bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Oligo(3‐hydroxybutanoate)(OHB)‐Containing Peptides with High Binding Affinity to a Class‐I‐MHC Protein
Authors: Seebach Dieter , Poenaru Sorana , Folkers Gerd , Rognan Didier 
Published: December 2004

AbstractIn the center of the immune system, there are major histocompatibility (MHC) protein/nonapeptide complexes which are recognized by T cell. The nonapeptides consist of three regions, an N‐terminal one containing three amino‐acid residues with a mandatory arginine in position 2, a C‐terminal one with a lysine or arginine in position 9, and a central, variable one of five residues (cf. Fig. 1). We have now synthesized the first conjugates (1–4) of oligopeptides with oligo[(R)‐3‐hydroxybutanoates] (OHB) as analogs of MHC‐binding peptides. Of the approaches chosen (Scheme 1), a fragment coupling of a hydroxy‐butanoyl‐amido ester (17 and 19) with an [(aminoalkanoyl)oxy]butanoyl chloride (27; Scheme 3), followed by two peptide‐coupling steps (Scheme 4), turned out to be most efficient. The conjugates H‐Gln‐Arg‐Leu‐(HB)3,4‐Lys‐OH (1 and 2) and H‐Ala‐Arg‐Leu‐(HB)3,4‐Lys‐OH (3 and 4) were thus obtained in pure form. The conjugates 1 and 2 with N‐terminal glutamine have a tendency to undergo cyclization with formation of a pyroglutamate residue (ef. Fig. 2). CD Measurements at different temperatures and so‐called epitope‐stabilization assays show that the complexes of the conjugates 2 and 4, containing four HB units, with the HLA‐B27 class‐I‐MHC protein are more stable than those of a model nonapeptide (C50 values of 2.25 and 1.60 μM vs. 10 μM), while the conjugates 1 and 3 with three HB units incorporated form less stable complexes (C50 values of 30 and 21 μM). The tetra(hydroxybutanoate)‐peptide conjugates 2 and 4 are the first nonapeptide analogs for which the modification of the central part leads to increased affinities for a class‐I‐MHC protein, as compared to a model nonapeptide.
A Novel and Efficient Synthesis of 14‐Alkoxy‐Substituted Indolo‐ and Benzofuromorphinans in the Series of Selective δ Opioid Receptor Antagonists
Authors: Schmidhammer Helmut , Schwarz Peter , Wei Zhong‐Yong 
Published: December 2004

AbstractA novel and more efficient synthesis of 14‐alkoxy‐substituted indolo‐ and benzofuro‐morphinans in three steps starting from either naltrindole (1) or naltriben (2), using methoxymethyl or silyl protecting groups, is reported. The 14‐O‐alkyl group is introduced at the penultimate step of the procedure. This is an additional advantage of the described procedure since the late introduction of the 14‐O‐alkyl group makes it much easier to produce a greater diversity of 14‐alkoxy derivatives in this series of δ opioid receptor antagonists. Thus, compounds 14–19, 20–25, and 27–29 were synthesized.
Synthesis of Thiophene‐Substituted 3H‐Naphtho[2,1‐b]pyrans, Precursors of Photomodulated Materials
Authors: Moustrou Corinne , Rebière Nicole , Samat André , Guglielmetti Robert , Yassar Abd Errahim , Dubest Roger , Aubard Jean 
Published: December 2004

AbstractThe synthesis of 3H‐naphtho[2,1‐b]pyrans 9–21 linked to a thiophene moiety is described. Two different synthetic approaches were applied to prepare these novel functionalized compounds, and their spectrokinetic properties in solution are reported.
Theoretical Parameters to Characterize Antioxidants. Part 2. The cases of melatonin and carvedilol
Authors: Migliavacca Eugenia , Ancerewicz Jacek , Carrupt Pierre‐Alain , Testa Bernard 
Published: December 2004

AbstractThis theoretical study focuses on two indole derivatives, melatonin (1) and carvedilol (8), with the objective of improving our understanding of the molecular mechanisms underlying their radical‐scavenging activity. Quantum‐mechanical calculations were carried out using the AM1 semi‐empirical method, some results being confirmed by ab initio (3‐21G) calculations. The quantum‐chemical descriptor Δ Hox (relative adiabatic oxidation potential) and the shape of the SOMO (singly occupied molecular orbital) indicate that the stabilization of its radical cation can partially explain the well‐documented antioxidant efficacy of melatonin. This stablization may result from electrostatic interactions and from a hyperconjugative effect existing in a family of conformers of the melatonin radical cation having the side chain almost perpendicular to the plane of the aromatic rings. Furthermore, 6‐hydroxymelatonin (7) appears to be a better free‐radical scavenger than melatonin (1) in agreement with experimental results. According to the theoretical parameters Δ Hox and Δ Habs (relative bond dissociation enthalpy), carvedilol (8) is not a good antioxidant, in contrast to its ring‐hydroxylated metabolites whose powerful antioxidant effects are explained by the formation of an oxyl radical stabilized by delocalization over the carbazole nucleus.
Lipase‐Catalyzed Acetylation of 3‐Substituted 2,3‐Dihydro‐1H‐1,4‐benzodiazepin‐2‐ones: Effect of temperature and conformation on enantioselectivity and configuration
Authors: Avdagić Amir , Lesac Andreja , Majer Zsuzsa , Hollòsi Miklòs , Šunjić Vitomir 
Published: December 2004

AbstractEnantioselectivity of acetylation by vinyl acetate/AcOEt catalyzed by immobilized Candida antarctica lipase (Novozym 435) is studied for rac‐3‐(hydroxymethyl)‐1,4‐benzodiazepin‐2‐ones 7, 9, 14 (n = 1; number of CH2 groups in the chain at C(3)), 20 (n = 2), and for prochiral 3,3‐bis(hydroxymethyl) derivative 16. Enantiomeric excess (ee [%]) is correlated with conformational properties of substrates (relative conformation, energy difference between two boat‐like ground‐state conformations, ring‐inversion barrier) as determined by DNMR and MM2 calculations. (3S)‐Enantiomers of acetates (+)‐8, (+)‐10, (+)‐15, and (+)‐21 were preferentially formed. In the case of the acetate (−)‐17 (ee 90.2%), formation of the (3R)‐enantiomer was favored. C(3)OH Group with hemiaminal‐like character in rac‐3 (n = 0) cannot be acetylated by any of 23 tested lipases and four esterases. For racemic alcohols 7, 9, 14, and 20, preferred acetylationof the (3S)‐enantiomers, present in solution in absolute (M)‐conformation, was established; only in prochiral diol 16 (n = 1) the CH2OH group in the (pro‐R)‐position is prevalently acetylated, presumably due to the binding to the enzyme, in absolute (P)‐conformation. Temperature dependence of enantioselectivity revealed inverse correlation of the E value of rac‐9, and ee values for prochiral 16, with T[K], indicating prevalent contribution of the enthalpy term to enantioselection. Absolute conformation (M/P) and absolute configuration at C(3) of all products was determined by combining CD and 1H‐NMR data.
The effect of the cooling rate of dental alloys on their amalgamation properties
Authors: Johnson L. B. , Carwile A. C. 
Published: December 2004

AbstractSilver–tin alloys of various compositions (60–80 atomic % Ag) have been prepared from the melt using cooling rates from about 50°C/hr to about 106°C/sec. Structural differences due to the different cooling rates were shown by metallographic and x‐ray diffraction techniques. From each composition and cooling rate, powders were then prepared and amalgamated. The amalgams were tested for Hg content, dimensional change during setting, and tensile strength. Changes in cooling rates had some effect on the relative amounts of phases present but primarily affected the grain sizes. In general, the faster the cooling rate, the smaller the grain size; the smaller the grain size, the faster and more uniform the amalgamation; the more uniform the amalgamation, the stronger the amalgam. Storage of the alloy powders at room temperature slowed their amalgamation rates, destroyed their uniformity, and resulted in weaker amalgams. However, no phase changes were observed by x‐ray diffraction in the freshly comminuted alloys after aging at room temperature for two months.
The effect of shear, specific surface, and air interface on the development of blood emboli and hemolysis
Authors: Solen Kenneth A. , Whiffen James D. , Lightfoot Edwin N. 
Published: December 2004

AbstractHeparinized dog blood was exposed to shear and foreign surfaces in conicylindrical test cells. The cells were injection molded from polycarbonate and were filled using a technique that avoided contact of the blood with air. Particulate‐matter formation was measured and was found to be dominated by the surface‐to‐blood–volume ratio and to be independent of shear rate. Hemolysis was also measured and was found to vary linearly with shear rate and to increase with increasing surface‐to‐blood volume ratio. Thus, at low shear rates and high specific surface conditions, the degree of hemolysis was found to be minimal while particulate‐matter formation was high. The results suggest that the safety of extracorporeal perfusion procedures cannot be inferred from hemolysis measurements alone. In one series of tests, a gas–blood interface was generated at a rate equivalent to the rate of surface renewal in conventional disc oxygenators. The gas–blood interface failed to contribute significantly to the damage indices, which suggests that the apparent superiority of membrane oxygenators may be a result of factors other than the absence of a blood–gas interface.
Biocompatibility tests of components of an implantable cardiac assist device
Authors: von Recum Andreas F. , Imamura Hiroji , Freed Paul S. , Kantrowitz Adrian , Chen Shan‐Te , Ekstrom Merlin E. , Baechler Charles A. , Barnhart Marion I. 
Published: December 2004

AbstractA permanently implantable in‐series left ventricular assist device, the dynamic aortic patch (DAP), has been tested in chronic animal experiments. The DAP replaces a section of the intrathoracic aortic wall. Hemothorax and hematocele at the implantation site have been complications in recent experiments. Primary postoperative hemorrhage was ruled out, and the biocompatibility of all components was therefore examined. Dacron velour, Teflon felt, conductive polyurethane, segmented polyether polyurethane, and Teflon‐coated polyester fiber sutures were implanted in the pleural cavities of dogs and tested in vitro by culturing canine saphenous vein explants on them. In vivo experiments demonstrated that all components elicited mild to moderate inflammatory reactions, but hematocele occurred only when the components were implanted in the aorta with direct blood contact and exposed to arterial blood pressures. In vitro, cells were cultured on all components with no signs of toxic reactions. These results indicated that the host tolerated all implant components without major inflammatory responses. However, histological data indicated that chronic slow bleeding into or through the Dacron velour in contact with the arterial blood serum could account for hemothorax or hematocele formation. Therefore, a configuration of the assist device using materials impermeable to blood may obviate these difficulties.
Histopathology and metallurgical analysis of a removed Lane plate at 53 years postimplantation: A case report
Authors: Tarr Richard R. , Jorge Rolando , Latta Loren L. , Ghandur‐Mnaymneh Latifa 
Published: December 2004

AbstractA vanadium steel Lane plate with nickel coating and low grade steel screws were removed from a patient 53 years postimplantation. Corrosion of the parts was extreme, but the reaction in the surrounding tissues was surprisingly quiescent under the circumstances. By today's standards, the materials, their application, and their performance were totally unacceptable. However, the biological system tolerated this “insult” well.
Water sorption and mechanical properties of 2‐hydroxyethyl‐methacrylate and methylmethacrylate copolymers
Authors: Migliaresi C. , Nicodemo L. , Nicolais L. , Passerini P. , Stol M. , Hrouz J. , Cefelin P. 
Published: December 2004

AbstractRandomly cross‐linked copolymers of 2‐hydroxyethyl‐methacrylate (HEMA) and methyl‐methacrylate (MMA) have been prepared and studied in the dry and swollen state. Tensile and indentation tests indicate that by changing the composition of copolymers, it is possible to obtain materials with a wide range of mechanical properties and corresponding glass transition temperatures. Water diffusion coefficients in sorption and desorption experiments have been calculated and compared.
Biodegradable PEO/PLA block copolymers
Authors: Cohn Daniel , Younes Hani 
Published: December 2004

AbstractPoly(ether ester) block copolymers based on polyethylene oxide (PEO) and polylactic acid (PLA) segments were synthesized and characterized, with the aim of developing a new family of bioabsorbable polymers. The materials developed were tailored to meet various mechanical and degradation requirements, and overcome the limitations of the few existing biodegradable polymers. The copolymeric matrices were characterized by means of infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance spectroscopy. The composition of the copolymers synthesized varied between 20 and 84 mol% lactic acid, with PEO chains in the 600–6000 molecular weight range. The solubility properties of the copolymers in a series of organic solvents are described. The equilibrium water content and the water contact angle of various matrices were determined and related to their composition and structure. The incorporation of PEO into the chain yielded highly hydrophilic materials, with equilibrium water contents higher than 60%. Stress/strain curves are presented.
Characterization of alkyl grafted polyurethane block copolymers by variable takeoff angle X‐ray photoelectron spectroscopy
Authors: Grasel Timothy G. , Castner David G. , Ratner Buddy D. , Cooper Stuart L. 
Published: December 2004

AbstractVariable takeoff angle x‐ray photoelectron spectroscopy was used to determine the surface composition of five polyurethane block copolymers. The high‐resolution C1s spectra from all five polyurethane samples had peaks at binding energies of 285.0, 286.5, and 289.5 eV, which are consistent with the presence of hydrocarbon, ether, and urethane carbon species. Both the measured elemental compositions at the low takeoff angles (deepest sampling depths) and the calculated elemental compositions for depths > 15 Å generally showed good agreement with the expected bulk compositions. The outer 15 Å of the surface of all five samples was depleted in the nitrogen‐containing hard segment. For the base polyurethane sample in this series, an enrichment of the poly(tetramethylene oxide) soft segment and the presence of an organic silicone impurity were detected. Doubling the chain length of both the hard and soft segments resulted in a further decrease of the hard segment concentration in the outer surface of the sample. The grafting of C2 and C18 alkyl groups onto 10 or 20% of the ure‐thane linkages resulted in an increase in the percentage of aliphatic carbon species present on the surface. In the case of the C18‐alkylated material, the presence of alkyl chains at the surface was inferred using contact angle measurements.
Adherence of coagulase‐negative staphylococci to heparin and other glycosaminoglycans immobilized on polymer surfaces
Authors: Paulsson Marianne , Gouda Ibrahim , Larm Olle , Ljungh Åsa 
Published: December 2004

AbstractThe adherence of clinical isolates of staphylococci to surfaces immobilized with various glycosaminoglycans (GAGs) was studied. In general, cells of strains of coagulase‐negative (CNS) staphylococci showed a greater adherence to polyethylene surfaces than did cells of Staphylococcus aureus, as studied by bioluminescence. When the surface was heparinized, the adherence of staphylococcal cells decreased, but CNS cells still adhered in greater numbers than did cells of S. aureus. The adherence of CNS to serum‐coated heparinized surfaces was of the same magnitude, or increased compared with nonheparinized surfaces. When the surfaces were preasorbed with different proteins with known heparinbinding domains, i.e., vitronectin, fibronectin, laminin, or collagen, the S. epidermidis cells showed higher binding to heparinized surfaces than to nonheparinized ones, and also in greater numbers than did other staphylococcal cells. Different CNS strains showed a greater ability to agglutinate polystyrene beads immobilized with heparin than did S. aureus. The adherence of S. epidermidis strain 3380 to polyethylene coated with various GAGs such as heparin and chondroitin, dextran, dermatan, and heparan sulfate was shown to be pH‐dependent, with the highest adherence at pH 7.2. This may indicate that CNS have the ability to bind to other domains of host proteins when they are adsorbed to heparinized surfaces, versus to nonheparinized ones. © 1994 John Wiley & Sons, Inc.
Synthesis, surface, and cell‐adhesion properties of polyurethanes containing covalently grafted RGD‐peptides
Authors: Lin Horng‐Ban , Sun Wen , Mosher Deane F. , García‐Echeverría Carlos , Schaufelberger Kenneth , Lelkes Peter I. , Cooper Stuart L. 
Published: December 2004

AbstractIn an attempt to improve endothelial cell adhesion and growth on a polyurethane copolymer, cell adhesive RGD‐containing peptides were grafted to the polymer backbone. Two peptide grafting reaction schemes, including one‐step and two‐step approaches, were developed. FTIR and amino acid analysis confirmed that coupling of the peptide to the polyurethane backbone was achieved by both the one‐step and two‐step methods. However, the two‐step approach showed a higher peptide coupling efficiency and resulted in better control of the orientation of the grafted peptide. The two‐step reaction scheme was used to prepare Gly‐Arg‐Gly‐Asp‐Ser‐Tyr (GRGDSY), Gly‐Arg‐Gly‐Asp‐Val‐Tyr (GRGDVY), and Gly‐Arg‐Gly‐Glu‐Ser‐Tyr (GRGESY) peptide‐grafted polyurethanes with two different peptide densities (100 and 250 μmol/g polymer). Dynamic contact angle measurements indicated that the surfaces of the peptide‐grafted polyurethanes were more hydrophilic than the starting and carboxylated versions of the precursor polyurethane. In addition, the surface hydrophilicity of the peptide‐grafted polymers increased with increasing bulk peptide density. Electron spectroscopy for chemical analysis suggested that the grafted peptide was present at the polymer—air interface, in vacuo, for the peptide‐grafted polyurethanes. The surface peptide density appeared to correlate with the incorporated peptide density in the bulk. In vitro endothelial cell adhesion experiments showed that, without the presence of serum in culture medium, the GRGDVSY‐ and GRGDVY‐grafted polyurethanes dramatically enhanced cell attachment and spreading compared with the starting, carboxylated, and GRGESY‐grafted polymers. Increasing the peptide density from 100 to 250 μmol/g polymer for the GRGDSY‐ grafted polyurethanes resulted in an increase in cell attachment. With approximately the same peptide density (100 or 250 μmol/g polymer), the GRGDVY‐grafted polymers supported more adherent cells than did the GRGDSY‐grafted polymers. Similar trends were observed in the in vitro endothelial cell growth studies using culture medium containing serum and endothelial cell growth supplement. The GRGDSY‐ and GRGDVY‐grafted polyurethanes promoted more cell growth than did the starting polyurethane. However, the presence of adhesive serum proteins and growth factor diminished the differences between the cell‐adhesive peptide grafted polymers and the GRGESY‐grafted polymers. © 1994 John Wiley & Sons, Inc.
Degradation of polyetherurethane by subcutaneous implantation into rats. I. Molecular weight change and surface morphology
Authors: Xi Tingfei , Sato Michio , Nakamura Akitada , Kawasaki Yasushi , Umemura Takashi , Tsuda Mitsuhiro , Kurokawa Yuji 
Published: December 2004

AbstractTwo kinds of polyetherurethane (PEU), U‐3 and U‐8, were coated in thin layers on an ethylene‐vinylalcohol copolymer (EVAL) film 0.1 mm thick. U‐3 is a nonsegmented PEU prepared from 4,4′‐diisocyanatodiphenylmethane (MDI) and poly(tetramethylene oxide) of Mn = 1,000 (PTMO 1000), and U‐8 is a segmented PEU prepared from MDI, PTMO 1000, and 1,4‐butanediol. The coating thicknesses were 0.0068 and 0.022 mm for U‐3 and U‐8, respectively. These coated films were implanted subcutaneously into rats and retrieved after various weeks. The coatings on the retrieved samples were dissolved in tetrahydrofuran (THF), and the average molecular weight (MW) was determined by injecting the THF solution into a gel permeation chromatograph. In the case of U‐3, MW increased after 2 weeks, then decreased over the implantation period. After 10 weeks, U‐3 almost disappeared from the base film. In the case of U‐8, MW reached the maximum at 4 weeks postimplantation then decreased gradually over the implantation period. The rate and degree of MW change were greater in U‐3 than in U‐8. Here, we argue that, in the early stage, low molecular weight PTMO/MDI oligomers leached out from the PEUs to the inflammatory exudate to increase MW, and in the later stage macrophage attachment/activation had a role in the degradation of PEUs. The surface morphologic changes observed by scanning electron microscopy are also discussed. © 1994 John Wiley & Sons, Inc.
Biocompatibility of a biodegradable matrix used as a skin substitute: An in vivo evaluation
Authors: Beumer G. J. , van Blitterswijk C. A. , Ponec M. 
Published: December 2004

AbstractSynthetic biodegradable polymeric matrices, with a dense top layer and porous under‐layer, made of a (poly)ether/(poly)ester (PEO:PBT) copolymer called PolyactiveTM, and also of poly‐L‐lactide (PLLA), are under investigation as part of a cell‐seeded skin substitute for third‐degree, large‐scale skin defects. The biocompatibility of subcutaneously implanted matrices representing large body surface areas, were studied at 2, 4, 13, 26, and 52 weeks in rats. To investigate local or systemic effects, the weight development of the complete animal and of their hearts, kidneys, lungs, livers, and spleens, as well as the macroscopic and histologic appearance of the implants and organs, were monitored. Early inflammatory response was associated with surgical implantation trauma. All matrices showed neovascular and fibrous tissue ingrowth into the porous underlayer within 2–4 weeks after implantation. Copolymeric and PLLA matrices increasingly fragmented and liquified. After 1 year, small polymeric fragments embedded in fibrous, vascularized tissue could be retrieved at the implantation site. No systemic effects of the implants on the organs or on the animal as a whole were observed. These results and earlier studies on (skin) cell substrate properties and physicochemical characteristics of the matrices indicate the suitability of the matrices as part of a cell‐seeded skin substitute. © 1994 John Wiley & Sons, Inc.
Ab initio studies of RO− … HOR′ complexes. Solvent effects on the relative acidities of water and methanol
Authors: Jorgensen William L. , Ibrahim Mustafa 
Published: December 2004

AbstractAb initio molecular orbital calculations are reported for complexes of hydroxide and methoxide anions with water and methanol. The basis set dependence of the results is carefully considered for HO− ⃛ H2O. 4‐31G and 6‐31G* calculations yield similar geometrical predictions; however, the 6‐31G* basis set is superior for computing dissociation energies. Further extension to the 6‐31G** level provides little change. The dissociation energies for the complexes range from 25 to 37 kcal/mole with hydroxide ion and methanol acting as the strongest base and acid. The difference in gas phase acidities of water and methanol is halved by the introduction of one solvent molecule.