bluuebunny/crossref_metadata_2025_split huggingface dataset:
Collision‐induced fragmentations of the (M‐H)− parent anions of underivatized peptides: An aid to structure determination and some unusual negative ion cleavages
Authors: Bowie John H. , Brinkworth Craig S. , Dua Suresh 
Published: October 2002

Abstract

I.
Introduction
87

II.
Discussion
88

A. The Backbone Cleavages of (M‐H)− Parent Anions of Peptides
88

1.  α‐ and β‐Backbone Cleavages
89

2.  The β′ Cleavage
92

3.  The Asp and Asn γ and δ Backbone Cleavages (Also Phe, Tyr, His, and Trp)
94

4.  The δ‐ and γ‐Cleavages of Glu and Gln
96

5.  Ser and Thr Cleavages: Side Chain and Backbone Fragmentations
99

a.  The side chain cleavages
99

b.  The backbone cleavage reactions of Ser and Thr
100

6.  Other Backbone Cleavage Processes
102

Acknowledgments
105

References
105

This article describes the fundamental cleavage reactions of (M‐H)− anions of underivatized peptides that contain up to 25 amino acid residues. The experimental observations of these cleavages have been backed up by molecular modeling, generally at the AM1 level of theory. The basic cleavages are the ubiquitous α‐ and β‐backbone cleavage reactions, which provide information similar to that of the B and Y + 2 cleavages of MH+ ions of peptides. The residues Asp and Asn also effect cleavages of the backbone (called δ‐ and γ‐cleavages), by reactions initiated from side chain enolate anions, causing elimination reactions that cleave the backbone between the Asp (Asn) NC backbone bond. Glu and Gln also direct analogous δ‐ and γ‐cleavages of the backbone, but in this case the processes are initiated by attack of the side chain CO2− (CONH−) to form a lactone (lactam). Ser and Thr residues undergo characteristic fragmentations of the side chain. These processes, losses of CH2O (Ser) and MeCHO (Thr), convert these residues into Gly. In larger peptides, Ser and Thr can effect two backbone cleavage reactions, called γ‐ and ε‐processes. The C‐terminal CO2− (or CONH−) forms a hydrogen bond with the side chain OH (of Ser or Thr), placing the C‐terminal residue in a position where it may affect SN2 attack at the electrophilic backbone CH of Ser, with concomitant cleavage of the backbone. All of the above negative ion cleavages require the peptide backbone to be conformationally flexible. However, there is a backbone cleavage that requires the peptide to have an alpha‐helical conformation in order for the two reacting centers to approach. This cleavage is illustrated for the Glu23‐initiated backbone cleavage at Ile21 for the (M‐H)− anion of the antimicrobial peptide caerin 1.1. © 2002 Wiley Periodicals, Inc., Mass Spec Rev 21:87–107, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mas.10022
Design and synthesis of sialyl Lewisx mimics as E‐ and P‐selectin inhibitors
Authors: Kaila Neelu , Thomas IV Bert E. 
Published: October 2002

AbstractThe selectins are a family of cell‐adhesion proteins that mediate the rolling of leukocytes on activated endothelial cells through the recognition of the carbohydrate epitope sialyl Lewisx (sLex). Control of the leukocyte‐endothelial cell adhesion process may prove useful in cases where excess recruitment of leukocytes can contribute to acute diseases such as stroke and reperfusion injury and chronic diseases such as psoriasis and rheumatoid arthritis. The development of molecules that block the interactions between sLex and the selectins has become an active area of research. In this review, we will highlight the various approaches taken toward the development of sLex mimetics as antagonists of E‐ and P‐selectin, including the use of structural information about the selectins and their interactions with sLex that have been revealed through the use of NMR, protein crystallography and molecular modeling. © 2002 Wiley Periodicals, Inc. Med Res Rev, 22, No. 6, 566–601, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/med.10018
Existence of multiple positive solutions for −Δu−μ(u/∣x∣2)=u2*−1+σf(x)
Authors: Cheng Ting , Zhao Charles Xuejin 
Published: October 2002

AbstractIn this paper, we consider the semilinear elliptic problem

where Ω⊂ℝN (N⩾3) is a bounded smooth domain such that 0∈Ω, σ>0 is a real parameter, $$\mu < \overline{\mu } = (N - 2)^{2} /4$$ and f(x) is some given function in L∞(Ω) such that f(x)⩾0, f(x)≢0 in Ω. Some existence results of multiple solutions have been obtained by implicit function theorem, monotone iteration method and Mountain Pass Lemma. Copyright © 2002 John Wiley & Sons, Ltd.
Microstrip antenna controlled by p‐i‐n diodes: Influence of the bias current on the antenna efficiency
Authors: Laheurte J. M. , Tosi H. , Dubard J. L. 
Published: October 2002

AbstractThis Letter points out the drop in radiation efficiency observed in active microstrip antennas with switching capabilities for inadequate values of the bias current. For a frequency agile antenna based on p‐i‐n diodes, a trade‐off between the dc consumption of the diodes and the antenna gain is demonstrated. It is also shown that this type of integrated active antenna can be reasonably predicted by a simple resistor model of the diode in a TLM analysis. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 44–47, 2002; DOI 10.1002/mop.10226
TACC3 expression and localization in the murine egg and ovary
Authors: Hao Zhonglin , Stoler Mark H. , Sen Buer , Shore Amy , Westbrook Anne , Flickinger Charles J. , Herr John C. , Coonrod Scott A. 
Published: October 2002

AbstractA protein spot cored from a silver‐stained two dimensional (2D) gel of germinal vesicle stage immature mouse oocytes was identified as Transforming Acidic Coiled Coil containing protein (TACC3) by tandem mass spectrometry. PCR amplification revealed two alternatively spliced forms, Tacc3a and Tacc3b, in mouse ovarian cDNA libraries. TACC3a encoded a 630 aa protein with a predicted mass of 70 kDa. It contained seven 24 aa repeats at the N‐terminus and two coiled‐coil domains at the C‐terminus. TACC3b encoded a 426 aa protein with a predicted mass of 49 kDa also containing two coiled coil domains, but lacking the 168 aa repeat region. In addition to homology to the TACC family members, murine TACC3 also showed 35.7% identity to the Xenopus protein, Maskin, a cytoplasmic polyadenylation element binding protein (CPEB)‐associated factor. Northern blot analysis demonstrated that TACC3a is abundantly expressed in adult testis and spleen and is moderately expressed in the ovary, heart, and lung, suggesting a wide tissue distribution. Both myc‐tagged TACC3a and TACC3b targeted to the cytoplasm of transiently transfected CV‐1 cells. In situ hybridization of mouse ovarian tissue sections displayed abundant expression of TACC3 specifically in the cytoplasm of growing oocytes, but not in primordial or atretic follicles. This pattern of expression suggests that TACC3 is expressed in ovarian cells undergoing active growth and development. Mol. Reprod. Dev. 63: 291–299, 2002. © 2002 Wiley‐Liss, Inc.
A mathematical model that predicts the force–frequency relationship of human skeletal muscle
Authors: Ding Jun , Wexler Anthony S. , Binder‐Macleod Stuart A. 
Published: October 2002

AbstractIn previous work we developed and validated a mathematical model that predicted force output from skeletal muscles subjected to six‐pulse stimulation trains under isometric condition. The current study investigated the model's ability to predict force responses to longer stimulation trains under both nonfatigued and fatigued conditions. Using the six‐pulse train model to predict the force produced by longer stimulation trains showed that the model was successful, but a modified parameter identification scheme was required. For most of the trains tested the model accounted for 95% of the variance in the experimental forces produced by stimulation trains, with mean frequencies from 12.5 to 100 HZ, train durations from 485 to 1000 ms, and number of pulses from 14 to 50 for both nonfatigued and fatigued muscles. The success of our mathematical model in predicting forces produced by stimulations with a wide range of frequencies, durations, and number of pulses implies great potential of the model for the identification of optimal activation patterns that should be used during functional electrical stimulation. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 477–485, 2002
Dominating sets for rectilinear center location problems with polyhedral barriers
Authors: Dearing P.M. , Hamacher H.W. , Klamroth K. 
Published: October 2002

AbstractIn planar location problems with barriers one considers regions which are forbidden for the siting of new facilities as well as for trespassing. These problems are important since they model various actual applications. The resulting mathematical models have a nonconvex objective function and are therefore difficult to tackle using standard methods of location theory even in the case of simple barrier shapes and distance functions. For the case of center objectives with barrier distances obtained from the rectilinear or Manhattan metric, it is shown that the problem can be solved in polynomial time by identifying a dominating set. The resulting genuinely polynomial algorithm can be combined with bound computations which are derived from solving closely connected restricted location and network location problems. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 647–665, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10038
Sparse matrix element topology with application to AMG(e) and preconditioning
Authors: Vassilevski Panayot S. 
Published: October 2002

AbstractThis paper defines topology relations of elements treated as overlapping lists of nodes. In particular, the element topology makes use of element faces, element vertices and boundary faces which coincide with the actual (geometrical) faces, vertices and boundary faces in the case of true finite elements. The element topology is used in an agglomeration algorithm to produce agglomerated elements (a non‐overlapping partition of the original elements) and their topology is then constructed, thus allowing for recursion. The main part of the algorithms is based on operations on Boolean sparse matrices and the implementation of the algorithms can utilize any available (parallel) sparse matrix format. Applications of the sparse matrix element topology to AMGe (algebraic multigrid for finite element problems), including elementwise constructions of coarse non‐linear finite element operators are outlined. An algorithm to generate a block nested dissection ordering of the nodes for generally unstructured finite element meshes is given as well. The coarsening of the element topology is illustrated on a number of fine‐grid unstructured triangular meshes. Published in 2002 by John Wiley & Sons, Ltd.
Distortion measure of trilinear mapping. Application to 3‐D grid generation
Authors: Branets L. V. , Garanzha V. A. 
Published: October 2002

AbstractDistortion measures for polylinear mappings are investigated. It is shown that certain distortion measures satisfy the maximum principle which allows us to obtain upper bounds on the distortion measures for hexahedral cells and other types of elements widely used in the finite element method. These estimates allow to apply a maximum‐norm optimization technique for spatial mappings in the case of finite element grids consisting of hexahedra. A global hexahedral grid untangling procedure suggested earlier was tested on hard 3‐D examples demonstrating its ability to work in a black box mode and its high level of robustness. Copyright © 2002 John Wiley & Sons, Ltd.
Frequent FGFR3 mutations in urothelial papilloma
Authors: van Rhijn Bas W. G. , Montironi Rodolfo , Zwarthoff Ellen C. , Jöbsis Adriaan C. , van der Kwast Theo H. 
Published: October 2002

AbstractActivating point mutations in the FGFR3 gene occur frequently in low‐grade and low‐stage bladder carcinomas, whereas they are rare in high‐grade carcinomas. This study investigates the incidence of FGFR3 mutations in 12 urothelial papillomas and 79 pTaG1 tumours which were regraded according to the 1998 WHO/ISUP classification system, resulting in 62 papillary urothelial neoplasms of low malignant potential (PUNs‐LMP) and 17 low‐grade papillary urothelial carcinomas (LG‐PUCs). FGFR3 mutation analysis of 21 ovarian Brenner tumours was also performed. Seventy‐seven cases were detected with a mutation in the FGFR3 gene. The mutations were exclusively found in bladder neoplasms. In urothelial papilloma, generally considered a benign lesion, 9/12 (75%) mutations were found. This report is the first to describe a genetic defect in urothelial papilloma. A comparable percentage of mutations was found in PUNs‐LMP (85%) and LG‐PUCs (88%). No mutations were found in matched normal DNA from bladder tumour patients. The mean follow‐up was 5.78 years (range 0.21–17.60 years). Five patients developed high‐grade papillary urothelial carcinoma from 2.5 to 12 years after first diagnosis. Two patients died of bladder cancer. The mean number of recurrences (recurrence rate) per year was 0.03, 0.21, and 0.46, respectively, for papilloma, PUN‐LMP, and LG‐PUC. Urothelial papilloma is a rare lesion with a benign natural behaviour compared with PUN‐LMP and LG‐PUC of the bladder, but from a molecular perspective, papillomas should be classified together with all well‐differentiated urothelial neoplasms. Copyright © 2002 John Wiley & Sons, Ltd.
Amphiphilic ABA triblock copolymer as surfactant in syntheses of microlatexes bearing cationic groups
Authors: Ni Pei‐Hong , Zhang Ming‐Zu , Zhuge Lan‐Jian , Fu Shou‐Kuan 
Published: October 2002

AbstractPolystyrene microlatexes have been prepared by conventional emulsion polymerization with a novel amphiphilic water‐soluble ABA triblock copolymer, poly[2‐(dimethylamino)ethyl methacrylate]15‐b‐poly(propylene oxide)36‐b‐poly[2‐(dimethyl‐amino)ethyl methacrylate]15 (PDMAEMA15‐PPO36‐PDMAEMA15), as a polycationic emulsifier under acidic or neutral conditions. The ABA triblock copolymer was developed by oxyanion‐initiated polymerization in our laboratory. In this study, it acted well both as a polycationic polymeric surfactant to form block copolymeric micelles for emulsion polymerization and as a stabilizer to be anchored into the polystyrene microlatex or adsorbed onto its surface. The results obtained with various copolymer concentrations and different pH media showed that microlatex diameters decreased remarkably with increased concentration of this ABA triblock copolymeric emulsifier, but were not as much affected by the pH of media within the experimental range of 3.4–7.0. The observed difference of the particle sizes from transmission electron microscopy and dynamic light scattering measurements is discussed in terms of the effect of the absorbed surfactants and their electrical double layers. This difference has led to the formation of a cationic polyelectrolyte fringe on the surface of microspheres. The final microlatexes were characterized with respect to total conversion, particle diameter, and particle size distribution as well as colloidal stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3734–3742, 2002
Nickel(II) and palladium(II) complexes with α‐dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane, tris(pentafluorophenyl)borane, or triethylaluminum cocatalyst systems
Authors: Berchtold Bernd , Lozan Vasile , Lassahn Paul‐Gerhard , Janiak Christoph 
Published: October 2002

AbstractNickel(II) and palladium(II) complexes with α‐dioxime ligands dimethylglyoxime, diphenylglyoxime, and 1,2‐cyclohexanedionedioxime represent six new precatalysts for the polymerization of norbornene that can be activated with methylaluminoxane (MAO), the organo‐Lewis acid tris(pentafluorophenyl)borane [B(C6F5)3], and triethylaluminum (TEA) AlEt3. The palladium but not the nickel precatalysts could also be activated by B(C6F5)3 alone, whereas two of the three nickel precatalysts but none of the palladium systems are somewhat active with only TEA as a cocatalyst. It was possible to achieve very high polymerization activities up to 3.2 · 107 gpolymer/molmetal · h. With the system B(C6F5)3/AlEt3, the activation process can be formulated as the following two‐step reaction: (1) B(C6F5)3 and TEA lead to an aryl/alkyl group exchange and result in the formation of Al(C6F5)nEt3−n and B(C6F5)3−nEtn; and (2) Al(C6F5)nEt3−n will then react with the precatalysts to form the active species for the polymerization of norbornene. Variation of the B:Al ratio shows that Al(C6F5)Et2 is sufficient for high activation. Gel permeation chromatography indicated that it was possible to control the molar mass of poly(norbornene)s by TEA or 1‐dodecene as chain‐transfer agents; the molar mass can be varied in the number‐average molecular weight range from 2 · 103 to 9 · 105 g · mol−1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3604–3614, 2002
Synthesis and crosslinking of polyethers that have mesogenic cores and propargyl groups
Authors: Bonet J. , Callau L. , Reina J. A. , Galià M. , Cádiz V. 
Published: October 2002

AbstractWe modified poly(epichlorohydrin) (PECH) with biphenyl carboxylic and naphthalene carboxylic acid derivatives which contains propargyloxy moieties. The linear polymers were characterized by NMR and IR spectroscopy, elemental analysis, DSC and TGA. We obtained only one side chain liquid crystalline. A smectic A mesophase of this biphenyl derivative was identified by DSC, light polarized optical microscopy and X‐ray diffraction. Thermal crosslinking of the aryl propargyl ether group via sigmatropic rearrangement took place while the material was in the isotropic phase. Partially curing this reactive liquid crystalline polymer resulted in the formation of an anisotropic elastomer when the curing was radically initiated in the range of mesophase stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3883–3892, 2002
Synthesis and characterization of luminescent copolymers containing iminodibenzyl and divinylbenzene chromophores
Authors: Wu Tzi‐Yi , Chen Yun 
Published: October 2002

AbstractNew conjugated copolymers containing alternating N‐hexyl‐3,8‐iminodibenzyl and divinylbenzene chromophores {poly(N‐hexyl‐3,8‐iminodibenzyl‐1,2‐ethenylene‐2,5‐dihexyloxy‐1,4‐phenylene‐1,2‐ethenylene) (P1) and poly[N‐hexyl‐3,8‐iminodibenzyl‐2,5‐bis(hexyloxy)cyanoterephthalidene] (P2)} were synthesized according to Wittig and Knoevenagel polymerization. A copolymer containing alternating carbazole and divinylbenzene derivatives {poly[9‐(2‐ethylhexyl)‐3,6‐carbazole‐1,2‐ethenylene‐2,5‐dihexyloxy‐1,4‐phenylene‐1,2‐ethenylene] (P3)} was also synthesized for comparison. The copolymers were soluble in common organic solvents such as tetrahydrofuran and toluene. Absorption and photoluminescence measurements revealed that cyano substitution at the vinylene moiety in P2 brought about a significant bathochromic shift and led to an electroluminescence color change from green to orange. The band edge energies of the copolymers were estimated from cyclic voltammograms and optical band gaps. P1 and P3 showed similar highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels, indicating that the electron‐donating abilities of the iminodibenzyl and carbazole chromophores were comparable. However, compared with those of P1 and P3, the HOMO and LUMO levels of P2 were greatly reduced because of conjugating and electron‐withdrawing CN groups. The threshold electric field of an Al/P1/ITO glass single‐layer light‐emitting diode was approximately 10 × 105 V/cm, whereas those for P2 and P3 were 7.5 and 16 × 105 V/cm, respectively. The electroluminescence emission maxima of P1–P3 were 498, 514, and 559 nm, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3847–3857, 2002
Polymerization of vinyl ethers with transition‐metal catalysts: An examination of the stereoregularity of the formed polymers
Authors: Kawaguchi Takaaki , Sanda Fumio , Masuda Toshio 
Published: October 2002

AbstractThe polymerization of isobutyl vinyl ether (IBVE) and tert‐butyl vinyl ether (TBVE) was carried out with metallocene and nonmetallocene catalysts, and the stereoregularity of the formed polymers was examined with 13C NMR spectroscopy. IBVE afforded polymers with 63–68% dyad isotacticity by polymerization with mixtures of metallocene catalysts and methyl aluminoxane as a cocatalyst in toluene as a solvent. However, TBVE yielded polymers with 47–52% dyad isotacticity (21–28% triad isotacticity) under the same conditions, the isotacticity being lower than that of poly(isobutyl vinyl ether) (PIBVE). Nonmetallocene catalysts, including Ti, Zr, and Hf complexes with two phenoxy imine chelate ligands, provided PIBVE and poly(tert‐butyl vinyl ether) with 63–68 and 45–51% dyad isotacticity, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3938–3943, 2002
Investigation of polycondensation through the copolycondensation of preformed oligomers and bisphenols by a two‐stage solution reaction with tosyl chloride, dimethylformamide, and pyridine
Authors: Higashi Fukuji , Sugishita Kanako 
Published: October 2002

AbstractA two‐stage copolycondensation of an equimolar mixture of isophthalic acid and terephthalic acid first with a bisphenol (BP) and then with another BP was carried out with a tosyl chloride/dimethylformamide/pyridine condensing agent. When the preformed oligomers from a BP with no substituent or a methyl substituent were allowed to react with another BP comonomer containing polar SO2, CO, or Cl groups, the copolycondensation was significantly promoted. Such effects were absent with the unsubstituted BP and the methyl derivative. In addition, during the reaction of oligomers from BPs with polar groups, a similarly polar BP did not react so effectively, and the unsubstituted BP did not have any effect on the copolycondensation. On the basis of the sequence distributions for the resultant copolymers determined by 1H NMR, it was likely that the copolycondensation could be promoted when the second comonomers were randomly distributed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4024–4031, 2002
Effect of the sulfonic acid group on copolymers of aniline and toluidine with m‐aminobenzene sulfonic acid
Authors: Rao Palle Swapna , Sathyanarayana D. N. 
Published: October 2002

AbstractThis article describes the results of the preparation and characterization of self‐doped conducting copolymers of aniline and toluidine with m‐aminobenzene sulfonic acid. The copolymers have an intrinsic acid group that is capable of doping polyaniline. Spectroscopic, morphological, and electrical conductivity studies have provided insight into the structural and electronic properties of the copolymers. The differences in the properties of polyaniline and polytoluidine due to the sulfonic acid ring substituent on the phenyl ring are discussed. The scanning electron micrographs of the copolymers reveal regions of sharp‐edged, needle‐shaped structures, whereas the X‐ray diffraction patterns show that the copolymers are relatively more crystalline in nature. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4065–4076, 2002