bluuebunny/crossref_metadata_2025_split huggingface dataset:
HPLC–SPE–NMR in pharmaceutical development: capabilities and applications
Authors: Sandvoss Martin , Bardsley Ben , Beck Tony L. , Lee‐Smith Emma , North Stephanie E. , Moore Peter J. , Edwards Andrew J. , Smith Richard J. 
Published: July 2005

AbstractHigh‐performance liquid chromatography–solid phase extraction–NMR spectroscopy (HPLC–SPE–NMR) has recently become commercially available and has been evaluated with regard to its applicability in a pharmaceutical environment. The addition of an automated SPE unit to an HPLC–NMR system for peak trapping results in an improved NMR signal‐to‐noise ratio (S/N) and also has other practical advantages. The trapping efficiency is shown to depend on compound polarity and is highest for compounds eluting late on reversed‐phase HPLC systems. Multiple peak trapping further increases the S/N, again with the best results for less polar compounds. For polar compounds, multiple peak trapping resulted in no S/N gain as the amount of material retained on the SPE cartridge was equivalent to that from a single injection. When compared with conventional HPLC–NMR, a S/N gain of up to five‐fold could be achieved for some compounds in a single trapping step. A major advantage of the technique is the independence of the chromatographic step from the NMR step, resulting in greater versatility than conventional HPLC–NMR in the HPLC solvents and NMR solvents that can be used. Practical applications from both drug metabolite and drug impurity identification are presented. Copyright © 2005 John Wiley & Sons, Ltd.
Insights into cyclodextrin interactions during sample stacking using capillary isotachophoresis with on‐line microcoil NMR detection
Authors: Almeida Valentino K. , Larive Cynthia K. 
Published: July 2005

AbstractOn‐line capillary isotachophoresis (cITP)–NMR experiments were used to probe the interactions of the pharmaceutical compounds S‐alprenolol, S‐atenolol, R‐propranolol, R‐salbutamol and S‐terbutaline with β‐cyclodextrin (β‐CD) during cITP concentration. In cITP, ionic analytes are concentrated and separated on the basis of their electrophoretic mobility. Because neutral molecules have an electrophoretic mobility of zero, they are normally not concentrated or separated in electrophoretic experiments like cITP. Most of the analytes studied were concentrated by cITP sample stacking by a factor of around 300. For analytes that formed a strong inclusion complex, β‐CD co‐concentrated during cITP sample stacking. However, once the focusing process was complete, a discrete diffusional boundary formed between the cITP‐focused analyte band and the leading and trailing electrolyte, which restricted diffusion into and out of the analyte band. Copyright © 2005 John Wiley & Sons, Ltd.
Determination of regulatory phosphorylation sites in nanogram amounts of a synthetic fragment of ZAP‐70 using microprobe NMR and on‐line coupled capillary HPLC–NMR
Authors: Hentschel Petra , Krucker Manfred , Grynbaum Marc David , Putzbach Karsten , Bischoff Rainer , Albert Klaus 
Published: July 2005

AbstractThe protein kinase ZAP‐70 is involved in T‐cell activation and interacts with tyrosine‐phosphorylated peptide sequences known as immunoreceptor tyrosine activation motifs (ITAMs). We have studied the regulatory phosphorylation sites in the tryptic fragment containing amino acids 485–496 (ALGADDSYYTAR). The four possible peptides with phosphorylation at none, one, or both of the Y‐492 and Y‐493 tyrosines were specifically synthesized and analyzed by 1H/13C–NMR at 600 MHz using a capillary HPLC–NMR microprobe. Unambiguous discrimination of the peptides was possible via effect of chemical shifts of phosphorylation on the aromatic tyrosine protons. With the microprobe and the detection volume of 1.5 µl, it was possible to perform structure elucidation with the very small amounts available for the various peptides. For the syringe injection, 15 µg of the analyte were used (corresponding to ca 2 mg in classical 5‐mm tubes). Capillary HPLC–NMR spectra were recorded in the stopped‐flow mode from less than 400 ng of each peptide, using 1D and 2D techniques (1H,1H–COSY‐90, 1H/13C–HSQC, and 1H/13C–HMBC). Copyright © 2005 John Wiley & Sons, Ltd.
Identification of secondary metabolites from Streptomyces violaceoruber TÜ22 by means of on‐flow LC–NMR and LC–DAD–MS
Authors: Pham L. H. , Vater J. , Rotard W. , Mügge C. 
Published: July 2005

AbstractFor rapid screening of natural products from Actinomycetes, a combination of on‐line couplings LC–NMR, LC–DAD–MS and HPLC–PDA, as well as MALDI–TOF–MS is particularly suitable. Simultaneous use of these coupling techniques provides considerable advantages for the rapid identification of natural compounds in mixtures.The results of our present investigation on secondary metabolite products of Streptomyces violaceoruber TÜ 22 showed that more than 50% of the identified metabolites are new compounds. The structures of four new polyketides (granaticin C, metenaticin A, B and C) as well as four known ones (granaticin A, granatomycin E, daidzein and genistein) have been elucidated using LC–NMR, LC–MS/MS and –MSn techniques in combination with two‐dimensional NMR spectroscopy. Copyright © 2005 John Wiley & Sons, Ltd.
HPLC–NMR for tissue‐specific analysis of phenylphenalenone‐related compounds in Xiphidium caeruleum (Haemodoraceae)
Authors: Schneider Bernd , Paetz Christian , Hölscher Dirk , Opitz Stefan 
Published: July 2005

AbstractHPLC–1H NMR has been used to study the tissue‐specific distribution of phenylphenalenones, polyphenolic natural products of Xiphidium caeruleum, a neotropical member of the Haemodoraceae plant family. The present results provide insight into the occurrence of phenylphenalenone‐related compounds in root segments of whole plants and different in vitro culture lines of the same species. Copyright © 2005 John Wiley & Sons, Ltd.
Mouse zygotes with one diploid pronucleus formed as a result of ICSI can develop normally beyond birth
Authors: Krukowska Anna , Tarkowski Andrzej K. 
Published: July 2005

AbstractA mouse spermatozoon was injected into mouse secondary oocytes (ICSI) in the vicinity of the metaphase spindle. In 22% of oocytes injected successfully, the maternal chromatin (the haploid chromatids formed after the second meiotic division) and paternal chromatin (from the sperm nucleus) were surrounded by a common nuclear envelope to form one diploid bi‐parental pronucleus. However, the use of spermatozoa in which BrdU had been incorporated into DNA during spermatogenesis revealed, that maternal and paternal chromatin occupied two separate compartments within the one pronucleus. In the living state, the diploid pronucleus could be distinguished from a haploid one by its distinctly larger size and by a greater number of “nucleolus‐like bodies”—criteria confirmed karylogically at the 1st cleavage division. Such zygotes with one diploid pronucleus were able to develop in vitro into blastocysts as often as those with two haploid pronuclei [11/29 (38%) vs. 14/35 (40%)]. Seventy nine 2‐cell embryos developing in vitro from zygotes with one diploid pronucleus were transplanted to the oviducts of pseudopregnant recipients: two females had six foetuses when killed on the 17th day, and two females gave birth to nine young, eight of which survived and developed into normal fertile animals. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
Paratesticular metastasis from Wilms tumor associated with a hydrocele
Authors: Aydın G. Burça , Çiftçi Arbay Ö. , Yalçın Bilgehan , Akçören Zuhal , Çağlar Melda , Şenocak Mehmet E. , Büyükpamukçu Münevver 
Published: July 2005

AbstractMetastatic sites other than the lungs, lymph nodes, and liver are unusual for Wilms tumor (WT). Intra‐scrotal metastasis is very rare. We report a 3‐year‐old boy with stage IIA WT, who experienced paratesticular metastasis 2 months after surgery for an abdominal recurrence. He had right scrotal hydrocele at initial diagnosis. The patient underwent right radical orchiectomy, and pathological examination revealed paratesticular WT metastasis. Intra‐abdominal and peritoneal disseminated metastases followed. We considered that tumor cells spread through the patent processus vaginalis and grew at paratesticular space in hydrocele. One month after the end of 12 months of salvage chemotherapy and abdominal radiotherapy, the patient has no evidence of disease. © 2005 Wiley‐Liss, Inc.
Frequency independent‐dependent conductivity and dielectric properties of some ionomers
Authors: Yakuphanoglu Fahrettin , Erten Hilmi 
Published: July 2005

AbstractThe preparation and physical properties of some ionomers have been investigated. The addition of CH3I significantly improved the conductivity of the ionomers. At room temperature, the highest ionic conductivity value was found to be 4.93 10−8 S cm−1 in the I4 ionomer. The conductivity data do not obey the Arrhenius law and the non‐linearity indicates ionic transport. The alternating current conductivity parameters and dielectric constants of the ionomers were determined. Copyright © 2005 Society of Chemical Industry
An evaluation, comparison, and accurate benchmarking of several publicly available MS/MS search algorithms: Sensitivity and specificity analysis
Authors: Kapp Eugene A. , Schütz Frédéric , Connolly Lisa M. , Chakel John A. , Meza Jose E. , Miller Christine A. , Fenyo David , Eng Jimmy K. , Adkins Joshua N. , Omenn Gilbert S. , Simpson Richard J. 
Published: July 2005

AbstractMS/MS and associated database search algorithms are essential proteomic tools for identifying peptides. Due to their widespread use, it is now time to perform a systematic analysis of the various algorithms currently in use. Using blood specimens used in the HUPO Plasma Proteome Project, we have evaluated five search algorithms with respect to their sensitivity and specificity, and have also accurately benchmarked them based on specified false‐positive (FP) rates. Spectrum Mill and SEQUEST performed well in terms of sensitivity, but were inferior to MASCOT, X!Tandem, and Sonar in terms of specificity. Overall, MASCOT, a probabilistic search algorithm, correctly identified most peptides based on a specified FP rate. The rescoring algorithm, PeptideProphet, enhanced the overall performance of the SEQUEST algorithm, as well as provided predictable FP error rates. Ideally, score thresholds should be calculated for each peptide spectrum or minimally, derived from a reversed‐sequence search as demonstrated in this study based on a validated data set. The availability of open‐source search algorithms, such as X!Tandem, makes it feasible to further improve the validation process (manual or automatic) on the basis of “consensus scoring”, i.e., the use of multiple (at least two) search algorithms to reduce the number of FPs.∁
Synthesis of well‐defined polymers end‐functionalized with crosslinkable aziridine groups by living anionic polymerization
Authors: Kobayashi Mamoru , Uchino Kentaro , Ishizone Takashi 
Published: July 2005

AbstractWell‐defined end‐functionalized polystyrene, poly(α‐methylstyrene), and polyisoprene with polymerizable aziridine groups were synthesized by the termination reactions of the anionic living polymers of styrene, α‐methylstyrene, and isoprene with 1‐[2‐(4‐chlorobutoxy)ethyl]aziridine in tetrahydrofuran at −78 °C. The resulting polymers possessed the predicted molecular weights and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.1) as well as aziridine terminal moieties. The cationic ring‐opening polymerization of the ω‐monofunctionalized polystyrene having an aziridinyl group with Et3OBF4 gave the polymacromonomer, whereas the α,ω‐difunctional polystyrene underwent crosslinking reactions to afford an insoluble gel. Crosslinking products were similarly obtained by the reaction of the α,ω‐diaziridinyl polystyrene with poly(acrylic acid)‐co‐poly(butyl acrylate). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4126–4135, 2005
Polymerization of 1,2:5,6‐diepithio‐3,4‐di‐O‐methyl‐D‐mannitol, 1,2:5,6‐diepithio‐3,4‐di‐O‐methyl‐L‐iditol, and 1,2:5,6‐diepithio‐3,4‐di‐O‐methyl‐allitol using zinc complexes: The regio‐ and stereoselectivities and asymmetric synthesis of thiosugar polymers
Authors: Satoh Toshifumi , Imai Tomoko , Sugie Norihiko , Hashimoto Hisaho , Kakuchi Toyoji 
Published: July 2005

AbstractThe polymerizations of the diepisulfides 1,2:5,6‐diepithio‐3,4‐di‐O‐methyl‐D‐mannitol (1a), 1,2:5,6‐diepithio‐3,4‐di‐O‐methyl‐L‐iditol (1b), and 1,2:5,6‐diepithio‐3,4‐di‐O‐methyl‐allitol (1c) were carried out with ZnEt2/H2O, ZnEt2/alcohol, and ZnEt2/(S or R)‐1,1′‐bi‐2‐naphthol (BN) as the initiator systems. All the polymerizations proceeded without any gel formation and gave white, powdery products. The number‐average molecular weights of the obtained polymers were changed in the range of 5300–33,600. The polymerization of 1a using the ZnEt2/H2O (1/1) catalyst in tetrahydrofuran proceeded through a regio‐ and stereoselective cyclopolymerization mechanism to produce thiosugar polymers mainly consisting of 2,5‐anhydro‐1,5‐dithio‐D‐glucitol as the five‐membered ring units. The polymers obtained from 1b and 1c with ZnEt2/H2O exhibited lower stereoregularities than that from 1a. For the polymers obtained from 1a with the ZnEt2/alcohol systems, the molar fraction of the five‐membered ring units depended on the alcohol used as a ligand. On the other hand, the polymerization of 1c using ZnEt2/(R or S)‐BN asymmetrically proceeded, and optically active polymers consisting of desulfurized acyclic units were obtained. When ZnEt2/(R)‐BN (1/1) was used in toluene, the polymer with [α]D23 = +56.9° was obtained in an 88.6% yield. The resulting polymer had an isotactic‐rich structure consisting of about 90% (R)‐configurational units and about 10% (S)‐units. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4118–4125, 2005
Antimicrobial polymers containing melamine derivatives. II. Biocidal polymers derived from 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine
Authors: Chen Zhaobin , Sun Yuyu 
Published: July 2005

AbstractPoly(2‐vinyl‐4,6‐diamino‐1,3,5‐triazine) (PVDAT) and a series of poly(styrene‐co‐2‐vinyl‐4,6‐diamino‐1,3,5‐triazine) (PS‐co‐VDAT) copolymers were synthesized via conventional free‐radical polymerizations. The polymer structures were confirmed by Fourier transform infrared, NMR, and elemental analysis. The molecular weights were determined by gel permeation chromatography studies, and the thermal properties were characterized by differential scanning calorimetry and thermogravimetric analysis. After treatment with chlorine bleach, PVDAT and PS‐co‐VDAT provided potent antimicrobial functions against multidrug‐resistant Gram‐negative and Gram‐positive bacteria. The antimicrobial functions were durable for longer than 3 months and rechargeable for more than 50 times. The structure–property relationship of the polymers was further discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4089–4098, 2005
Densely grafting copolymers of ethyl cellulose through atom transfer radical polymerization
Authors: Shen Dawa , Yu Hui , Huang Yong 
Published: July 2005

AbstractDensely grafting copolymers of ethyl cellulose with polystyrene and poly(methyl methacrylate) were synthesized through atom transfer radical polymerization (ATRP). First, the residual hydroxyl groups on the ethyl cellulose reacted with 2‐bromoisobutyrylbromide to yield 2‐bromoisobutyryloxy groups, known to be an efficient initiator for ATRP. Subsequently, the functional ethyl cellulose was used as a macroinitiator in the ATRP of methyl methacrylate and styrene in toluene in conjunction with CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalyst system. The molecular weight of the graft copolymers increased without any trace of the macroinitiator, and the polydispersity was narrow. The molecular weight of the side chains increased with the monomer conversion. A kinetic study indicated that the polymerization was first‐order. The morphology of the densely grafted copolymer in solution was characterized through laser light scattering. The individual densely grafted copolymer molecules were observed through atomic force microscopy, which confirmed the synthesis of the densely grafted copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4099–4108, 2005
Self‐heating and conduction of an acetylene carbon black filled high‐density polyethylene composite at the electric–thermal equilibrium state
Authors: Song Yihu , Zheng Qiang 
Published: July 2005

AbstractThe electric self‐heating and conduction behaviors of a high‐density polyethylene/carbon black composite at the electric–thermal equilibrium state are studied. An equation describing the current density/electric‐field strength (J–E) characteristic is derived on the basis of an equation proposed for the self‐heating temperature as a function of the field strength. The conduction is related to the electronic tunneling and the resistor breakdown due to self‐heating that dominate the nonlinear J–E characteristic below and above a critical field strength corresponding to the J maximum, respectively. The influences of the initial structure of the percolation network and the physical state of the matrix on the conduction are also discussed on the basis of scaling arguments of the self‐heating and the nonlinear J–E characteristic with respect to the initial resistivity at various ambient temperatures from 19 to 120 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2484–2492, 2005
Composition dependence of ordered structures in mixed micellar aqueous solutions of hydrophobically modified poly(ethylene glycol)s
Authors: Iizuka Kenichi , Numasawa Naoko , Hiraoka Kazuyuki , Yamazaki Ritsuko , Nose Takuhei 
Published: July 2005

AbstractOrdered structures of micellar aqueous solutions of poly(ethylene glycol) (PEG) monododecylether mixtures [octaethylene glycol monododecylether (C12E8) and poly(ethylene glycol) monododecylether (C12E25)] have been investigated as a function of the C12E8/C12E25 composition by means of X‐ray scattering. C12E8 and C12E25 have different chain lengths of corona PEG, that is, 8 and 25 repeating units, respectively. The following results have been obtained. First, in the C12E8‐rich and C12E25‐rich regions, the mixtures take hexagonal and cubic phases, respectively. The hexagonal phase remains over a wider range of compositions and is more stable for the mixing of the other component than the cubic phase. Second, in the C12E8‐rich region of the cylindrical hexagonal packing, the nearest‐neighbor micellar distance increases, whereas the association number density remains constant, with an increasing amount of mixed C12E25 possessing longer corona chains. Third, in contrast to this, the nearest‐neighbor micellar distance of the body‐centered cubic packing exhibits almost no change, whereas the association number increases as C12E8 of shorter corona chains is increasingly incorporated. Fourth, self‐consistent field calculations reasonably reproduce the experimental findings of the second and third observations. We discuss the phase stability and the structural changes with the composition in terms of differences in the PEG corona‐chain length. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2474–2483, 2005
Exhaustive Metropolis Monte Carlo sampling and analysis of polyalanine conformations adopted under the influence of hydrogen bonds
Authors: Podtelezhnikov Alexei A. , Wild David L. 
Published: July 2005

AbstractWe propose a novel Metropolis Monte Carlo procedure for protein modeling and analyze the influence of hydrogen bonding on the distribution of polyalanine conformations. We use an atomistic model of the polyalanine chain with rigid and planar polypeptide bonds, and elastic α carbon valence geometry. We adopt a simplified energy function in which only hard‐sphere repulsion and hydrogen bonding interactions between the atoms are considered. Our Metropolis Monte Carlo procedure utilizes local crankshaft moves and is combined with parallel tempering to exhaustively sample the conformations of 16‐mer polyalanine. We confirm that Flory's isolated‐pair hypothesis (the steric independence between the dihedral angles of individual amino acids) does not hold true in long polypeptide chains. In addition to 310‐ and α‐helices, we identify a kink stabilized by 2 hydrogen bonds with a shared acceptor as a common structural motif. Varying the strength of hydrogen bonds, we induce the helix–coil transition in the model polypeptide chain. We compare the propensities for various hydrogen bonding patterns and determine the degree of cooperativity of hydrogen bond formation in terms of the Hill coefficient. The observed helix–coil transition is also quantified according to Zimm–Bragg theory. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Topology optimization of slightly compressible fluids
Authors: Evgrafov A. 
Published: July 2005

AbstractWe consider the problem of optimal design of flow domains for Navier–Stokes flows in order to minimize a given performance functional. We attack the problem using topology optimization techniques, or control in coefficients, which are widely known in structural optimization of solid structures for their flexibility, generality, and yet ease of use and integration with existing FEM software. Topology optimization rapidly finds its way into other areas of optimal design, yet until recently it has not been applied to problems in fluid mechanics. The success of topology optimization methods for the minimal drag design of domains for Stokes fluids (see the study of Borrvall and Petersson [12]) has lead to attempts to use the same optimization model for designing domains for incompressible Navier–Stokes flows. We show that the optimal control problem obtained as a result of such a straightforward generalization is ill‐posed, at least if attacked by the direct method of calculus of variations. We illustrate the two key difficulties with simple numerical examples and propose changes in the optimization model that allow us to overcome these difficulties. Namely, to deal with impenetrable inner walls that may appear in the flow domain we slightly relax the incompressibility constraint as typically done in penalty methods for solving the incompressible Navier–Stokes equations. In addition, to prevent discontinuous changes in the flow due to very small impenetrable parts of the domain that may disappear, we consider so‐called filtered designs, that has become a “classic” tool in the topology optimization toolbox. Technically, however, our use of filters differs significantly from their use in the structural optimization problems in solid mechanics, owing to the very unlike design parametrizations in the two models. We rigorously establish the well‐posedness of the proposed model and then discuss related computational issues.
A numerical study on the suppression of draw resonance by inertia
Authors: Hagen T. , Langwallner B. 
Published: July 2005

AbstractWe study the one‐dimensional equations governing the formation of viscous fluid fibers in forced elongation when inertia enters the dominant balance. Even though it has been known for a long time that quite weak inertial forces suffice to suppress the onset of draw resonance, we shall give quantitatively more precise results than those reported before in the context of linear stability analysis. In addition, we shall demonstrate by numerical simulation that these findings remain valid in the nonlinear regime.