bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrooxidation of aromatics to polymer films
Authors: LaCroix Jean‐Christophe , Diaz A. F.
Published: March 2011

This report describes the electrochemical preparation and properties of polyaniline films prepared on a bare platinum electrode and on electrodes precoated with a thin film of inert polymer. Films were prepared and studied in several aqueous acid electrolytes including sulfuric, hydrochloric, nitric, trifluoromethylsulfonic, hydrofluoric and trifluoroacetic acid. It is observed that both the concentration and nature of the acid influence the kinetics of the switching reaction. In the more acidic solutions, the reaction has at dependence and depends on the movement of a front across the thickness of the film. In the less acidic solutions, the reaction has a t1/2 dependence and depends on the diffusion of ions in the film. The same response is observed for the oxidation and the reduction reaction. Polyaniline is also electroactive in other various nonaqueous solvents, such as, alcohols, acetic acid and acetonitrile, and voltammograms with well defined waves result when solution contains both organic salt and protic acid. Polyaniline was also prepared on a platinum electrode coated with an inert polymer film such as polymethylmethacrylate (PMMA). The resulting polymer blend is electroactive and the switching reaction is slower than for polyaniline formed on a bare platinum electrode. Finally, a brief description is given of electroactive polyaniline films which can be prepared by polymerization of aniline in a glow discharge.
In‐situ IR spectra of polypyrrole layers on gold electrodes
Authors: Daroux M. L. , Yeager E. B. , Kalaji M. , Cuong N‐H , Bewick A.
Published: March 2011

Electrochemically modulated infrared spectroscopy (EMIRS) has been used to study the changes occurring in polypyrrole films during electrochemical oxidation and reduction. Films containing perchlorate, tetrafluoroborate and ferrocyanide counterions have been studied in both aqueous and nonaqueous electrolytes. With the EMIRS technique it has been possible to detect electrochemically produced changes in the polymer backbone, in the counterion species and in incorporated solvent.
The ionic mechanism of the electrochemical doping of poly (3–methylthiophene) studied by secondary ion mass spectroscopy (SIMS)
Authors: Chao F. , Baudoin J. L. , Costa M. , Lang P.
Published: March 2011

The concentration profiles of C104− and Li+ into the poly(3‐methylthiophene) structure were referred to the 3‐methylthiophene concentration for several doping levels during the doping and the undoping processes. The ion amount is very different in the polymer bulk and in a surface region of about 150 Å thickness. The cation is shown to play a role in the first step of the undoping mechanism. The paired ions concentration was determined and an actual doping ratio could be deduced which is different from that calculated by coulometry.
Preparation of polymer phthalocyanine electrodes and their electrochemical properties
Authors: Wührle Dieter , Schumann Bernd , Schmidt Volker , Jaeger Nils
Published: March 2011

Phthalocyanine coated electrodes are of interest due to their high electrochemical and electrocatalytical activities. Several possibilities to prepare electrodes coated by polymeric phthalocyanine and its precursor are described. Examples of electrochemical (reduction/reoxidation of the films) as well as electrocatalytical properties are presented.
Electrocatalytic aspects of electrogenerated polymer layers
Authors: Barendrecht E. , Elzing A. , Janssen L. J. J. , van der Putten A. , Visscher W. , Vork F.
Published: March 2011

Two main aspects of electrocatalysis of electrogenerated polymer layers (polypyrrole in this case) are presented here. The first aspect concerns the electrogenerated conducting polypyrrole layer as such; i.e. its preparation with built‐in electrocatalysts, like Pt or metal‐organic complexes. Its properties are discussed in terms of their real electrocatalytic behaviour, viz. their turn‐over numbers. The second part deals with specific studies like:

‐ the anodic oxidation of hydrogen with built‐in Pt, and,

‐ the cathodic reduction of oxygen with Co and/or Fe‐phthalocyanines.

The theoretical model predicts rather well the experimental behaviour.
Poly(phenylene oxide); electropolymerization on mild steel and anticorrosive properties of the layer: A new corrosion test
Authors: Otero T. F. , Ponce M. T. , Jiménez Y. J.
Published: March 2011

The electropolymerization of phenyl salicylate by cyclic potential sweeps over mild steel gives rise to the formation of a poly(phenylene oxide) (PPO) film. In order to study the anticorrosive properties of PPO a new rapid corrosion test has been devised.
Electrocoagulation of waterborne polymers in the presence of carbon black
Authors: Beck Fritz , Guder Harald
Published: March 2011

Electrodeposition of paint is an electrochemical process, starting from water‐borne polymers. The electrode reactions are water decomposition, leading to diffusion layers of an extreme pH. Coagulation of polymers proceeds in these layers as an acid / base reaction rather than as a direct discharge of macroions at the electrodes. The electrodeposited film behaves like a weak acid or alkaline ion exchanger. Under polarization, high electric field strength leads to charge separation and the formation of a double space charge. Current / voltage‐behavior is nonlinear. The mechanism of charge transport is purely ionic. Resistivities are in the order of p = 108 Ohm·cm in the wet film. The stoved film is an insulator. Electrodeposition of a second film is impossible. However, electrodeposition of the primary film in the presence of dispersed carbon black, studied in detail for the first time, leads to an appreciable electronic conductivity in the stoved film. ρ is in the order of 105 ‐ 107 Ohm·cm even with a carbon black concentration of only a few wt.‐%. This has been explained in terms of a stick percolation model and the preferential formation of transversal carbon black chains in the film. The relatively high resistivities found along these chains is due to the need of electron tunneling through ultrathin polymer films around the polymer wetted individual carbon black particles. Temperature behavior of resistivities, field effect and other proofs are given for this model.

For practical application, the most important findung is the possibility of an electrodeposition of a coherent second layer and even of multilayers in the presence of only 1 ‐ 5 wt.‐% of an appropriate carbon black filler.
Preparation and electrochemical behaviour of electrodes coated with glow‐discharge–polymer films
Authors: Doblhofer Karl
Published: March 2011

The electrical parameters of low‐pressure glow‐discharges are discussed with respect to formation of high‐quality organic thin films on conducting substrates. It is demonstrated theoretically and experimentally that ac discharges operated at frequencies of the order of 10 KHz are well suited for producing flawless dielectric films.
The produced coatings are characterized by electrochemical methods and by electron microscopy. The permeability of the film, its relationship with the chemical nature, and the associated electrochemical behaviour are discussed.
Electropolymerization and conductivity of inhibitors with 2–(5–aminopentyl) benzimidazole
Authors: Schultze J. W. , Rolle D.
Published: March 2011

Polymer layers of inhibitors are supposed to be electronically and ionically insulating. Potentiostatic investigations of film growth with PAB demonstrated a self‐inhibiting process which is explained by the limiting electron conductivity of the polymer. Correspondingly, the electrode capacity C decreases with film thickness d, but the potential drop extends over a thin inner film only with an effective thickness deff << d. These results are consistent with the decrease of the current density i of electron transfer reactions. The long‐time behaviour of the films is more complex since ions can slowly diffuse into the film. Small ions, like protons, and molecules, like water, can rapidly move through the film. Hence, oxide formation can take place at the metal/PPAB interface. Conductivity data are estimated.
Electrochemical and spectroscopic characterisation of structural reorganisation in N, N′–dialkylpyridinium cation radical deposits
Authors: Bewick A. , Cunningham D. W. , Lowe A. C.
Published: March 2011

The electrochemical reduction to form a deposit of the radical cation salt for a series of n‐alkyl asymmetrically substituted viologens and the corresponding anodic oxidation processes have been investigated using electrochemical methods in in situ uv‐visible reflectance spectroscopy. Particular attention was focussed on the nature of the restructuring involved in the ageing of the deposit. The use of both p‐ and s‐polarised radiation clearly showed that initially the viologen units were deposited with the major molecular axis parallel to the electrode and on ageing they reorganised into a preferred orientation perpendicular to the electrode. The viologens with the larger substituents were initially deposited as aggregates of mixed micelles containing both cation radical and dication units. The latter were reduced at a well defined potential, the process being seen as a highly‐reversible sharp current spike on the linear sweep voltammograms.
Synthetic polymers in biology and medicine
Authors: Scheler W.
Published: March 2011

Synthetic organic polymers have gained great importance as supports and separation materials in biochemical laboratory techniques, medical diagnostics and biotechnological procedures. Furthermore they are used as carriers for drugs and biologically active substances in pharmacy, medicine and agriculture. Classifying their biocompatibility it has to be distinguished between in vitro application of polymers interacting on the one hand with molecular biosystems such as proteins and on the other hand with living cells, and in vivo administration in higher organisms, especially in the human organism.
Multiplicity of active species in transition metal based catalysts: The various reaction processes involved
Authors: Sigwalt P. , Deffieux A.
Published: March 2011

Products resulting from the polymerization of α‐olefins and of styrene initiated by transition metal based catalytic systems may range from dimers of various structures to high mol. wt. polymers of different stereoregularities. In this report, it is shown that such a large variety of products may be obtained using the same transition metal compound.

Initiating systems derived from tetrabenzylzirconium are first examined. The nature of the various mechanisms involved according to polymerization conditions are discussed. A rather similar situation is observed for systems derived from titanium trichloride. In this series, however, Ziegler‐type processes can be generated much more cleanly. This led us to examine the mechanisms in more detail in order to distinguish the various types of active species which may participate to these polymerizations.
On the reactivity of supported zirconium organic catalysts in the polymerization of ethylene
Authors: Ulbricht Joachim , Giesemann Jürgen
Published: March 2011

The ethylene polymerization with tetrabenzyl zirconium displays a higher concentration of active centres on catalysts obtained by supporting of the organometallic compound on alumina or silica‐alumina carriers than by activation without supporting. The active centres of the supported catalysts possess different polymerization reactivity. At the beginning of the polymerization in the presence of monomer, these active centres are formed from a small amount of the stable surface compounds originated in the carrier impregnation. The maximum polymerization rate depends on the pretreatment, the loading and the porosity of the carrier. The more active these centres, the quicker they lose their activity. A relation was found between a chemical deactivation reaction and the concentration of the hydroxyl groups remaining on the catalyst after impregnation. Addition of hydrogen or butyllithium can change the polymerization in a different manner. The addition of butyllithium causes an increase in the number and the reactivity of the active centres and a suppression of the chemical deactivation.
Prediction of phase equilibrium behavior of quasibinary polymer solutions
Authors: Fujita Hiroshi , Einaga Yoshiyuki
Published: March 2011

A chronological review is given of typical contributions which played a role in approaching quantitative predictions of phase equilibria in binary and quasibinary polymer solutions. It describes step by step findings of the variables which govern phase separations in these systems. These variables are temperature, overall polymer concentration, and chain length distribution of the polymer mixture making up the solution. The last variable gives rise to a considerable difficulty in formulating the free energy of quasibinary solutions.
Polydispersity treated by continuous thermodynamics
Authors: Rätzsch Margit T.
Published: March 2011

Continuous thermodynamics is a suitable concept for performing phase equilibrium calculations of polydisperse systems such as polymer solutions or polymer mixtures. In contrast to the traditional pseudo‐component method the continuous molar mass distribution density function obtained by fractionation or gel permeation chromatography is used directly for thermodynamic calculations. This paper describes the application of continuous thermodynamics to calculate cloud‐point curves, shadow curves and coexistence curves for solutions and mixtures of homopolymers and random copolymers. Particular attention is devoted to special problems such as fractionation or the transition from polymers to oligomers requiring the application of sophisticated Gibbs energy functions. In all cases the use of continuous thermodynamics leads to a drastic reduction of the required computer time. For Schulz‐Flory distributions the occurring integrals often may be calculated analytically leading to simple closed end formulas.
Changes in lignin and cellulose by irradiation
Authors: Fischer Klaus
Published: March 2011

The effect of high‐energy radiation on wood and cellulose was investigated. By irradiation of beech wood, changes in lignin, in carbohydrates and in wood structure take place. Furthermore, new lignin carbohydrate complexes are formed. A way is shown to prevent undesirable reactions. Irradiated pulp possesses a lower degree of polymerization and a higher accessibility for chemical reactions. Processing irradiated pulp to viscose fibres will be more efficient.
Biomedical behavior of some amino‐containing polymers in contact with blood constituents
Authors: Tsuruta Teiji
Published: March 2011

The present paper is concerned with studies for elucidation of the relationship between the structure of HA copolymers and their adsorption property toward lymphocyte subpopulations, B cell and T cell. HA is a polyamine graft copolymer of poly(hydroxyethyl methacrylate) as the backbone. In the earlier part of this paper, discussion will be made on our synthetic approach to HA copolymers having polyamine graft chains of controlled length and number, while, in the later part, the outline of our recent studies of biomedical behavior of HA copolymers in terms of selective adsorption of B cell against T cell will be presented. A possible mechanism for the cell separation will also be discussed.
Polymer modification to achieve novel properties
Authors: Vogl Otto , Sustic Andres
Published: March 2011

Polymers have been modified, by subjecting them to reactions in solution, in the melt and in the solid state. Novel polymers with improved and optimized properties have also been created by copolymerization, chain transfer or by the design of chain termination. Even by manipulating the initiation step in polymerizations, functional and reactive groups have been introduced at the head of the polymer chain. Polymer properties have been modified by influencing physical properties of polymers by orienting, annealing and blending.
X‐ray crystallography at macromolecular resolution: A solution of the phase problem
Authors: Luzzati V. , Mariani P. , Delacroix H.
Published: March 2011

The problem of crystal structure analysis at macromolecular resolution is tackled using notions borrowed from small‐angle solution‐scattering studies. The mathematical procedure ‐ essentially a pattern recognition approach ‐ consists of generating all the phase combinations compatible with the data and screening them: the critical steps are the choice of the “pattern” and of the criteria which preside the “recognition”. Two strategies are adopted. One is based upon use of the histogram of the electron density maps, a function more dependent on chemical composition than on physical structure: the histograms of samples of different structure and similar chemical composition are compared in search for similarity. The other strategy operates on the electron density maps and involves the principle of maximum smoothness. From the practical viewpoint, one single parameter, (Δp)4, is found to play an outstanding role in the two cases. Algorithms are worked out, implemented on the computer and tested using a variety of lipid‐water phases. The comparison of samples of different structure and similar chemical composition is found to provide a powerful screening criterion. The principle of maximum smoothness is also of great help, at least to the extent that the electron density distribution is a fairly smooth function, devoid of sharp peaks (associated with heavy atoms). The practical aspects of the algorithms are discussed, as well as their possible application to crystallographic problems of more general interest.
Time‐of‐flight small‐angle scattering spectrometers on pulsed neutron sources
Authors: Ostanevich Yurii M.
Published: March 2011

The operation principles, constructions, advantages and shortcomings of the known Time‐of‐Flight Small‐Angle Neutron Scattering (TOF SANS) spectrometers built up on pulsed neutron sources are reviewed. The most important characteristics of TOF SANS apparatuses are rather a high luminosity and the possibility of measurement in an extremely wide range of the scattering vector at a single exposure. This is achieved by simultaneous employment of the white beam, TOF technique for Λ‐scan and the commonly known θ‐scan. However, the electronic equipment, data‐matching programs and the measurement procedure, necessary for accurate normalization of experimental data and their transformation into absolute cross‐section scale ‐ they all become more complex as compared with those for SANS apparatuses operating on steady‐state neutron sources, where only θ ‐scan is used.
A complete mapping of the positions of the proteins in the small ribosomal subunit of escherichia coli
Authors: Capel M.S. , Engelman D.M. , Freeborn B.R. , Kjeldgaard M. , Langer J.A. , Ramakrishnan V. , Schindler D.G. , Schneider D.K. , Schoenborn B.P. , Sillers I.‐Y. , Yabuki S. , Moore P.B.
Published: March 2011

The relative positions of the centers of mass of the 21 proteins of the 30S ribosomal subunit from Escherichia coli have been determined by triangulation using neutron scattering measurements in solution. This mapping is the first complete account of the quaternary structure of the small ribosomal subunit to be obtained by any method.
Small‐angle scattering in materials science
Authors: Kostorz Gernot
Published: March 2011

The use of small‐angle scattering techniques in the study of inhomogeneities and microstructural changes in inorganic materials is reviewed with emphasis on X‐ray scattering. Recent applications of anomalous scattering with synchrotron radiation and kinetic studies in amorphous and crystalline systems are stressed.
Small‐angle X‐ray scattering of catalysts: Recent research
Authors: Brumberger H.
Published: March 2011

Recent investigations of appropriate models, and experimental applications of small‐angle X‐ray scattering (SAXS) to heterogeneous catalysts are reviewed. Some new work on mixed‐oxide and carbon‐supported catalysts is briefly discussed.
Small‐angle scattering from dense systems of non‐homogeneous particles, I
Authors: Syneček Vladimír
Published: March 2011

The introduction of the effective integral quantities characterizing non‐homogeneous particles and their volume fraction leads to an expression for the distance distribution function analogous to that for homogeneous particles. This significantly simplifies the determination of the structure characteristics of particles. The procedure is outlined for obtaining the distribution of excess electrons and the total number of electrons within the particle from relative SAXSb) intensity data. The mode of the spatial arrangement of the partially ordered system of particles can be estimated by comparing the characteristic numbers calculated for different structure types with that characteristic number determined from relative intensities, namely from the effective quantities of the system and from the position of the maximum of interference function.
Determination of compositions of Guinier‐Preston zones and matrix in Al‐Zn alloys using relative intensities, II
Authors: Truong Chu Thien. , Syneček V. , Wendrock G. , Löffler H.
Published: March 2011

The composition of Guinier‐Preston (GP) zones (cZ) and matrix (cM) in an Al‐15 mol‐% Zn alloy was determined for temperatures ranging between 80 and 180°C by applying a new method. The volume fraction of the GP zones is evaluated by their mean size and spacing. The latter quantity is computed from the position of the maximum of the interparticle interference function.
Analysis of small angle neutron scattering data from strongly interacting polydisperse ionic micellar solutions
Authors: Chen Sow‐Hsin , Sheu Eric Y.
Published: March 2011

Small angle neutron scattering (SANS) intensity distributions from ionic micellar solutions without added salt generally show a prominent interaction peak at finite Q (magnitude of the wave vector transfer) related to a certain inter‐micellar correlation distance. Analysis of this type of data requires, aside from the structural model of the micelle itself, a statistical mechanical theory for dealing with the inter‐micellar correlations. We present a method for a consistent analysis of SANS data taking into account the surfactant chain packing, the aggregation number polydispersity, and the effective micellar charge. The micelle is modelled as a two‐region spheroidal particle and the inter‐micellar correlations calculated according to a generalized one‐component macroion (GOCM) theory. GOCM uses an effective inter‐micellar pair potential which is a finite concentration extension of the well‐known Derjaguin‐Landau‐Verway‐Overbeek (DLVO) double layer interaction potential. Two micellar solutions are treated as examples, namely that of sodium dodecyl sulfate (SDS) and sodium 1,2‐bis(2‐ethylhexyloxycarbonyl)ethanesulfonate (AOT). The effects of polydispersity are appreciable immediately above the critical micellar concentrations (CMC). Both the structural parameters of the micelle and the free energies of micellization and micellar growth can be extracted from SANS data.
Neutron scattering studies of the structure and assembly of spherical viruses
Authors: Timmins Peter A.
Published: March 2011

Studies of the structure of spherical viruses, using both classical solution scattering techniques, and in favourable cases, the technique of low‐resolution neutron crystallography, are described. Solution scattering studies, which began with the determination of the radial distribution of the various viral components, have evolved to the stage where it is now possible to follow the in vitro reassembly of virus particles. The limitations of spherical averaging present in solution scattering can in certain cases be overcome by the application of the contrast variation method to single crystals of a virus. Application of this technique to the structure of tomato bushy stunt virus (TBSV) is described.
Polymer blends ‐ current state of progress and future developments from an industrial viewpoint
Authors: Rudolph Hans
Published: March 2011

Technical and economic considerations have given polymer blends a major share in the increasing sales of plastics. This applies both to general‐purpose and to the higher value‐added materials. Thus it is scarcely surprising that almost all polymer manufacturers have now developed comprehensive ranges of blends having particular property profiles. The principal types of blends currently available are described.

The variety of products already developed should not be allowed to obscure the fact that certain conceivable and highly attractive property combinations have not so far been realized. If progress is to be made in this area, interdisciplinary cooperation between chemists and physicists in the fields of polymer chemistry, polymer physics and materials science is essential.
Miscibility enhancement in polymers via ionic interactions: Dynamic mechanical and NMR studies
Authors: Natansohn Almeria , Murali Rajagopalan , Eisenberg Adi
Published: March 2011

The presence of ionic interactions can be used to control the degree of miscibility of otherwise immiscible polymer systems. This control, in turn, allows one to prepare blends with a very wide range of “tailor‐made” properties. Several examples are cited. In some of these, the interactions are based on proton transfer from a donor site on one polymer to an aceptor site on another leading to ion‐ion interactions. In others, the transfer of a metal cation from an ionomer to a polar polymer, as a result of ion‐dipole interactions, is involved. Systems studied to date include, among others, mixtures of polystyrene with poly(ethyl acrylate), polyisoprene, segmented poly urethanes, poly(ethyleneimine), and poly(ethylene oxide). The polyurethane blends with polystyrene are discussed in some detail, focussing especially on the mechanism of miscibility enhancement as determined by NMR. This technique has also been utilised to study the dynamics of the coil overlap process in solution as well as the proximity of the polymer coils to each other. Two particularly noteworthy applications involve mixtures of poly (tetrafluoroethylene) (PTFE) or of phenylated poly(phenylene oxide) with poly (ethyl acrylate), which are also discussed in some detail. Blends of this type may be of special interest in membrane applications.
On the compatibilization of polymer blends
Authors: Vilgis T. A. , Noolandi J.
Published: March 2011

By means of statistical thermodynamics we consider the effect of a diblock copolymer on the interface of a demixed homopolymer blend. In contrast to the usual case where the blocks are identical with the components of the homopolymers, we investigate the use of arbitrary blocks XY respective to the A‐B blend. As examples, we calculate interfacial properties such as the interfacial tension and the width of the interface as well as the concentration profiles of the blocks. We expect a strong compatibilization effect if the blocks are sufficiently long and have a preferential repulsive interaction with one of the two homopolymers.
Theory of crystallizable block copolymers
Authors: Whitmore Mark Douglas , Noolandi Jaan
Published: March 2011

We present an equilibrium theory of diblock copolymers in which one of the blocks is crystallizable and the other is amorphous. The material is assumed to order in a lamellar structure of alternating semi‐crystalline and amorphous layers with the chemical bonds which connect the copolymer blocks lying in the interfacial regions between the layers. The amorphous blocks are modelled as flexible chains, each with one end (the joint) anchored in an interface. Their contribution to the free energy is calculated via the self‐consistent solution of the modified diffusion equations. The crystalline regions are modelled as folded chains, also with one end in an interfacial region (bonded to the corresponding end of an amorphous block).

We find that the calculated amorphous block‐free energies can be expressed as a single universal function depending on the total degree of polymerization of the amorphous block, its stretching, and a parameter proportional to the thickness of the interface. We have fitted an analytical form to this function, which can be used for any amorphous block, and we have combined it with our model of the crystallizable block to obtain scaling laws describing the equilibrium morphology.
The application of fracture mechanics to the impact behaviour of rubber‐toughened polyamides
Authors: Sunderland P. , Kausch H. H. , Schmid W. Arber E.
Published: March 2011

Rubber‐modification of polyamide is a widely‐applied method of improving material resistance under high strain rate loading. The processing conditions used for preparing such two‐phase blends strongly influence their structure and thus their subsequent impact properties. In the present work the relationships between production parameters, phase structure and impact resistance have been studied, and the rǒle of the rubber phase in promoting energy absorption investigated. It has been found that improved impact resistance, defined as a combination of high resistance to crack initiation and to crack propagation, is achieved by decreasing the polyamide phase viscosity while increasing the extrusion and injection temperatures, the mixing shear rate and the rubber phase volume fraction; an EPR modifier offers superior performance to a polybutadiene modifier; the dominant mechanisms of energy‐absorption are shearing and void formation, there being no clear evidence of crazing; the J‐integral technique of plastic fracture mechanics can be applied to Charpy impact testing; TEM allied with image analysis techniques provides quantitative morphological information on polymer blends.
Reversible and irreversible denaturation of proteins in chromatographic systems
Authors: Wetlaufer D.B.
Published: March 2011

Protein denaturation in typical chromatographic mobile phases is examined from kinetic and equilibrium viewpoints, preliminary to consideration of the binding of proteins to stationary phases. Protein binding to a stationary phase may result in concomitant stabilization or destabilization. Experiments to clarify mechanisms and/or to lead to stabilization of proteins against denaturation are discussed. Among the work to be discussed are the ion exchange chromatography of α‐chymotrypsinogen and hen egg lysozyme with mobile phases containing urea; reverse phase HPLC of RNase A and serum albumin with conventional mobile phases; and hydrophobic interaction chromatography of enolase, carbonic anhydrase, lysozyme, RNase A, and bovine pancreatic trypsin inhibitor, mediated by the surfactant CHAPS.
Influence of pressure on protein conformation
Authors: Lüdemann H.‐D.
Published: March 2011

The pressure effects in aqueous solutions of biopolymers are presented. It is shown, that pressure in the range of 300 to 800 MPa leads for small monomeric proteins to irreversible denaturation. Larger oligomeric enzymes and structural proteins dissociate reversibly in the pressure range around 100 MPa. The sign of the volume effects of the various noncovalent interactions contributing to the observed reaction and activation volumes is discussed.
Forces and mechanisms in the adsorption of uncharged and ionizable macromolecules and of proteins
Authors: Fleer G.J. , Lyklema J.
Published: March 2011

The main energetic and entropic factors determining the adsorption behaviour of neutral polymers, polyelectrolytes, and proteins are discussed. The driving force is the segment adsorption energy, opposing forces are the loss of chain conformation entropy and the entropy of (de)mixing. Mutual interactions between the segments play an important role, especially if the macromolecules carry charged groups.

Several examples are given of the dependency of the adsorption of flexible macromolecules on the adsorption energy, the solvent quality, the salt concentration, and the surface charge. In the case of proteins, the internal coherency of the molecule largely determines the adsorption behaviour. For relatively flexible proteins like HPA, entropic contributions are important and sometimes dominant; the nature of the surface is less critical. For rigid proteins like RNAse, the adsorption is mainly energetically determined, depending largely on the electrostatic interaction between protein and surface.
Experimental characterization of adsorbed macromolecule layers at solid/liquid interfaces
Authors: Killmann Erwin
Published: March 2011

A survey will be given on the experimental methods to characterize the structure of adsorbed polymer layers at solid/liquid interfaces. Characterization parameters accessible by experimental methods are: adsorption isotherm mostly determined from the difference in the solution concentration; fraction of adhered segments, obtained from IR‐, NMR‐ ESR‐spectrometry and from microcalorimetry; layer thicknesses of different type from ellipsometry, diffusion, sedimentation, viscosimetry, electrophoresis, force‐distance measurements between contacting layers and from segment density profiles obtained by SANS; adsorption enthalpies from microcalorimetry and from displacer‐technique. Own experimental data of the adsorption of olystyrene, poly(ethylene oxide)s (PHD), poly(N‐vinyl‐2‐pyrrolidone), poly‐(butyl methacrylate)s, poly(vinyl alcohol)s as well as copolymers from ethylene oxide and propylene oxide on interfaces of colloidal silica‐ and latexparticles and partially on flat chromium‐, platinum‐and gold surfaces from organic and aqueous solutions and characteristic results from the literature will be compared and discussed in order to get insight into the conformation of the adsorbed macromolecules.
Dynamic behaviour of hydrosoluble polymers at a solid/liquid interface
Authors: Varoqui Raphael , Pefferkorn Emile
Published: March 2011

The behaviour of flexible hydrosoluble polymers of high molecular weight: polyacrylamide and two polyacids, poly(α, L‐glutamic acid) and a copolymer of maleic acid was investigated in the context of their dynamic behaviour at solid/liquid interfaces. The adsorption rate is related to the structure of the surface in terms of remaining interacting surface sites. The desorption rate was measured by carrying out adsorption with radioactive labelled polymers, followed by exchange with unlabelled polymers. The slow exchange rate observed suggests a metastable equilibrium state owing to strong multisegment adsorption in the potential well of the surface. However, the “diffuse” polymer layer formed by loops which extend in the aqueous phase within distances of several hundred Angstroms “responds” reversibly to a change in the solvent composition. The latter effect was found by recording the hydrodynamic permeability of pores covered by the adsorbed polymer; the permeability to fluid flow is very sensitive to the loop layer thickness.
Adsorption kinetics of protein mixtures. A tentative explanation of “the vroman effect”
Authors: Cuypers Peter A. , Willems George M. , Hemker H. Coenraad , Hermens Wim Th.
Published: March 2011

A model for protein adsorption kinetics is presented. This model includes diffusion limited adsorption, adsorption and desorption rate constants which are dependent on the surface concentration and an interaction term for the mutual influence of the adsorbed protein molecules. It is shown that, in first approximation, the values of the adsorption and desorption rate constants are exponential functions of the surface concentration. Assuming an adequate interaction term it is possible to show with this model for the adsorption kinetics of a mixture of proteins that the ratio of the adsorbed proteins is strongly dependent on the overall surface concentration even if the ratio of the bulk concentrations of these proteins is kept constant. Differences in interaction terms for the different proteins offer a possible explanation for the peculiar behaviour of plasma protein adsorption on a surface at different dilutions of the plasma, the so called “Vroman effect”.
Biospecific complex formation as a tool for oriented immobilization
Authors: Turková J. , Fusek M. , Štovičková J. , Králová Z.
Published: March 2011

The formation of biospecific complexes between the carbohydrate moieties localized on the surface of enzyme molecules and lectins (Hsiao and Royer, Ref.3) or between the appropriate antigenic portions of peptide chains and antibodies (Solomon et al., Ref. 18) permits oriented immobilization to be carried out which makes the catalytic site of the immobilized enzyme perfectly accessible. We have performed such oriented immobilization with carboxypeptidase Y which was attached to concanavalin A ‐ Spheron. On the basis of the results of biospecific affinity chromatography of a conjugate of catalase and dextran carried out by Marshall and Humphreys (Ref. 14) on concanavalin A ‐ Sepharose we prepared active conjugate of chymotrypsin with various dextrans for our investigation of immobilization of chymotrypsin through a bound polysaccharide.

The experiments carried out by Solomon et al. (Ref. 18) with the immobilization of carboxypeptidase A via a complex of the enzyme with a suitable monoclonal antibody against carboxypeptidase A showed that the immobilized enzyme had the kinetic properties of native carboxypeptidase A. was more stable and could be used several times. Anti‐chymotrypsin immunoglobulin G(IgG)1 suitable for analogous oriented immobilization of chymotrypsin was isolated from a polyclonal pig antibody against diiso‐propylphosphoryl‐(DIP)‐chymotrypsin by biospecific affinity chromatography on a Sepharose column to which chymotrypsin had been attached through a covalent bond between the surface part of the molecule around the active site and immobilized antilysine, a naturally occurring polyvalent trypsin inhibitor.
New phase supports for partition chromatography of biopolymers
Authors: Müller Werner
Published: March 2011

Liquid‐liquid partition chromatography of bio‐polymers requires aqueous two‐phase systems for reasons of sample solubility and stability. Such aqueous two‐phase systems form when thermodynamically incompatible polymers are co‐dissolved in water. The most common polymer combination providing a two‐phase system at reasonably low polymer concentrations is the combination of poly(ethylene glycol) (“PEG”) and dextran (“DX”), detected and introduced for the separation of biopolymers and cells by Albertsson about 30 years ago. The application of this powerful system for liquid‐liquid partition chromatography requires support materials with surfaces able to immobilize selectively one of the two aqueous phases. This phase immobilisation may be achieved by exploiting incompatibilities between the polymers dominating in the phases and the hydrated support surface.

Examples involving diol‐modified silica and polyacrylamide coated diol‐silica as support materials in aqueous PEG‐DX and PEG‐salt systems are presented. The application of such systems for the separation of biopolymers is demonstrated.
Current development of analytical affinity chromatography: Design and biotechnological uses of molecular recognition surfaces
Authors: Chaiken Irwin M. , Shai Yechiel , Fassina Giorgio , Caliceti Paolo
Published: March 2011

Analytical high performance liquid affinity chromatography (analytical HPLAC) has been investigated as an experimental guide to both synthetic design and affinity technological use of peptide and protein recognition surfaces. This work has progressed from the ongoing use of analytical affinity chromatography to study interaction mechanisms of naturally‐occurring peptides and proteins, including enzyme fragment complexes and neuroendocrine biosynthetic precursors. We recently initiated a study to use analytical HPLAC for de novo design of recognition peptides called “anti‐sense peptides”. Present data suggest the potential to use anti‐sense peptides as “synthetic antibodies”, in immobilized forms, for biomolecular separation and analysis. Analogous studies have been started with immobilized natural antibodies in analytical immuno HPLAC. Our present data typify the growing usefulness of analytical HPLAC when designing recognition molecules, analyzing their interaction characteristics, and devising ways to use them in affinity technology.
Selective isolation of C‐terminal peptides from proteolytic mixtures of proteins by affinity chromatography on immobilized anhydrotrypsin and anhydrochymotrypsin
Authors: Ishii Shin‐ichi , Kumazaki Takashi , Fujitani Asamichi , Terasawa Kumiko
Published: March 2011

Anhydrotrypsin in an immobilized form shows strong specific affinity for the peptides containing Arg, Lys, or S‐aminoethyl‐Cys at their C‐termini. By taking advantage of this unique property of the adsorbent, we established an efficient chromatographic procedure useful for selective isolation of C‐terminal peptides from protease digests of proteins. The utility was demonstrated in cases of a tryptic digest of Streptomyces subtilisin inhibitor in a reduced and S‐carboxymethylated form (RCM‐SSI) (with C‐terminal Phe) and of a chymotryptic digest of α1‐antitrypsin (with C‐terminal Lys): the C‐terminal peptides were recovered as the breakthrough fraction of the chromatography in the former case and as the adsorptive fraction in the latter. Immobilized anhydrochymotrypsin was also useful for selective adsorption of the C‐terminal peptide from the tryptic digest of RCM‐SSI. It was further found that immobilized anhydrotrypsin exerts strong affinity even for human oxyhemoglobin and its α‐chain (with C‐terminal Arg), but not for the β‐chain (with C‐terminal His) and hemoglobin‐haptoglobin complex. Thus the adsorbent may be applicable also to the isolation of macromolecular ligands and to the analysis of macromolecular interactions.
Immobilized metal ion affinity chromatography of proteins on IDA‐Fe3+
Authors: Sulkowski Eugene
Published: March 2011

Several proteins, selected for their varied isoelectric points within pH range ca. 4 to ca. ll, bind to immobilized (chelated to iminodiacetate) ferric ion, IDA‐Fe3+, when applied in a 50 mM buffer, pH 6.0. These proteins can be displaced from IDA‐Fe3+ columns by an increase of pH from 6 to 8, an increase of sodium chloride from 0 to 1 Malar and, in particular, by both.

Apotransferrins, in contrast to other proteins, are able to scavenge Fe3+ ion from IDA‐Fe3+.

Interestingly, two proteins, both quite acidic, behave quite differently on IDA‐Fe3+: α1‐acid glycoprotein (sialic acid) does not bind, whereas phosvitin (phosphate 1) binds avidly.

IDA‐Fe3+ sorbent, due to its unusual sorptive properties, represents a new addition of particular significance to the family of chromatographic sorbents available for protein purification.
A new kind of “thiophilic” electron‐donor‐acceptor adsorbent
Authors: Porath Jerker , Oscarsson Sven
Published: March 2011

Four simple agarose derivatives have been synthesized: 3‐(Z‐pyridylsulfido)‐2‐hydroxypropyl‐ 3‐(2‐pyridyloxy)‐2‐hydroxypropyl‐ 3‐(phenylsulfido)‐2‐hydroxypropyl‐, and 3‐(phenyloxy)‐2‐hydroxypropylagarose. Their affinities for serum proteins have been studied in the presence and absence of water‐structuring salt. About 50% of the proteins, among them immunoglobulins and α2‐macroglobulin, but not albumin, were non‐covalently adsorbed to the PyS‐gel in buffer containing 0.5 M K2SO4. These proteins are the same as those adsorbed to the so‐called thiophilic gel, T‐gel (5), but there are some additional proteins found in the adsorbate that strongly indicate a specific influence on the protein adsorption exerted by the π‐electron system of the pyridine residue. The thio‐ether sulfur appears to be a necessary structural requirement for the characteristic adsorption behaviour. Thiophilic vs. hydrophobic ligand‐protein interaction is discussed.
Studies on triazine dye‐enzyme interaction by means of affinity partitioning
Authors: Kopperschläger Gerhard , Kirchberger Jürgen , Kriegel Thomas
Published: March 2011

Affinity partitioning in aqueous two‐phase systems composed of dextran and polyethylene glycol the latter being partially replaced by dye‐substituted polymer was evaluated for the study of enzyme‐dye interaction. The method was found excellently suited for the recognition of any interaction between a certain enzyme and triazine dyes by determining the actual partition coefficient, K.

Two enzymes, intestinal alkaline phosphatase and yeast phosphofructokinase, were studied. Alkaline phosphatase binds more or less specifically to various triazine dyes. A number of substrates but also inorganic phosphate, NAD+ and selected chromophores are competing agents in enzyme‐dye interaction whereas hydrophobic and uncompetitive inhibitors fail to compete with the dye. Thus, information on the chemical nature of the dye‐enzyme interaction was obtained. Affinity partitioning turned out also appropriate to study the structural dynamics of enzymes. This was exemplified on the specific interaction of phosphofructokinase with a number of triazine dyes. A change of the allosteric properties of the enzyme in respect to ATP‐inhibition and its reversibility was indicated by a corresponding alteration of the partition coefficient. The results are discussed in terms of a conformational change of the enzyme.
Protein interactions with solid surfaces following contact with plasma and blood
Authors: Brash John L.
Published: March 2011

Two aspects of blood protein interactions with solid surfaces are discussed. The first is competitive adsorption among the many proteins in the blood. The general factors which determine the composition of the adsorbed layer in any multicomponent protein system are considered and then related to current knowledge of competitive adsorption in blood. The latter pertains largely to the so‐called Vroman effect whereby proteins are adsorbed and displaced from the surface in an ordered sequence. Secondly the possible transformation of adsorbed enzyme precursors into active enzymes by the agency of the surface is discussed. The example of the plasminogen‐plasmin system is used to illustrate this discussion.
Time‐resolved spectroscopic studies on phenyl‐substituted poly(phenylenevinylene)s by picosecond excite‐ and probe technique
Authors: Rentsch Sabine , Stolberg Klaus‐Peter , Opfermann Johannes , Hörhold Hans‐Heinrich
Published: March 2011

Photoinduced picosecond absorption spectra of poly(1,4‐phenylene‐1,2‐diphenylvinylene) (DP‐PPV) and of related oligomeric and polymeric compounds were investigated in toluene solution. Between 400 and 900 nm the rise (5 … 40 ps) and decay (40 … 300 ps) of three transient absorption bands have been observed. The low energy absorption appears with a time delay of 5 ps and has its peak at 680 nm (1.8 eV). This band position is coincident with the well known ECS radical ion (polaron) absorption and is therefore assigned to this type of photogenerated charged species. The other two absorptions appear at higher energies. One of them is situated at 2.8 eV which is near to the band edge (2.9 eV). It originates immediately with the exciting pulse and is attributed to a neutral excited state. The other one (2.7 eV) is suggested to be due to an ECS diion (bipolaron).
Laser speckle techniques: Application in polymer physics
Authors: Holoubek J. , Krug H.
Published: March 2011

The methods of measuring SP correlation are presented with examples of application to polymer solids. The system for interactive picture analysis useful for extraction of various types of physical information for both real‐ and Fourier‐space images is described.