bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isoelectric focusing in long immobilized pH gradient gels to improve protein separation in proteomic analysis
Authors: Poland Julia , Cahill Michael A. , Sinha Pranav 
Published: April 2003

AbstractThe number of protein spots detected on two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE) gels increases as the gel size increases. The largest commercially available systems resolve a few thousand spots, being only a fraction of the total proteome. We have developed an extremely long isoelectric focusing (IEF) system aimed at more complete protein profiling. The system is especially well suited to sensitive detection methods, such as radioactive detection. The major constraint preventing progress in this area has been the inability to create an even density gradient during the immobilized pH gradient (IPG) casting process. We demonstrate for the first time that this constraint can be effectively overcome, to enable greatly increased IEF separating power with all the advantages of IPG technology,
Spotting and quantification of phosphoproteins purified by gel electrophoresis and laser ablation‐element mass spectrometry with phosphorus‐31 detection
Authors: Wind Mathias , Feldmann Ingo , Jakubowski Norbert , Lehmann Wolf D. 
Published: April 2003

AbstractLaser ablation inductively coupled plasma‐mass spectrometry (ICP‐MS) with 31P detection has been used for spotting of phosphoproteins after one‐dimensional polyacrylamide gel electrophoresis (1‐D PAGE) and membrane transfer. By analyzing a mixture of myoglobin, α‐casein and reduced fibrinogen it is demonstrated that phosphoproteins are specifically recognized by this method. A special washing step was found to be necessary to remove phosphate noncovalently bound to proteins. The 31P signal was found to contain quantitative information both with respect to relative and absolute amounts of phosphorus present in phosphoproteins. Normalizing the 31P signal from a single laser ablation trace by the total amount of phosphoprotein applied to the gel, a detection limit of 5 pmol of phosphorus is estimated.
Assessing matrix assisted laser desorption/ ionization‐time of flight‐mass spectrometry as a means of rapid embryo protein identification in rice
Authors: Fukuda Masafumi , Islam Nazrul , Woo Sun‐Hee , Yamagishi Azumi , Takaoka Motoko , Hirano Hisashi 
Published: April 2003

AbstractRice embryo proteins were separated by two‐dimensional gel electrophoresis (2‐DE). A total of 105 spots were digested with trypsin and the resultant peptides were analyzed by matrix assisted laser desorption/ionization‐time of flight‐mass spectrometry (MALDI‐TOF‐MS). Raw mass spectra were fully‐automatically processed and searched with selected monoisotopic masses against SWISS‐PROT/TrEMBL and NCBInr databases. High quality mass spectra were obtained from 53 spots, of which 36 spots were identified including 29 not registered in databases. Fifty percent of the rice embryo proteins resolved in 2‐DE could not be identified, indicating more efficient sample preparation techniques need to be developed in the future. At least four to five matching peptides were found to be essential for unambiguous identification of rice embryo proteins; peptide matching of less than four lead to ambiguous results. The suitability of peptide mass fingerprinting method as a means of rapid embryo protein identification in rice was discussed.
Geoarchaeological insights gained from surficial geologic mapping, middle Moche Valley, Peru
Authors: Huckleberry Gary , Billman Brian R. 
Published: April 2003

AbstractWe present the results of detailed surficial geologic mapping for a 10 km2 area of alluvial (quebrada) deposits located in the middle Moche Valley of Peru, where archaeological features and deposits provide cross‐cutting relationships and numerical age control for late Holocene erosion and deposition associated with El Niño. Despite surfaces containing clasts that are heavily pitted and cracked due to salt weathering, archaeological and 14C dates indicate that most quebrada landforms in the study area are late Holocene in age and may reflect enhanced alluviation associated with increased El Niño activity beginning ca. 6000 cal yr B.P. Our study provides criteria for correlative dating of other Holocene landforms in the Moche Valley area but urges caution in long‐distance (>100 km) correlation because of geographic variability in surface weathering. Surficial geologic mapping aided by archaeological age control allows improved understanding of the rates of landscape change important to the development of complex irrigation‐based societies in the Peruvian Desert. © 2003 Wiley Periodicals, Inc.
Paleolithic burnt bone horizons from the Swabian Jura: Distinguishing between in situ fireplaces and dumping areas
Authors: Schiegl Solveig , Goldberg Paul , Pfretzschner Hans‐Ulrich , Conard Nicholas J. 
Published: April 2003

AbstractHohle Fels Cave is one of several Upper Paleolithic sites on the eastern extension of the Swabian Alb in southwestern Germany. Several phases of excavations have been conducted since 1870. The archaeological inventories comprise a broad range of artifacts produced from stone, bone, teeth, ivory, and antler. The site has also yielded Paleolithic rock art, sculpture, and engravings. The Pleistocene inventories unearthed so far belong to the Magdalenian, Gravettian, and Aurignacian; Middle Paleolithic horizons may well be uncovered as excavations continue. The chronology of three main occupation phases has been established with numerous 14C measurements. The Magdalenian dates to about 13,000 yr B.P., and the richest Gravettian deposit contains a burnt bone‐layer extending over ca. 12 m2 that dates to about 29,000 yr B.P. The underlying Aurignacian horizons predate 30,000 yr B.P. The Gravettian burnt bone layer (archaeological layer IIcf) is a key horizon because of its distinct composition and color and its large horizontal extension. Layer IIcf has been examined using a combination of analytical techniques including micromorphological analysis of thin sections with polarizing light microscopy and scanning electron microscopy for fabric and identification of mineral and biogenic constituents. The bone mineral composition was analyzed by Fourier transform infrared spectroscopy (FTIR) and electron probe microanalytical techniques. These investigations in tandem with the field observations indicate intense burning of bones as fuel. The micromorphological and contextual archaeological data suggest that layer IIcf is a secondary dump rather than an in situ accumulation. This deposit and other Paleolithic burnt deposits in the Swabian Jura appear to reflect intense periods of winter occupation in these caves. © 2003 Wiley Periodicals, Inc.
Intra‐ and extracellular macromolecular networks: physics and biological function
Authors: Sackmann Erich 
Published: April 2003

AbstractIn order to adapt the physical properties of living materials to their biological function, nature has developed (polyelectrolytic) polymers with outstanding physical behaviour. Nature provides giant macromolecules (such as actin filaments), which can be directly observed and which comprise the whole range of flexibilities from the random coil to the rigid rod. The structure and dynamics of the macromolecules and networks can be manipulated in many ways by making use of the tricks of nature. In the present contribution some of the most pertinent elements of the intracellular and extracellular matrix are introduced. One main purpose of this contribution is to show that many of these polymers are also of great potential interest in polymer science, in order to study fundamental properties of macromolecules and macromolecular networks. Another intention is to bridge the gap between biological material research and the physics and chemistry of polymers and other complex fluids and to plead for a closer cooperation between the two fascinating worlds.
Engineering plastics from lignin, 23. Network formation of lignin‐based epoxy resins
Authors: Hofmann Klaus , Glasser Wolfgang 
Published: April 2003

AbstractThe network‐forming behavior, gelation, and vitrification of lignin‐polyether‐copolymer‐epoxide/amine resins were determined using a recently described dynamic mechanical thermal analysis (DMTA)‐based method. Six resins were studied which differed in lignin content, polyether arm length, and molecular weight. Glass transition temperature (Tg)‐cure time master curves could be constructed for cure temperatures ranging from 90 to 200°C; and semiexperimental vitrification plots were derived for each system based on the knowledge of activation energy and cure time at a reference temperature. The point at which the cure process becomes diffusion‐controlled (i.e., vitrification) happens at lower extents of conversion for lignin‐rich fractions. Near vitrification, the cure events change from n‐th‐ to second‐order kinetics, and this indicates a reduction in polyether‐arm mobility. This suggests that the crosslinking of lignin centers with polyether arms produces a network in which the reactant‐carrying flexible arms do not have sufficient free volume to react. The greatest increase in Tg during crosslinking is about 100°C for all molecular weight fractions, and this suggests that high‐Tg networks can only be achieved with high‐Tg prepolymers.
Conformational stability and force field of polyphosphazenes: MNDO calculations, vibrational spectra and normal coordinate analyses of [NP(R)2]n (R = Cl, OCH2CF3, OC6H5)
Authors: Bougeard Daniel , Brémard Claude , De Jaeger Roger , Lemmouchi Yahia 
Published: April 2003

AbstractRaman and Fourier‐transform Raman spectra (1500 − 100 cm−1) of (PCl2N)n (PDCP) were recorded in the solid phase and in solution at room temperature. Raman (3 500 − 100 cm−1) and infrared (4 000 − 200 cm−1) spectra of [P(OCH2CF3)2N]n (PDFP) and [P(OC6H5)2N]n (PDPP) were recorded in the solid phase and at different temperatures (in the case of Raman spectroscopy). The conformation of the isolated macromolecule PDCP is assumed to be analogous to the geometry of the Cl2(O)PN(PCl2N)6PCl3 oligomer optimized by the use of MNDO (modified neglect of diatomic overlap) calculations. The optimized cis‐trans conformation is in good agreement with the X‐ray experimental data concerning the polymer. The calculated low energy barriers around the PN bond along the chain axis can explain the flexibility of the phosphazene backbone and the elastomeric properties of the polymers. The MNDO calculation of the harmonic force field of Cl2(O)PN(PCl2N)6PCl3 is in reasonable agreement with the experimental values for (PCl2N)n in solution as well as in the amorphous phase. The normal coordinate analyses of (PCl2N)n were undertaken according to several structural hypotheses using a force field derived from linear short‐chain molecules. The Raman spectra of PDCP in solution or in the amorphous phase are in reasonable agreement with the vibrational frequencies calculated for a planar cis‐trans macromolecule and have a striking resemblance with those of linear short‐chain analogs Cl2(O)PN(PCl2N)n PCl3 (n = 1,2). The Raman and infrared spectra of the substituted polymers PDFP and PDPP are dominated by the characteristic features of the chain substituents.
Etude de la réaction de télomérisation d'un monomère tensioactif cationique
Authors: Boutevin Bernard , Robin Jean‐Jacques , Boyer Bernard , Roque Jean‐Pierre , Senhaji Omar 
Published: April 2003

AbstractA polymerizable methacrylic surfactant is synthetized from methacryloyl chloride and 11‐bromoundecanol. The obtained cationic monomer is telomerized with a fluorinated thiol, and the transfer constant CT is calculated. This value is in the same range as transfer constants of classical methacrylic monomers. The obtained kp2/kT is low because of the long chain ester. Polymers were prepared in homogeneous solution with an average molecular weight of 25 000.
Synthesis of chiral and racemic functional polymers from glycidol and thioglycidol
Authors: Taton Daniel , Le Borgne Alain , Sepulchre Maurice , Spassky Nicolas 
Published: April 2003

AbstractRacemic and optically active protected glycidols (as 1‐ethoxyethyl ethers) are readily polymerized with anionic initiators (e.g., CsOH). Polymers with molecular weights up to 30 000 are obtained without cleavage of the protective group. Oligomers (degree of polymerization [DPn] 5 to 10) are prepared using an aluminium complex derived from a Schiff's base. The protected thioglycidol (synthesized from the protected glycidol) leads to very high‐molecular‐weight polymers (150 000–320 000) using anionic or anionic coordinated initiators. Copolymers of protected glycidol with ethylene oxide are obtained with KOH as initiator. Regeneration of hydroxyl groups in polymers is carried out with acidic cleavage. Treatment of protected polyglycidol with formic acid leads first to the formate of polyglycidol. Then, after saponification, pure polyglycidol is obtained. The use of aqueous hydrochloric acid leads directly to the free polymer.
End‐group modification of α‐hydro‐ω‐methoxypoly(oxyethylene), 3. Facile methods for the introduction of a thiol‐selective reactive end‐group
Authors: Herman Sabine , Loccufier Johan , Schacht Etienne 
Published: April 2003

AbstractThree methods for the introduction of a thiol‐selective reactive end‐group into α‐hydro‐ω‐methoxypoly(oxyethylene) are described and evaluated. In a first method, α‐amino‐ω‐methoxypoly(oxyethylene) was reacted with succinimido 3‐(2‐pyridyldithio)propionate (SPDP). In a second approach, the hydroxyl end‐group of α‐hydro‐ω‐methoxypoly(oxyethylene) was activated with 4‐nitrophenyl chloroformate, and subsequently reacted with 2‐tritylthioethylamine. Conversion of the trityl thioether into an aromatic disulfide with 2‐nitrophenylsulfenyl chloride yielded a polymer with a thiol‐specific reactive disulfide end‐group. However, it was shown that dismutation in buffer medium does occur, what makes this approach less attractive. A third method involved the conversion of the trityl thioether into a sulfenyl thiocarbonate by reaction with an alkoxycarbonylsulfenyl chloride. Both the SPDP‐modified and the alkoxycarbonyl disulfide‐modified poly(oxyethylene) were found to be suitable thiol‐specific reactive polymers for protein modification. This was demonstrated in a model reaction using reduced glutathione as a thiol‐carrying peptide.
Studies on the polymerization of ethylene using a high‐yield MgCl2‐supported titanium catalyst, 3. Chemical composition of the standard system and its alterations
Authors: Fuhrmann Hans , Strübing Brigitte 
Published: April 2003

AbstractMiddle‐range n‐alkyl chlorides are the most suitable components among a variety of tested alkyl halides in the preparation process of the highly active Ti‐Mg catalyst MTKST. A material balance of the initial components RCl, THF and CCl4 revealed the formation of oligomers, chloro‐containing telomers and poly‐THF apart from low‐molecular side products. The former are important modifiers of the suspension catalyst and exert a positive influence on catalyst activity and polymer properties, as was shown in the polymerization of ethylene. Schlenk equilibrium and extent of Wurtz type coupling in the Grignard synthesis step, which have been evaluated by titration of RMg bonds and Cl analysis of both the liquid and solid phase of the catalyst, predetermine the quality of the catalyst being formed.
Side‐chain liquid‐crystalline polymers containing siloxane spacer, 3. Thermal properties of copolymers containing different types of mesogens
Authors: Nagase Yu , Saito Takanori , Abe Hirokazu , Takamura Yuriko 
Published: April 2003

AbstractCopolymerization of monomers containing the disiloxane unit in the spacer component and linear triple‐core mesogens with comonomers containing linear double‐core mesogens, or laterally attached triple‐core mesogens was carried out radically. The effect of copolymer composition and monomer structure on the mesomorphic properties of the obtained copolymers was investigated in detail. The copolymers with a comonomer content up to 50 mol‐%, exhibit an enantiotropic nematic phase, whereas the parent homopolymers containing triple‐core mesogens exhibit a smectic phase. The copolymer containing more than 50 mol‐% of the comonomer shows no mesophase. The isotropization temperature of the copolymers decreases with increasing comonomer content. However, the glass transition temperature is almost unchanged upon introduction of the comonomer unit. In case of copolymers containing laterally attached mesogens, a smectic phase was observed below the temperature range of the nematic phase. Consequently, the mesophase and the temperature range of the liquid‐crystalline state can be controlled by the introduction of the comonomer unit whose parent homopolymer does not exhibit any mesophase.
Liquid‐crystalline epoxy resins: a glycidyl‐terminated benzaldehyde azine cured in the nematic phase
Authors: Carfagna Cosimo , Amendola Eugenio , Giamberini Marta , Filippov Andrei G. 
Published: April 2003

AbstractA novel glycidyl‐terminated benzaldehyde azine was synthesized and subsequently cured with an aromatic diamine. The resulting liquid‐crystalline network was characterized by means of optical microscopy, X‐ray analysis and dynamic‐mechanical analysis. The influence of the curing temperature on the nematic textures is pointed out. The curing reaction was followed by means of differential scanning calorimetry and dielectric analysis.
Palladium‐catalyzed synthesis of poly(p‐phenyleneethynylene)s
Authors: Solomin Victor A. , Heitz Walter 
Published: April 2003

AbstractPoly(p‐phenyleneethynylene)s were obtained by reacting 1,4‐dihaloarenes with 2‐methyl‐3‐butyn‐2‐ol in a two‐step one‐pot process. In the first step a dihaloarene is reacted with two equivalents of 2‐methyl‐3‐butyn‐2‐ol at room temperature in the presence of an aqueous base. For polycondensation a second equivalent of dihaloarene is added and reacted at 100°C. Soluble polymers with M̄w of 1–2 · 104 were obtained. They show blue fluorescence.
Détermination des masses et des distributions moléculaires d'un poly(aryléthercétone‐co‐sulfone) semi‐cristallin (HTX) à l'aide d'une méthode de dérivatisation chimique, 1. Caractérisation moléculaire du HTX en solution dans l'acide sulfurique concentre
Authors: Daoust Daniel , Devaux Jacques , Godard Pierre , Strazielle Claude 
Published: April 2003

AbstractHTX, a poly(aryletherketone‐co‐sulfone), is characterized in solution in concentrated sulfuric acid. Upon dissolution in concentrated H2SO4, HTX is chemically modified by sulfonation of phenyl rings. The modification of the chemical structure is studied with a model compound by means of IR spectroscopy. The increase of the molar mass corresponding to a complete sulfonation is determined by means of mass spectrometry. Light scattering and 19F NMR measurements are performed in order to obtain the weight‐ (M̄w)s and number‐average (M̄n)s molar masses of sulfonated HTX samples. (M̄w)s values allow the determination of the Mark‐Houwink‐Sakurada relationship for HTX in 99,5% H2SO4 at 25°C.
New crown ether resins prepared by cationic template polymerization
Authors: Li Kai , Ferrari Lorenzo P. , Brown Chris , Stöuver Harald D. H. 
Published: April 2003

AbstractThe synthesis of several dibenzo‐18‐crown‐6 derivatives, and their acid catalyzed incorporation into crosslinked styrene and 4‐methoxystyrene based copolymers is described. Some of these reactions were carried out in the presence of chiral ammonium cations acting as non‐covalent templates. The polymers have been characterized by IR, and by 1H and 13C solution state and magic angle spinning NMR.
Interaction of crosslinked poly(4‐vinylpyridine) with methyl orange
Authors: Kim Woo‐Sik , Lee Suk‐Kee , Seo Kwan‐Ho 
Published: April 2003

AbstractVarious crosslinked poly(4‐vinylpyridine)s (3) having different degrees of crosslinking were prepared by the radical copolymerization of 4‐vinylpyridine (1) with N,N′‐hexamethylenediacrylamide (2) as a crosslinker. These crosslinked polymers were examined for their ability to bind methyl orange at various temperatures in a buffer solution of pH 7. The first binding constants (K1) and thermodynamic parameters that accompany the binding were evaluated. The values of K1 show bell‐shaped curves against both the binding temperature and the degree of crosslinking of 3. Lower temperature and higher degree of crosslinking for the maximum binding in the bell‐shaped phenomenon of this binding system were observed, when they were compared with those of the previously reported binding systems, 1/N,N′‐methylenediacrylamide copolymers‐methyl orange and 1/N,N′‐tetramethylenediacrylamide copolymers‐methyl orange. The values of enthalpy change and entropy change increase with increasing degree of crosslinking of 3, whereas the absolute magnitude of free energy change is not increased. These results could be accounted for in terms of the temperature dependence of the hole size of 3 rather than the hydrophobic interaction in the binding process.
Thermally crosslinked rigid…rod aramids, 1. Synthesis of a new monomer and its polymerization
Authors: Rickert Christoph , Neuenschwander Peter , Suter Ulrich W. 
Published: April 2003

AbstractWith 2,2,6,6‐tetraoxo‐1,3,5,7‐tetrahydro‐2,6‐dithia‐s‐indacene‐4,8‐diamine (DSDA) (8), a new monomer for the synthesis of thermally crosslinkable rigid‐rod aramids was developed. DSDA was copolymerized with p‐phenylenediamine and terephthaloyl dichloride by a low‐temperature solution polycondensation to give high‐molecular‐weight aramids (inherent viscosity ηinh > 2,2 dL/g). The fraction of DSDA could be varied from 0 to 100 mol‐% of the diamine used in the condensation. All polymers showed a weight loss due to thermal elimination of SO2. Thermal crosslinking could be effected by curing the samples at high temperatures (280–320°C). The crosslinking reaction was investigated by means of thermogravimetry (TG), thermogravimetry/mass spectrometry (TG‐MS), Fourier transform infrared (FT‐IR), 13C cross polarization‐magic angle spinning nuclear magnetic resonance (13C CP‐MAS NMR) and electron paramagnetic resonance (EPR). The activation energy for this reaction was found to be between 150 and 170 kJ/mol. Curing of the polymer samples led to the generation of stable, matrix‐isolated radicals.
Structural study of compounds modelling elementary polymer units, 6. X‐ray structural and quantum‐chemical investigation of the cis‐ and trans‐isomeric models of the polynaphthoylenebenzimidazole elementary units
Authors: Lindeman Sergey V. , Ponomaryov Igor I. , Raevsky Nikolai I. , Struchkov Yurii T. , Rusanov Alexandr L. 
Published: April 2003

AbstractThe X‐ray structural investigation of the naphthoylenebis‐(benzimidazole) (1) cis‐ and trans‐isomers as models for the cis and trans elementary units of the corresponding poly(naphthoylene‐benzimidazoles) (PNBI) was carried out. The correctness of the previous identification of the isomers was confirmed, and exact geometrical parameters of the PNBI elementary units (required, in particular, for the calculation of the Kuhn segment of PNBI) were determined. Quantum‐chemical semi‐empirical calculations of the ground and excited electronic states of the isomers were carried out. Both experimental and theoretical data confirm a larger stability of the planar π‐conjugated structure of the trans‐isomer in comparison with the cis‐isomer in the ground as well as in the excited electronic state. Crystals of the cis‐ and trans‐isomers obtained from trifluoroacetic acid solutions are the solvates of bis(trifluoroacetates) of diprotonated 1 with an extremely high content of the solvating trifluoroacetic acid. This peculiarity is favourable for modelling the main characteristics of the interaction between PNBI and protonic polar solvent molecules, viz. preferred types of H‐bonding and a possibility of interaction of the electronic lone pairs of the solvent molecules with the π‐electronic systems of the elementary units of PNBI by charge transfer complexes.