bluuebunny/crossref_metadata_2025_split huggingface dataset:
General aspects of protein adsorption
Authors: Jennissen Herbert P. 
Published: March 2011

AbstractThe study of protein adsorption on a mechanistic and quantitative basis is still a relatively young science and a general theory encompassing all aspects cannot be given. Till now the possibility of synthesizing surfaces in a controlled way, to elucidate the mechanism of protein adsorption ‐ a possibility existing since the advent of affinity chromatography nearly two decades ago ‐ has only been utilized to a small extent. Since this technique, however, has allowed the derivation of some general principles of protein adsorption and protein adsorption kinetics, which would otherwise not have been amenable for study, these results will be mainly referred to here.
The adsorption of lysozymes: A model system
Authors: Hansen J. , Ely K. , Horsley D. , Herron J. , Hlady V. , Andrade J. D. 
Published: March 2011

AbstractHen egg white lysozyme was adsorbed onto clean borosilicate glass and n‐pentyl silane‐treated glass surfaces. Both modified (reductively methylated) and native lysozyme were studied. Variable angle X‐ray photoelectron spectroscopy (VA‐XPS) suggested differences in the nature of the adsorbed layer depending on substrate properties, as well as on degree of methylation of the protein. Adsorbed film thickness (as measured in the dehydrated state by XPS) ranged from 14 Å on hydrophilic glass to 25 Å on the hydrophobic surface. Degree of surface coverage ranged from 45% on the hydrophobic to 69% on the hydrophilic surface. The results suggest that lysozyme unfolds to a greater extent and covers more surface on the hydrophilic glass, possibly due to strong electrostatic interactions at the pH 7.4 conditions used in the study. An analysis of the surface structure of native hen lysozyme by molecular graphics has also been performed, suggesting that adsorption on hydrophobic surfaces should occur via the hydrophobic patch opposite the enzyme active site cleft.A comparison with human lysozyme has also been made using total internal reflection fluorescence (TIRF) spectroscopy to measure protein adsorption on model surfaces. The two proteins have significantly different interfacial properties.
Surface diffusion as a rate‐enhancing mechanism in macromolecular association: The effectiveness of one‐ and two‐dimensional surface sliding
Authors: Berg Otto G. 
Published: March 2011

AbstractThe effective rate for a macromolecular association can be increased if the molecules can be held together loosely by nonspecific surface forces while they search for the specific reactive sites. In this way steric constraints can be relieved. In extreme cases, a specific interaction site can be surrounded by extensive surfaces either essentially linear (e.g. a DNA site) or two‐dimensional (e.g. a membrane‐bound receptor). If ligands can bind nonspecifically and search these surfaces in a lower‐dimensional diffusion process, very substantial rate enhancements can be achieved under suitable conditions. The ranges of concentration and affinity of such nonspecific surfaces that can produce rate enhancements are derived and discussed. It is found that under the expected conditions in the living cell, such rate enhancements will be fairly modest. Nonetheless, nonspecific surface diffusion may play an important role.
Procedure for activating polymers with primary and/or secondary hydroxyl groups
Authors: Ngo That T. 
Published: March 2011

AbstractA new facile method using 2‐fluoro‐1‐methylpyridinium toluene‐4‐sulfonate (FMP) for activating polymeric hydroxyl groups has recently been developed (Refs. 1–2). Such activated polymers are useful for immobilization of enzymes, antibodies and other biomolecules and for affinity matrix development. The activation method involves reacting, at room temperature, the polymer with FMP in the presence of a tertiary amine for 0.5 to 1 hour. The activated hydroxyls react readily with nucleophiles, such as amino or thiol ligands at pH 5–10. The resulting linkages between the ligand and the polymer are respectively stable secondary amine and thioether bonds. The activated polymer remains active and usable for several months when stored at 4°C in either an acidic aqueous solution or an inert anhydrous organic solvent. The “half‐life” of the activated groups in non‐nucleophilic buffer solution varies from 10 to 300 hours in the pH range of 10 to 6, being most stable at low pH. Both primary and secondary hydroxyl groups of different polymers were facilely activated and shown to react readily with nucleophilic groups of biomolecules. Furthermore, FMP provides a convenient handle for the synthesis of unique conjugates consisting of FMP and a guiding molecule. These conjugates function as an activator of the hydroxyl group of a solid support as well as a molecular guide which orients the position of the ligand to be immobilized. The conjugates make it possible to immobilize ligands in an affinity‐directed way.
Exposure of hydrophobic sites in CA2+‐binding proteins: Influence on chromatographic properties and structure‐function relationships
Authors: Krebs Joachim , Buerkler Jacqueline , Guerini Danilo 
Published: March 2011

AbstractCalmodulin and related Ca2+ ‐binding proteins were characterized using different labeling, chromatographic and spectroscopic techniques. Ca2+‐binding to members of the so‐called “EF‐hand”‐ or “helix‐loop‐helix”‐model protein family induced conformational changes, thereby exposing hydrophobic sites in some of them. These sites were identified using the photoreactive, carbene‐generating, radioactive probe 3‐(trifluoromethyl)‐3‐(m‐[1251]iodophenyl)diazirine, and characterized using different high performance liquid chromatography techniques. The influence of chemical modification of some of the amino acid residues on the properties of calmodulin were characterized using circular dichroism. A correlation between an increase of oxidized methionine residues of calmodulin and a decrease of Ca2+‐induced helical content was observed.
Immunoaffinity separations of cells in two polymer aqueous phase systems
Authors: Brooks Donald E. , Sharp K. A. , Stocks S. J. 
Published: March 2011

AbstractTwo phase systems based on aqueous mixtures of polymers such as dextran and poly(ethylene glycol) have proven to be useful in the separation of cells via partition. By suitably modifying antibodies raised against cell surface antigens so that they partition strongly in favour of one of the phases it is possible to produce selective isolations of antigenically specified cells. Derivatization of a secondary antibody which recognizes the constant region of a class of primary antibodies provides a more generally useful immunoaffinity reagent. The theory of affinity partitioning of ideal species predicts extremely large increases in partition as the result of binding of affinity ligands. Results to date indicate effects smaller than predicted by theory, however, suggesting that the polymers and other modifying agents used to change the partition behaviour of the antibodies behave non‐ideally.
Molecular recognition and signal processing in biosensors
Authors: Scheller Frieder W. , Schubert Plorian , Weigelt Dietmar , Mohr Peter , Wollenberger Ulla 
Published: March 2011

AbstractThe specificity of molecular recognition is reflected to a high degree by the selectivity of the respective biosensor response. Therefore, the application of highly specific enzymes offers advantages for analytical purposes. Using lactate monooxygenase in combination with lactate dehydrogenase and pyruvate kinase, sequentially acting enzyme electrodes for lactate, pyruvate, ADP and enzyme activities, e.g. lactate dehydrogenase, creatine kinase and aminotransferases were developed. A high sensitivity was achieved based on the cycling enzyme pairs hexokinase/pyruvate kinase for ATP and ADP, and lactate monooxygenase/malate dehydrogenase for malate and oxaloacetate, respectively. On the other hand, in a sensor for a large group of substances, the unspecific microsomal cytochrome P‐450 system was applied.
Genetic approaches to protein purification
Authors: Uhlén Mathias , Abrahmsén Lars , Moks Tomas , Nilsson Björn 
Published: March 2011

AbstractA gene fusion system based on the protein A gene from Staphylococcus aureus has been developed to facilitate purification of recombinant proteins, both in large and small scale. Due to the strong interaction with IgG, it is possible to recover gene products fused to various protein A derivatives, in a one‐step procedure with high yield and in purity. Site‐directed mutagenesis was used to introduce enzymatic and chemical cleavage sites at the fusion point between the protein A derivative and the desired protein. The protein A “tail” can thereby be removed from the affinity purified fusion protein by the appropriate cleavage, releasing biologically active molecules. Recently, the system was improved by designing a synthetic DNA fragment encoding two IgG‐binding domains derived from staphylococcal protein A which are resistant to various chemical cleavages. The gene fusion product is secreted to the culture medium of E.coli and can be recovered simply by passing the clarified culture medium through an IgG Fast Flow Sepharose. The system has been used to immobilize enzymes, to obtain monoclonal and polyclonal antibodies and to produce biologically active human peptide hormones in pilot plant scale.
Characterization of dilute polymer solutions and dispersions by dynamic light scattering ‐exemplified by polystyrene and photographic emulsions‐
Authors: Helmstedt Martin 
Published: March 2011

AbstractA survey of light scattering methods in the field of polymer characterization and an introduction into fundamental relations of quasielastic light scattering are given. The partially home made RAYLEIGH spectrophotometer and its calibration is described. For monodisperse polystyrene dispersions a maximum deviation of 2 % is obtained. The translational diffusion coefficients of approximately monodisperse linear polystyrene samples dissolved in cyclohexane under theta conditions at 34.5 degrees C agree well with the relation of PETRUS et al., D0 = 1.388 · 10−4 M−0.5. Over a broad range of molecular masses the values measured in 2‐butanone at 25 degrees C give the relation D0 = 6. 16 · 10−4M−0.577 with a small deviation from earlier published data. Results for the growth of silver halide particles during the preparation of photographic seed emulsions are given.
Photon correlation spectroscopy of compatible polymer blends
Authors: Fytas G. , Kanetakis J. 
Published: March 2011

AbstractThe dynamics of concentration fluctuations in compatible polymer mixtures can be investigated by dynamic light scattering. The experiment yields both the dynamic and static structure factors from which the mutual diffusion coefficient and the segment‐segment interaction parameter can be obtained. Examples of applications are the unentangled blends poly(ethylene oxide/poly(propylene oxide) and polystyrene/poly(phenylmethylsiloxane) in the one phase region.
Miscibility and phase separation in polymer blends studied by laser light scattering
Authors: Kammer W. H. , Kressler J. 
Published: March 2011

AbstractIn this paper major emphasis has been placed on the phase behavior of miscible polymer blends, especially on blends containing random copolymers. Blends containing random copolymers generally tend to phase separation at elevated temperatures (LCST behavior). Experimental determination of miscibility areas as a function of temperature and copolymer composition by laser light scattering provides the interaction parameters necessary for theoretical explanations and predictions of various phase separation phenomena.Just above the LCST polymer blends exhibit regular highly interconnected two‐phase morphologies. The rate of decay of these structures is estimated. The phase separation kinetics can be pursued by laser light scattering and is discussed in terms of CAHN's linearized theory. It can be shown that the linear theory adequately describes the early stage of phase decomposition. The linear theory is also applicable to the reverse phenomenon, the phase dissolution below LCST. unlike the case of phase separation the diffusion‐controlled regime is that in the late stage of phase dissolution.
Raman spectroscopy in high polymer research and production
Authors: Steger Walter Eberhard 
Published: March 2011

AbstractThe mechanism of RAMAN scattering depends on molecular polarizability changes and therefore this method is especially useful for the study of non‐polar bonds. This is shown by reviewing some analytical applications. Knowledge on polymer structure was especially promoted by studies of the lowest‐frequency bending modes, of correlation splittings in case of crystallinity, and by measurements on depolarization of the laser light. RAMAN spectroscopy has possibilities for in‐situ and multi‐method measurements. Newer developments serving the polymer sciences are surface enhanced RAMAN scattering and the RAMAN spectroscopy of electroconducting polymers.
Laser pulse fluorometry as a tool in polymer research
Authors: Boens Noël , De Schryver Frans C. , Ameloot Marcel 
Published: March 2011

AbstractA time‐resolved fluorescence spectrometer with laser excitation and picosecond time‐correlated single photon counting detection is described. The parameter recovery from experimental data is discussed in detail. Correction methods for errors in the time‐correlated single photon counting technique are indicated. Applications of this photophysical tool to polymer research are given.
Time‐resolved optical absorption spectroscopy of molten polyethylene blends
Authors: Brede Ortwin , Hermann Ralf , Helmstreit Wilfried , Taplick Thomas , Stephen Ludwig 
Published: March 2011

AbstractBy means of pulse radiolysis and laser photolysis experiments with detection by optical absorption spectroscopy short‐living radical transients in pure PE and in PE doped with additives (e.g. di‐>tert‐butyl‐p‐cresol, diphenylamine, benzophenone and carbon tetrachloride) were characterized by their optical absorption spectra and kinetics. It was found that the additive radicals were formed in a very fast process probably via exciton migration and subsequent energy transfer and dissociation reactions.
Time resolved laser spectroscopy of excited state processes in photoinduced polymerization reactions
Authors: Fouassier Jean‐Pierre 
Published: March 2011

AbstractDuring the last years, the use of photoinduced radical chain polymerization of unsatured monomers has increased considerably because of the vide applications of these processes in photoactive polymer‐based systems. The present paper is mainly concerned with an investigation of the processes involved. For this purpose, time resolved laser spectroscopy (which appears to be a very convenient method for investigating directly the experimental behaviour of selectively excited chromophores) has been used. The utility of such a technique for the investigation of the primary processes which occur in the excited states of the photoinitiators immediately after the absorption of photons is demonstrated. As examples, main outlines corresponding to the classical processes observed in radical photoinitiated polymerization are considered and discussed: excited state processes in photoinitiators; mechanism of excitation transfer in combination of photosensitive systems; visible laser light induced polymerization; holographic recording.
Laser induced polymerization of acetylene derivatives
Authors: Karpacheva Galina , Khoroshilova Valentina , Davydov Boris 
Published: March 2011

AbstractHe‐Cd laser induced polymerization of aryl‐propargylamines such as phenyl‐ and diphenylpropargylamines were studied. The polymerization of these monomers was shown to be realized only in presence of acceptor of electrons. Polymer formation process is based on the formation of an intermediate compound and its following polymerization by the radical reaction of C≡C bond. Photochemical and photophysical processes leading to the formation of intermediate compound were investigated. The polymers obtained were characterized by IR‐, ESR‐, NMR‐spectroscopy. The conjugated double bond system formation is the main characteristic of these polymers. Some polymer properties were studied.
Advances in ultra‐high load polymer‐supported peptide synthesis with phenolic supports: 2. Use of ‘hydrazinolysis‐hplc’ to check for racemization on c‐terminal amino acid loading and to determine peptide homogeneity during synthesis with selectively labile c‐terminal anchoring linkages
Authors: Baker Philip A. , Coffey Andrew F. , Epton Roger , Johnson Tony , Mole Edward J. 
Published: March 2011

Abstract2, 4‐Dinitrophenyl‐L‐phenylalanine has been coupled to L‐, D‐, and DL‐amino acid phenyl esters pendant upon a polymer matrix. The esters had been prepared by di‐isopropylcarbodiimide‐mediated condensation, catalyzed by 4‐dimethylaminopyridine. Reverse phase high pressure liquid chromatography (HPLC), using elution solvents consisting of 10 vol.‐% trifluoroacetic acid in water/acetonitrile mixtures, has been used to investigate the 2,4‐dinitrophenyl L‐L and L‐D dipeptide mixtures obtained on hydrazinolysis of each of the dipeptide‐matrix assemblies. ‘Hydrazinolysis‐HPLC’ has been used also to determine intermediate peptide homogeneity in ultra‐high load solid (gel) phase synthesis with Boc amino acids. Cross‐linked poly(N‐[2‐(4‐hydroxyphenyl)ethyl]acrylamide) and two derived polymers incorporating spacer groups have been used as supports. The spacer groups made possible peptide C‐terminal attachment by either HF‐labile benzyl ester or HF‐labile cyclohexyl ester bonds, while still incorporating the phenolic ester linkage susceptible to rapid hydrazinolytic scission.
Crosslinked polyacrylamide‐hydrazide (paah) as matrix for the gel entrapment of cells and enzymes ‐ an overview
Authors: Freeman Amihay 
Published: March 2011

AbstractThe development and use of a gel entrapment technique designed for the immobilization of viable, sensitive cells is described. The method is based on the controlled chemical cross‐linking of prepolymerized, linear polyacrylamide partially substituted with acylhydrazide groups, by glyoxal. The methodology, applications and advantages of this technique for the immobilization of cells and enzymes by gel entrapment are reviewed.
Surface structure of polymers for biomedical applications
Authors: Ratner Buddy D. 
Published: March 2011

AbstractBiological reactions with synthetic polymers are strongly influenced by the surfaces of those materials. The surfaces are often substantially different in composition and structure from the bulk. By using contemporary surface analysis methods, we can understand polymer surfaces. The surfaces of polymers can also be modified to generate desired biological responses. These points are illustrated with examples involving polyurethanes and RF plasma‐deposited films.
Polyanhydrides: Stability and novel composition
Authors: Domb A. , Langer R. 
Published: March 2011

AbstractNew types of polyanhydrides with advantageous properties with respect to biomedical use were synthesized. The first are aliphatic‐aromatic homopolyanhydrides of the structure: ‐(OOC‐C6H4‐O(CH2)x‐ CO‐)n (=1−10). These polymers display a zero‐order hydrolytic degradation profile for two to ten weeks, the time period of degradation is a function of the length of the aliphatic chain. Stability studies under anhydrous conditions showed that these polymers underwent reversible self‐depolymerization in chloroform but were stable in solid state for over 6 months at 25°C.The second type of polymer, unsaturated polyanhydride of the structure: [‐(OOC‐CH=CH‐CO)x‐(OOC‐R‐CO)y‐]n, have the advantage of secondary polymerization of double bonds to create a crosslinked matrix. These polymers were prepared from the corresponding diacids polymerized by melt condensation or in solution. Molecular weights of up to 44 000 and 30 000 were achieved for polyanhydrides of p‐carboxyphenoxyalkanoic acid and fumaric acid, respectively.
Ueber die anwendung von in vivo zersetzbaren polymeren in der thoraxchirurgie
Authors: Nakamura Tatsuo , Shimamoto Takeshi , Watanabe Satoshi , Shimizu Yasuhiko , Hyon Suong‐Hyu , Ikada Yoshito 
Published: March 2011

AbstractBioabsorbable materials for use in a clinical situation are required to have specific mechanical characteristics and predictable degradation. We have been studying the mechanical properties and the bioabsorbability of polyesters of aliphatic α‐hydroxyacids, such as polylactide, polyglycolide (PGA) and their copolymers, to applying them for surgery, and classifying the effects of the factors governing their biodegradation behavior.Poly‐L‐lactide (P‐L‐LA) showed slow degradation and maintained initial mechanical properties for a period of more than 3 months after implantation. In contrast, PGA showed rapid degradation and after its absorption at the site of implantation, good replacement of the tissue was observed. On th basis of these results, various clinical applications for thoracic surgery were evaluated as follows: 1) For the fixation of fractured ribs, pins made from either P‐L‐LA or a composite of P‐L‐LA and hydroxyapatite were prepared. 2) For reconstruction of the chest wall, Tricot‐Knit PGA mesh and P‐L‐LA mesh were fabricated.In vivo tests in dogs were then carried out. P‐L‐LA pins maintained the strength required for connecting the fractured ribs until complete reunion was achieved, while the meshes acted as scaffolding for reconstruction of the connective tissue. In both cases, these materials showed minimal tissue reaction and sufficient biocompatibility.
Surfacial modification of polymer powders as drug carriers
Authors: Matsubara Yoshio , Yagi Tooru , Yamashita Natsuki , Maeshima Toshihisa 
Published: March 2011

AbstractPreparation of warfarin methacrylate(WaMA) was carried out by esterification of warfarin as thromboembolism drug with methacryloyl chloride. Radical copolymerization of WaMA with 1‐vinyl‐2‐pyrrolidone(VPr) was carried out in 1,4‐dioxane at 60°C using 2,2′‐azoisobutyronitrile as initiator. The surfacial modification of the copolymer powders was achieved using the freeze‐drying by dissolving the copolymer in benzene and micellation by benzene‐in‐water and water‐in‐benzene systems. The hydrolysis of the copolymer including the drug was investigated under mild condition from a view point of released rate of the drug.