug delivery carrier was evaluated with tetracycline as a model antibiotic drug. The amount of drug was assayed spectrophotometrically. The network was characterized by optical microscopy, infra-red spectroscopy and structural parameters such as average molecular weight between crosslinks (M c ), crosslink density (q) and number of elastically effective chains (V e ) were evaluated. It was found that with increasing concentration of PVA, ST and MBA in the hydrogel, the release rate initially increases but after definite concentrations of the above components the release rate falls. In the case of AM, release rate constantly decreases with increasing AM concentration in the hydrogel.

Modeling the Spaghetti Hydration Kinetics During Cooking and Overcooking

ABSTRACT: A mathematical model to predict the hydration kinetics of spaghetti during cooking and overcooking is presented. The phenomena involved during the hydration process, such as starch crystalline domains melting kinetics, water diffusion, macromolecular matrix relaxation kinetics, and “residual deformation” release kinetics, were separately described. To validate the developed model, water sorption tests on commercially available spaghetti strands were run at 100 °C. In particular, the weight, diameter, and length of spaghetti strands were monitored over a period of 200 min. The fitting and predictive ability of the model was successfully tested, corroborating the validity of the approach used to derive the model.

DDT-related compounds bound to the nonextractable particulate matter in sediments of the Teltow Canal, Germany.

Sediment samples of the Teltow Canal (Berlin, Germany) were analyzed with respect to extractable and nonextractable organic compounds. The study focused on the identification and quantitation of bound 2,2-bis(chlorophenyl)-1,1,1-trichlorethane (DDT) residues in order to obtain further information about the fate of DDT-derived compounds within the particulate matter of the aquatic environment. Various chemical degradation techniques and a complementary online pyrolysis-GC/MS method were applied to the pre-extracted sediment residues. Generally, the distribution of the bound DDT-related compounds was found to differ distinctly from the substances distribution within the extractable fraction. The main metabolite of the anaerobic degradation pathway (2,2-bis(chlorophenyl)-1,1-dichlorethane, DDD) is most abundant in the sediment extracts but occurred only in insignificant concentrations in the degradation products of all procedures applied. The most abundant DDT-metabolites released after the degradation procedures were 4,4'-DBP, 4,4'-DDA, and 4,4'-DDM. In addition, 4,4'-DDM was detected at rather high concentrations by pyrolytic analysis. The results imply a weak association to the nonextractable particulate matter based on noncovalent interactions for the observed DDT-related contaminants. The release of these compounds was initiated by the modification and degradation of the organic macromolecular matrix as well as of the inorganic material. Furthermore, numerous methoxychlor-related compounds were detected not only in the extracts but also in parts of the hydrolysis products.