bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of annealing on the microphase separated behavior and properties of PDMS–MDI–PEG multiblock copolymer films
Authors: Fang Hongxia , Feng Libang , You Bo , Wu Limin 
Published: December 2006

AbstractA model multiblock copolymer based on (Poly dimethylsiloxane) (PDMS),–4, 4′‐diphenylmethanediisocyanate (MDI)–(poly ethylene glycol) (PEG) was synthesized by employing two step growth polymerization technique. The effect of annealing on microphase separation of the copolymer surface and bulk, surface composition, hydrogen‐bonding and some properties was investigated by AFM, SAXS, XPS, FTIR, contact angle measurement, and protein adsorption experiment, respectively. It was found that increasing the annealing temperature availed formation of microphase separation and surface enrichment of PDMS, which was accompanied by increase in average interdomain spacing, long period, and the crystallizing degree in the hard domains. But the best microphase separated structure seemed to occur at the annealing temperature of 140 °C; exorbitant annealing temperature might demolish the ordered structure. The annealing temperature dependence of microphase separation was further confirmed by the changes in urea hydrogen‐bonding and melting points characterized by FTIR and DSC, respectively. Protein adsorption experiments revealed that all annealed copolymer films possessed the low protein adsorption. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 208–217, 2007
Higher order structural analysis of stereocomplex‐type poly(lactic acid) melt‐spun fibers
Authors: Furuhashi Yukiko , Kimura Yoshiharu , Yamane Hideki 
Published: December 2006

AbstractThe higher order structure of stereocomplex‐type poly(lactic acid) melt‐spun fibers of an equimolar blend of poly(L‐lactic acid) and poly(D‐lactic acid) was analyzed with wide‐angle X‐ray diffraction (WAXD) and birefringence measurements. Two different crystalline structures were observed in the fibers: α‐form homocrystals and stereocomplex crystals. The weight fractions of the two crystals were estimated with the WAXD integrated intensity data. The crystalline orientation factors were obtained from the WAXD measurements. Well‐oriented homocrystals formed during a drawing process at the crystallization temperature of the homocrystal. Drawing above this temperature caused the stereocomplex crystal to be formed. The crystalline orientation tended to be lower with increasing drawing temperatures. Through the combination of the intrinsic birefringence and the fractions of the α‐form homocrystals and stereocomplex crystals, the birefringence of the amorphous phase was evaluated. The amorphous birefringence stayed positive and decreased with increasing drawing temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 218–228, 2007
A knowledge‐based move set for protein folding
Authors: Chen William W. , Yang Jae Shick , Shakhnovich Eugene I. 
Published: December 2006

AbstractThe free energy landscape of protein folding is rugged, occasionally characterized by compact, intermediate states of low free energy. In computational folding, this landscape leads to trapped, compact states with incorrect secondary structure. We devised a residue‐specific, protein backbone move set for efficient sampling of protein‐like conformations in computational folding simulations. The move set is based on the selection of a small set of backbone dihedral angles, derived from clustering dihedral angles sampled from experimental structures. We show in both simulated annealing and replica exchange Monte Carlo (REMC) simulations that the knowledge‐based move set, when compared with a conventional move set, shows statistically significant improved ability at overcoming kinetic barriers, reaching deeper energy minima, and achieving correspondingly lower RMSDs to native structures. The new move set is also more efficient, being able to reach low energy states considerably faster. Use of this move set in determining the energy minimum state and for calculating thermodynamic quantities is discussed. Proteins 2007. © 2006 Wiley‐Liss, Inc.
Impurity‐related optical properties in rectangular‐transverse section GaAs–Ga1–xAlxAs quantum well wires: Hydrostatic pressure and electric field effects
Authors: González J. W. , López S. Y. , Rodríguez A. H. , Porras‐Montenegro N. , Duque C. A. 
Published: December 2006

AbstractUsing a variational procedure within the effective mass approximation, we have calculated the influence of an applied electric field and hydrostatic pressure on the shallow‐impurity‐related optical properties in a rectangular‐transverse section GaAs–Ga1–x Alx As quantum well wire. The electric field is applied in the plane of the transverse section of the wire and different angular directions have been considered. The results presented are for the impurity binding energy, its corresponding density of impurity states, and impurity‐related transition energy and polarizability. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the ductile response dependence upon phase transformation in diamond turning of semiconductors
Authors: Jasinevicius R. G. , Pizani P. S. 
Published: December 2006

AbstractIt is well established that during machining, materials with lower hardness presents higher ductility. However, in the machining of semiconductor crystals the brittle to ductile transition may not strictly follow this rule. This paper intends to show that the extent of the ductile response of monocrystalline semiconductors can not be related to its microhardness value, since the plastic behavior of semiconductor crystals is related to a phase transformation induced by pressure/stress. This was investigated by carrying out microindentation and single point diamond turning tests in three different semiconductors, InSb, GaAs and Si[001]‐oriented single crystals. Based upon tests results it is observed that the onset of brittle behavior is brought forward to semiconductors with higher transition pressure value. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐pressure X‐ray diffraction study of ternary and non‐stoichiometric PbTe and PbSe crystals
Authors: Ovsyannikov Sergey V. , Shchennikov Vladimir V. , Manakov Andrey Y. , Likhacheva Anna Y. , Berger Ivan F. , Ancharov Alexey I. , Sheromov Mikhail A. 
Published: December 2006

AbstractThe paper reports the pressure‐induced phase transitions observed in ternary PbTe and PbSe compounds (Pb1–x Snx Te, Pb1–x Mnx Te, Pb1–x Snx Se) and non‐stoichiometric PbTe ones (Pb0.55Te0.45, Pb0.45Te0.55) at room temperature in the range of 0 to14 GPa by means of angle‐dispersive X‐ray diffraction (ADXRD). The structure of the intermediate high‐pressure phase appearing above ∼6 GPa for all PbTe‐based compounds was established to be Pnma (orthorhombic), like in binary PbTe. The patterns of the intermediate high‐pressure phase of Pb1–x Snx Se (x = 0.125) were found to correspond entirely neither to GeS nor to orthorhombic Pnma, but the calculated reflections for GeS type were closer to the experimental ones. A model of the phase transformations is discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Post‐spinel transition and magnetic properties of LiMn2O4
Authors: Yamaura K. , Huang Q. , Zhang L. , Takada K. , Baba Y. , Nagai T. , Matsui Y. , Kosuda K. , Takayama‐Muromachi E. 
Published: December 2006

AbstractA post spinel transition of LiMn2O4 was recently found at 6 GPa. The high‐pressure form crystallizes into a double chain‐type structure, isostructural with CaFe2O4 (orthorhombic; Pnma). The orthorhombic unit cell parameters were found anisotropically dependent on the heating condition; it varies ∼0.5% while less than ∼0.1% along the chain direction, probably reflecting nature of the anisotropic structure basis. The form is magnetic due to the chain arrangement of the Mn magnetic moments and a magnetically glassy feature was found at ∼10 K being similar with what was found for the spinel‐type LiMn2O4 at ∼25 K. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Random cubic planar graphs
Authors: Bodirsky Manuel , Kang Mihyun , Löffler Mike , McDiarmid Colin 
Published: December 2006

AbstractWe show that the number of labeled cubic planar graphs on n vertices with n even is asymptotically αn−7/2ρ−nn!, where ρ−1 ≐ 3.13259 and α are analytic constants. We show also that the chromatic number of a random cubic planar graph that is chosen uniformly at random among all the labeled cubic planar graphs on n vertices is three with probability tending to e ≐ 0.999568 and four with probability tending to 1 − e as n → ∞ with n even. The proof given combines generating function techniques with probabilistic arguments. © 2006 Wiley Periodicals, Inc. Random Struct. Alg., 2007
A correlated frailty model with long‐term survivors for estimating the heritability of breast cancer
Authors: Locatelli Isabella , Rosina Alessandro , Lichtenstein Paul , Yashin Anatoli I. 
Published: December 2006

AbstractThe aim of this study is to investigate the role of genetics and environment in susceptibility to breast cancer (frailty). An interdisciplinary approach was adopted, combining a correlated frailty‐mixture model with genetic equations, allowing for decomposition of the frailty variance into genetic and environmental components. In addition, the possibility that a fraction of the population under study is ‘immune’ to the disease is evaluated, and changes in heritability estimates introducing a fraction of non‐susceptible individuals are determined. The methodology is applied to breast cancer data from the Swedish Twin Registry, including information about all female monozygotic and dizygotic twin pairs born in Sweden between 1886 and 1967. The inferential problem is solved in a Bayesian framework and the numerical work is carried out using Markov chain Monte Carlo (MCMC) methods. Copyright © 2006 John Wiley & Sons, Ltd.
Type‐A behavior in a multinational organization: a study of two countries
Authors: Jamal Muhammad 
Published: December 2006

AbstractThis study examined the relationship of global Type A and its components (time pressure and hard driving/competitiveness) with job performance, job satisfaction and health problems among employees working in a multinational company in Malaysia (N = 305) and Pakistan (N = 325).Data were collected by means of a structured questionnaire from employees concerning Type‐A behavior, job satisfactions and health problems. Job performance data were obtained from the company's personnel files. The immediate supervisor provided the job performance rating annually for all employees. Bivariate multiple regressions were used to analyze the data. Global Type A and its two components were not related to job performance in either countries. Global Type A and the components time pressure and hard driving/competitiveness were significantly related to job satisfaction and health problems in both countries. Some support for the differential effects of Type‐A behavior components on health problems was noted in both samples. Implications of findings are discussed for international and cross‐cultural research. Copyright © 2006 John Wiley & Sons, Ltd.
Biosynthesis and biotransformation of ether lipids
Authors: Mangold Helmut K. , Weber Nikolaus 
Published: December 2006

AbstractSome naturally occurring as well as synthetic ether lipids are biologically active. In certain cases, the effects of these substances are enhanced, in others, they are inhibited by compounds that were isolated from natural sources or prepared by chemical synthesis. The biotrans‐formation of natural or “unnatural” ether lipids in microorganisms, plant or animal tissue also can lead to substances that elicit biological effects. The production of such compounds through various biotechnological techniques is a field wide open for future exploration. In addition to animal cell cultures, plant cell cultures may become useful tools in biomedical studies concerned with ether lipids.
The degradation of platelet‐activating factor and related lipids: Susceptibility to phospholipases C and D
Authors: Wilcox Rebecca W. , Wykle Robert L. , Schmitt Jeffery D. , Daniel Larry W. 
Published: December 2006

Abstract1‐O‐Octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine (ET‐18‐OCH3) is an ether‐linked lipid that exhibits selective cytotoxicity toward several types of tumor cells and is relatively inactive toward normal cells under the same conditions of treatment. The mechanism of this selective cytotoxicity is unknown. We conducted studies to determine whether this compound is metabolized by phospholipases C and D and, if so, whether sensitive and resistant cells differ in their ability to degrade ET‐18‐OCH3 by these enzymes. We have examined the metabolism of the L‐isomer of ET‐18‐OCH3, 1‐O‐octadecyl‐2‐O‐methyl‐sn‐glycero‐3‐phosphocholine (L‐ET‐18‐OCH3), by lysophospholipase D of rat liver microsomes and by a phospholipase D from the marine bacteriumVibrio damsela. The metabolism of L‐ET‐18‐OCH3 was also examined in cell culture using Madin‐Darby canine kidney cells, human promyelocytic leukemia cells and human myelocytic leukemia cells. In these studies, L‐ET‐18‐OCH3 and related 1‐O‐alkyl‐linked phosphocholine analogs radiolabeled with3H in the 1‐O‐alkyl chain were used.L‐ET‐18‐OCH3 was not hydrolyzed by lysophospholipase D from rat liver microsomes under conditions where cleavage of 1‐O‐alkyl‐2‐lyso‐sn‐glycero‐3‐phosphocholine was observed. However, phospholipase D from the marine bacteriumV. damsela readily hydrolyzed L‐ET‐18‐OCH3 to 1‐O‐[3H]octadecyl‐2‐O‐methyl‐sn‐glycero‐3‐phosphate, demonstrating that L‐ET‐18‐OCH3 can be degraded by a phospholipase D. Platelet‐activating factor (PAF) and lyso‐PAF were also substrates for the bacterial phospholipase D.When intact cells were incubated with radiolabeled L‐ET‐18‐OCH3 a product was formed that was identified as 1‐O‐[3H]octadecyl‐2‐O‐methyl‐sn‐glycerol. There are two mechanisms that could account for the appearance of this product. The first involves cleavage of the compound by a phospholipase C, resulting in direct release of the diglyceride. The second possible mechanism involves cleavage by a phospholipase D to form the phosphatidic acid analog with subsequent hydrolysis to the diglyceride by a phosphohydrolase. Preliminary data support the phospholipase C‐type mechanism. Regardless of which mechanism operates in intact cells, the metabolic degradation of L‐ET‐18‐OCH3 does not appear to be a significant factor in the selective cytotoxicity of this antitumor agent.
Increased membrane permeability for an antitumoral alkyl lysophospholipid in sensitive tumor cells
Authors: Storch Joachim , Munder Paul G. 
Published: December 2006

AbstractWe have investigated cellular sensitivity to the antitumoral alkyl lysophospholipid (ALP) 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine (ET‐18‐OCH3) in vitro. The permeation of this lipid into the cell was not influenced by metabolic inhibitors of ATP biosynthesis. ET‐18‐OCH3 uptake was not saturable within sublytic concentrations, but could be inhibited in part by cytochalasin B (CB) and dipyridamole. The activation energy of the CB‐sensitive uptake process was increased up to threefold compared to CB‐insensitive uptake. ET‐18‐OCH3 influx and equilibrium binding of ET‐18‐OCH3 were decreased in a fibrosarcoma cell variant (MethA) selected for ET‐18‐OCH3 resistance. The resistant MethA cells were also less sensitive to cytolysis by lysophosphatidylcholine and other ALP. After 72 hr, the resistant MethA cells had metabolized only 11.8% more of the absorbed ET‐18‐OCH3 than sensitive MethA cells. However, they tolerated at least a 30‐fold concentration of this ALP. The uptake mechanism, which could be inhibited by CB, was less active in resistant MethA cells and several other ALP‐resistant cell lines. The concentration of CB, required for maximal uptake inhibition, was increased more than four times in the ALP‐sensitive tumor cell lines. CB‐specific ET‐18‐OCH3 uptake was also enhanced after virus transformation of 3T3 fibroblasts by SV 40. Dipyridamole retarded the ET‐18‐OCH3‐mediated cell destruction.
Accumulation of an alkyl lysophospholipid in tumor cell membranes affects membrane fluidity and tumor cell invasion
Authors: van Blitterswijk Wim J. , Hilkmann Henk , Storme Guy A. 
Published: December 2006

AbstractTumor cells grown in the presence of 1‐O‐alkyl‐2‐O‐methylglycero‐3‐phosphocholine (AMG‐PC) accumulated this ether lipid in their membranes. Depending on the cell type and the dose of the compound, up to 17% of the total phospholipids of the purified plasma membranes consisted of authentic AMG‐PC. Extensive incorporation of the agent resulted in a decrease in plasma membrane fluidity and inhibition of tumor cell invasiveness in embryonic chick heart fragments. The extent of AMG‐PC incorporation and fluidity change was not strictly correlated with the degree to which tumor cell invasion was inhibited.
Substrate specificity ofO‐alkylglycerol monooxygenase (E.C. 1.14.16.5), solubilized from rat liver microsomes
Authors: Kötting Jochem , Unger Clemens , Eibl Hansjörg 
Published: December 2006

AbstractSynthetic alkyl lysophospholipids (ALP) show antineoplastic activity. In the present discussion, the cytotoxicity of ALP is attributed to their accumulation in tumor cells. Some neoplastic cell species, in contrast to normal cells, cannot metabolize ALP because of a lack ofO‐alkylglycerol monooxygenase (AGMO) activity. To understand the metabolic fate of ether lipids and etherlinked phospholipids, AGMO substrate specificity studies were undertaken. Thirty‐five different natural and synthetic ether lipids and their metabolites (including a thioether) were tested as substrates for AGMO. The study revealed that the potent cytostatic substance, 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine is not a substrate for AGMO. Therefore, its selective toxicity to tumor cells cannot be based on the differences in direct detoxification of 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine by AGMO in normal and malignant cells. However, 1‐O‐octadeyl‐2‐O‐methyl‐rac‐glycerol, which can be formed by phospholipase C hydrolysis, is a good substrate for AGMO.
Ether lipids inhibit the effects of phorbol diester tumor promoters
Authors: Daniel Larry W. , Etkin Lori A. , Morrison Bennett T. , Parker Judy , Morris‐Natschke Susan , Surles Jefferson R. , Plantadosi Claude 
Published: December 2006

AbstractRecent studies have shown that the tumor promoter 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA) stimulates protein kinase C (PKC), whereas the ether‐linked phospholipid 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycerol‐3‐phosphocholine (ET‐18‐OCH3) inhibits PKC activity in vitro. Therefore, the antitumor effects of ET‐18‐OCH3 could be due to its inhibition of PKC activity and the effects of tumor promotion. TPA stimulates arachidonic acid release, prostaglandin synthesis, phosphatidylcholine synthesis and the degradation of phosphatidylcholine by phospholipase C in Madin Darby canine kidney (MDCK) cells. Therefore, we have determined the effects of ET‐18‐OCH3 on these consequences of TPA stimulation. Preliminary experiments determined that ET‐18‐OCH3 inhibited PKC partially purified from MDCK cells by ion‐exchange chromatography on DEAE‐cellulose. In addition, ET‐18‐OCH3, inhibited the TPA‐stimulated phosphorylation of a 40,000‐dalton protein in intact MDCK cells. These data indicate that ET‐18‐OCH3 is an effective inhibitor of PKC activity in MDCK cells. In addition, ET‐18‐OCH3 was found to inhibit arachidonic acid release and prostaglandin synthesis. The inhibition of prostaglandin synthesis appears to be secondary to inhibition of arachidonic acid release, since ET‐18‐OCH3 does not inhibit TPA‐stimulated synthesis of prostaglandin H synthase or the activity of the enzyme directly (Parker, J., Daniel, L. W., and Waite, M. [1987]J. Biol. Chem. 262, 5385–5393). ET‐18‐OCH3 also inhibits TPA‐stimulated phosphatidylcholine synthesis and phosphatidylcholine degradation by phospholipase C. These data provide evidence that the antineoplastic ether lipids inhibit the biochemical effects of the tumor promoter TPA in intact cells and indicate that this inhibition may have a role in their biological activities.
Antitumor activity of synthetic alkylphospholipids with or without PAF activity
Authors: Kudo Ichiro , Nojima Shoshichi , Chang Hyeun Wook , Yanoshita Ryohei , Hayashi Hidetoshi , Kondo Eri , Nomura Hiroaki , Inoue Keizo 
Published: December 2006

Abstract1‐O‐Octadecyl‐2‐O‐methyl‐sn‐glycero‐3‐phosphocholine (ET‐18‐OMe) has been reported to possess definite antitumor activity in vivo. Twenty‐two alkyl lysophospholipid analogs were chemically synthesized, and their antitumor activity against mouse experimental tumors (Sarcoma 180, MM46, P388) was examined. Among them, 1‐O‐octadecyl‐2‐O‐acetoacetyl‐rac‐glycerol‐3‐phosphocholine was found to show antitumor activity similar to ET‐18‐OMe with less acute toxicity.Intravenous injection of the ET‐18‐OMe withsn‐3 configuration retarded the subcutaneous growth of Sarcoma 180 cells effectively, while the growth inhibition by thesn‐1 isomer was much less effective. This stereospecificity was similar to that observed in their activities as platelet‐activating factor (PAF) agonists. The acetoacetyl compound, another PAF agonist, showed similar stereospecific antitumor action in vivo. These findings suggest that some alkyl lysophospholipids may activate host cells to a cytostatic stage against tumor cells in vivo through binding to a PAF receptor. Our preliminary results indicated that the responsible cells under these conditions might be primarily immature macrophages present in the bone marrow. No appreciable or even adverse stereospecificity was observed in the different sets of experiments where the activity of ET‐18‐OMe against MM46 tumor cells in vivo or the direct cytotoxicity against human promyelocytic leukemia HL‐60 cells in vitro was examined. Under, some conditions, the antitumor activity of ET‐18‐OMe in vivo may be revealed through direct cytotoxicity and/or modulation of the host defense system by “nonspecific” mechanisms. Some alkylphospholipids without PAF activity may also show antitumor activity through similar, “nonspecific” mechanisms.
Neoplastic cell inhibition with new ether lipid analogs
Authors: Noseda Alessandro , Berens Michael E. , Piantadosi Claude , Modest Edward J. 
Published: December 2006

AbstractBioactive phospholipid analogs of platelet‐activating factor (PAF) represent a new approach to cancer chemotherapy. Various modifications of the basic structure of PAF lead to different ether lipid (EL) analogs. Data from the evaluation of thioalkyl and amidoalkyl glycerophosphocholine and of glycerophosphoinositol EL analogs against different experimental tumors in vitro (HL60 and K562 human leukemia cells, BG1 and BG3 ovarian adenocarcinomas) are presented. Exclusion of trypan blue after short exposure to the drugs determined cytotoxicity, and a soft agarose clonogenic assay measured the ability of the analogs to inhibit tumor cell proliferation. The thioalkyl EL are very active against the cell lines using both end points, and the amidoalkyl EL showed efficacy against the leukemic cell lines, whereas the phosphoinositol EL are active only at high concentrations. Combined use of EL analogs, which are membrane‐interactive, with classical DNA‐interactive chemotherapeutic drugs revealed that the combinations have additive antiproliferative effects. These results are promising leads in the development of the anticancer potential of ether lipid analogs.