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Haeni JH, Irvin P, Chang W, Uecker R, Reiche P, Li YL, Choudhury S, Tian W, Hawley ME, Craigo B, Tagantsev AK, Pan XQ, Streiffer SK, Chen LQ, Kirchoefer SW, Levy J, Schlom DG. Room-temperature ferroelectricity in strained SrTiO3. Nature 2004; 430:758-61. [PMID: 15306803 DOI: 10.1038/nature02773] [Citation(s) in RCA: 493] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2004] [Accepted: 06/22/2004] [Indexed: 11/09/2022]
Abstract
Systems with a ferroelectric to paraelectric transition in the vicinity of room temperature are useful for devices. Adjusting the ferroelectric transition temperature (T(c)) is traditionally accomplished by chemical substitution-as in Ba(x)Sr(1-x)TiO(3), the material widely investigated for microwave devices in which the dielectric constant (epsilon(r)) at GHz frequencies is tuned by applying a quasi-static electric field. Heterogeneity associated with chemical substitution in such films, however, can broaden this phase transition by hundreds of degrees, which is detrimental to tunability and microwave device performance. An alternative way to adjust T(c) in ferroelectric films is strain. Here we show that epitaxial strain from a newly developed substrate can be harnessed to increase T(c) by hundreds of degrees and produce room-temperature ferroelectricity in strontium titanate, a material that is not normally ferroelectric at any temperature. This strain-induced enhancement in T(c) is the largest ever reported. Spatially resolved images of the local polarization state reveal a uniformity that far exceeds films tailored by chemical substitution. The high epsilon(r) at room temperature in these films (nearly 7,000 at 10 GHz) and its sharp dependence on electric field are promising for device applications.
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Choi KJ, Biegalski M, Li YL, Sharan A, Schubert J, Uecker R, Reiche P, Chen YB, Pan XQ, Gopalan V, Chen LQ, Schlom DG, Eom CB. Enhancement of ferroelectricity in strained BaTiO3 thin films. Science 2004; 306:1005-9. [PMID: 15528439 DOI: 10.1126/science.1103218] [Citation(s) in RCA: 467] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Biaxial compressive strain has been used to markedly enhance the ferroelectric properties of BaTiO3 thin films. This strain, imposed by coherent epitaxy, can result in a ferroelectric transition temperature nearly 500 degrees C higher and a remanent polarization at least 250% higher than bulk BaTiO3 single crystals. This work demonstrates a route to a lead-free ferroelectric for nonvolatile memories and electro-optic devices.
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Journal Article |
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Tenne DA, Bruchhausen A, Lanzillotti-Kimura ND, Fainstein A, Katiyar RS, Cantarero A, Soukiassian A, Vaithyanathan V, Haeni JH, Tian W, Schlom DG, Choi KJ, Kim DM, Eom CB, Sun HP, Pan XQ, Li YL, Chen LQ, Jia QX, Nakhmanson SM, Rabe KM, Xi XX. Probing Nanoscale Ferroelectricity by Ultraviolet Raman Spectroscopy. Science 2006; 313:1614-6. [PMID: 16973874 DOI: 10.1126/science.1130306] [Citation(s) in RCA: 273] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We demonstrated that ultraviolet Raman spectroscopy is an effective technique to measure the transition temperature (Tc) in ferroelectric ultrathin films and superlattices. We showed that one-unit-cell-thick BaTiO3 layers in BaTiO3/SrTiO3 superlattices are not only ferroelectric (with Tc as high as 250 kelvin) but also polarize the quantum paraelectric SrTiO3 layers adjacent to them. Tc was tuned by approximately 500 kelvin by varying the thicknesses of the BaTiO3 and SrTiO3 layers, revealing the essential roles of electrical and mechanical boundary conditions for nanoscale ferroelectricity.
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Bhisutthibhan J, Pan XQ, Hossler PA, Walker DJ, Yowell CA, Carlton J, Dame JB, Meshnick SR. The Plasmodium falciparum translationally controlled tumor protein homolog and its reaction with the antimalarial drug artemisinin. J Biol Chem 1998; 273:16192-8. [PMID: 9632675 DOI: 10.1074/jbc.273.26.16192] [Citation(s) in RCA: 173] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Artemisinin and its derivatives are important new antimalarial drugs. When Plasmodium falciparum-infected erythrocytes are incubated with [10-3H]dihydroartemisinin, several malaria-specific proteins become labeled. One of these proteins is the P. falciparum translationally controlled tumor protein (TCTP) homolog. In vitro, dihydroartemisinin reacts covalently with recombinant TCTP in the presence of hemin. The association between drug and protein increases with increasing drug concentration, plateauing at approximately 1 drug/TCTP molecule. By Scatchard analysis, there appear to be 2 hemin binding sites on TCTP with dissociation constants of approximately 18 microM. When the single cysteine moiety is blocked by pretreatment with iodoacetamide, hemin binding is not affected, whereas drug binding is reduced by two-thirds. Thus, TCTP reacts with artemisinin in situ and in vitro in the presence of hemin and appears to bind to hemin. The function of the malarial TCTP and the role of this reaction in the mechanism of action of artemisinin await elucidation.
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Baek SH, Jang HW, Folkman CM, Li YL, Winchester B, Zhang JX, He Q, Chu YH, Nelson CT, Rzchowski MS, Pan XQ, Ramesh R, Chen LQ, Eom CB. Ferroelastic switching for nanoscale non-volatile magnetoelectric devices. NATURE MATERIALS 2010; 9:309-314. [PMID: 20190772 DOI: 10.1038/nmat2703] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 01/25/2010] [Indexed: 05/28/2023]
Abstract
Multiferroics, where (anti-) ferromagnetic, ferroelectric and ferroelastic order parameters coexist, enable manipulation of magnetic ordering by an electric field through switching of the electric polarization. It has been shown that realization of magnetoelectric coupling in a single-phase multiferroic such as BiFeO(3) requires ferroelastic (71 degrees, 109 degrees) rather than ferroelectric (180 degrees) domain switching. However, the control of such ferroelastic switching in a single-phase system has been a significant challenge as elastic interactions tend to destabilize small switched volumes, resulting in subsequent ferroelastic back-switching at zero electric field, and thus the disappearance of non-volatile information storage. Guided by our phase-field simulations, here we report an approach to stabilize ferroelastic switching by eliminating the stress-induced instability responsible for back-switching using isolated monodomain BiFeO(3) islands. This work demonstrates a critical step to control and use non-volatile magnetoelectric coupling at the nanoscale. Beyond magnetoelectric coupling, it provides a framework for exploring a route to control multiple order parameters coupled to ferroelastic order in other low-symmetry materials.
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Letter |
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Baek SH, Park J, Kim DM, Aksyuk VA, Das RR, Bu SD, Felker DA, Lettieri J, Vaithyanathan V, Bharadwaja SSN, Bassiri-Gharb N, Chen YB, Sun HP, Folkman CM, Jang HW, Kreft DJ, Streiffer SK, Ramesh R, Pan XQ, Trolier-McKinstry S, Schlom DG, Rzchowski MS, Blick RH, Eom CB. Giant piezoelectricity on Si for hyperactive MEMS. Science 2011; 334:958-61. [PMID: 22096193 DOI: 10.1126/science.1207186] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Microelectromechanical systems (MEMS) incorporating active piezoelectric layers offer integrated actuation, sensing, and transduction. The broad implementation of such active MEMS has long been constrained by the inability to integrate materials with giant piezoelectric response, such as Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PMN-PT). We synthesized high-quality PMN-PT epitaxial thin films on vicinal (001) Si wafers with the use of an epitaxial (001) SrTiO(3) template layer with superior piezoelectric coefficients (e(31,f) = -27 ± 3 coulombs per square meter) and figures of merit for piezoelectric energy-harvesting systems. We have incorporated these heterostructures into microcantilevers that are actuated with extremely low drive voltage due to thin-film piezoelectric properties that rival bulk PMN-PT single crystals. These epitaxial heterostructures exhibit very large electromechanical coupling for ultrasound medical imaging, microfluidic control, mechanical sensing, and energy harvesting.
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Research Support, U.S. Gov't, Non-P.H.S. |
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Jang HW, Kumar A, Denev S, Biegalski MD, Maksymovych P, Bark CW, Nelson CT, Folkman CM, Baek SH, Balke N, Brooks CM, Tenne DA, Schlom DG, Chen LQ, Pan XQ, Kalinin SV, Gopalan V, Eom CB. Ferroelectricity in strain-free SrTiO3 thin films. PHYSICAL REVIEW LETTERS 2010; 104:197601. [PMID: 20866998 DOI: 10.1103/physrevlett.104.197601] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Indexed: 05/29/2023]
Abstract
Biaxial strain is known to induce ferroelectricity in thin films of nominally nonferroelectric materials such as SrTiO3. By a direct comparison of the strained and strain-free SrTiO3 films using dielectric, ferroelectric, Raman, nonlinear optical and nanoscale piezoelectric property measurements, we conclude that all SrTiO3 films and bulk crystals are relaxor ferroelectrics, and the role of strain is to stabilize longer-range correlation of preexisting nanopolar regions, likely originating from minute amounts of unintentional Sr deficiency in nominally stoichiometric samples. These findings highlight the sensitive role of stoichiometry when exploring strain and epitaxy-induced electronic phenomena in oxide films, heterostructures, and interfaces.
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Peters W, Ekong R, Robinson BL, Warhurst DC, Pan XQ. Antihistaminic drugs that reverse chloroquine resistance in Plasmodium falciparum. Lancet 1989; 2:334-5. [PMID: 2569137 DOI: 10.1016/s0140-6736(89)90522-9] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Letter |
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Torok DS, Ziffer H, Meshnick SR, Pan XQ, Ager A. Syntheses and antimalarial activities of N-substituted 11-azaartemisinins. J Med Chem 1995; 38:5045-50. [PMID: 8544181 DOI: 10.1021/jm00026a012] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A two-step reaction sequence between artemisinin and methanolic ammonia followed by treatment with Amberlyst 15 yielded 11-azaartemisinin in 65% yield. Substituting a variety of primary alkyl- and heteroaromatic amines for ammonia in the reaction sequence yields N-substituted 11-azaartemisinins in similar or greater yield. When Amberlyst 15 is replaced by a mixture of sulfuric acid/silica gel, both 11-azaartemisinin and the expected metabolite, 10-azadesoxyartemisinin, are formed in 45% and 15% yields, respectively. In vitro and in vivo test data for a number of novel N-substituted 11-azaartemisinins, against drug-resistant strains of Plasmodium falciparum, show they possess antimalarial activities equal to or greater than that of artemisinin. The most active derivative, N-(2'-acetaldehydo)-11-azaartemisinin, 17, was 26 times more active in vitro and 4 times more active in vivo than artemisinin.
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10
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Sufrin JR, Meshnick SR, Spiess AJ, Garofalo-Hannan J, Pan XQ, Bacchi CJ. Methionine recycling pathways and antimalarial drug design. Antimicrob Agents Chemother 1995; 39:2511-5. [PMID: 8585735 PMCID: PMC162974 DOI: 10.1128/aac.39.11.2511] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
5'-Deoxy-5'-(methylthio)adenosine (MTA) is an S-adenosylmethionine metabolite that is generated as a by-product of polyamine biosynthesis. In mammalian cells, MTA undergoes a phosphorolytic cleavage catalyzed by MTA phosphorylase to produce adenine and 5-deoxy-5-(methylthio)ribose-1-phosphate (MTRP). Adenine is utilized in purine salvage pathways, and MTRP is subsequently recycled to methionine. Whereas some microorganisms metabolize MTA to MTRP via MTA phosphorylase, others metabolize MTA to MTRP in two steps via initial cleavage by MTA nucleosidase to adenine and 5-deoxy-5-(methylthio)ribose (MTR) followed by conversion of MTR to MTRP by MTR kinase. In order to assess the extent to which these pathways may be operative in Plasmodium falciparum, we have examined a series of 5'-alkyl-substituted analogs of MTA and the related MTR analogs and compared their abilities to inhibit in vitro growth of this malarial parasite. The MTR analogs 5-deoxy-5-(ethylthio)ribose and 5-deoxy-5-(hydroxyethylthio)ribose were inactive at concentrations up to 1 mM, and 5-deoxy-5-(monofluoroethylthio)ribose was weakly active (50% inhibitory concentration = 700 microM). In comparison, the MTA analogs, 5'-deoxy-5'-(ethylthio)adenosine,5'-deoxy-5'-(hydroxyethylthio)ade nosine (HETA), and 5'-deoxy-5'-(monofluoroethylthio)adenosine, had 50% inhibitory concentrations of 80, 46, and 61 microM, respectively. Extracts of P. falciparum were found to have substantial MTA phosphorylase activity. Coadministration of MTA with HETA partially protected the parasites against the growth-inhibitory effects of HETA. Results of this study indicate that P. falciparum has an active MTA phosphorylase that can be targeted by analogs of MTA.
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research-article |
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11
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Lu H, Liu X, Burton JD, Bark CW, Wang Y, Zhang Y, Kim DJ, Stamm A, Lukashev P, Felker DA, Folkman CM, Gao P, Rzchowski MS, Pan XQ, Eom CB, Tsymbal EY, Gruverman A. Enhancement of ferroelectric polarization stability by interface engineering. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:1209-1216. [PMID: 22278910 DOI: 10.1002/adma.201104398] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 12/23/2011] [Indexed: 05/31/2023]
Abstract
By using theoretical predictions based on first-principle calculations, we explore an interface engineering approach to stabilize polarization states in ferroelectric heterostructures with a thickness of just several nanometers.
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Peters W, Ekong R, Robinson BL, Warhurst DC, Pan XQ. The chemotherapy of rodent malaria. XLV. Reversal of chloroquine resistance in rodent and human Plasmodium by antihistaminic agents. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 1990; 84:541-51. [PMID: 1981663 DOI: 10.1080/00034983.1990.11812509] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The inherent blood schizontocidal activities of five antihistaminic compounds, cyproheptadine hydrochloride (CYP), ketotifen hydrogen fumarate (KET), pizotyline hydrogen maleate (PIZ), azatadine maleate (AZAT) and loratadine (LOR) were examined against the following organisms: chloroquine-sensitive (CS) Plasmodium berghei and chloroquine-resistant (CR) P. yoelii ssp. NS in mice; and CS Tak 9 clone 96 and CR K1 strain of P. falciparum in vitro. Chloroquine, verapamil and desipramine were used as comparison standards. CYP, KET, PIZ were active against the CS strain in vivo with ED90 levels between 20 and 30 mg kg-1 (given sc daily for four days). They were slightly more active against the CR strain. AZA was active, but much less so than the other compounds. LOR, verapamil and desipramine were inactive in vivo at the doses tested. Against CS P. falciparum in vitro, all five antihistaminics and desipramine were active at EC50 concentrations ranging from about 50-80 mumol l-1, while verapamil was only active at 175 mumol l-1. Against the CR strain of this parasite, CYP, PIZ and LOR were slightly more active than against the CS strain, but KET, AZAT, desipramine and verapamil were significantly less active. The action of all these compounds in combination with chloroquine was then examined both in vivo and in vitro. The ability of verapamil and desipramine to reverse chloroquine resistance in vitro was confirmed, but only a low level of reversal was seen with these compounds in vivo. However, CYP, KET, PIZ and AZAT produced a marked reversal of chloroquine resistance both in vivo and in vitro. The implications of these observations in relation to further laboratory and clinical research are discussed.
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Pu YM, Torok DS, Ziffer H, Pan XQ, Meshnick SR. Synthesis and antimalarial activities of several fluorinated artemisinin derivatives. J Med Chem 1995; 38:4120-4. [PMID: 7562948 DOI: 10.1021/jm00020a028] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The carbonyl groups in several artemisinin derivatives were converted into geminal difluorinated compounds on treatment with diethylaminosulfur trifluoride. A number of other mono- and polyfluorinated artemisinin derivatives were prepared. Their in vitro antimalarial activities were all equal to or greater than the nonfluorinated analogs or precursors.
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Wu J, Ishikawa N, Takeda T, Tanaka Y, Pan XQ, Sato M, Todoroki T, Hatakeyama R, Itai Y. The functional hepatic volume assessed by 99mTc-GSA hepatic scintigraphy. Ann Nucl Med 1995; 9:229-35. [PMID: 8770291 DOI: 10.1007/bf03168406] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The accuracy of measurement of the functional hepatic volume by single photon emission computed tomography (SPECT) with 99mTc-galactosyl serum albumin (99mTc-GAS) was evaluated. 99mTc-GSA planar scintigraphic images were obtained dynamically and the hepatic SPECT imaging was then performed in 25 patients with hepatobiliary tumors. The patients were divided into 4 groups with normal hepatic function, and mild, moderate and severe hepatic dysfunction. The functional hepatic volume determined by SPECT was compared with the morphological hepatic volume determined by compute tomography. The ratio of the hepatic volumes obtained by the two methods was calculated. The mean hepatic volume ratio was 96.6 +/- 2.3% in the normal hepatic function group and 95.9 +/- 2.2% in the mild dysfunction group (n.s.). In both the moderate and severe hepatic dysfunction groups, the hepatic volume ratio was smaller than that in the normal group (87.9 +/- 5.2%, p < 0.0001, and 71.9 +/- 7.6%, p < 0.0001, respectively). There was a linear correlation between the hepatic volume ration and various indices of reserve hepatic function, such as LHL15 (r = 0.83, p < 0.0001), HH15(r = 0.74, p < 0.0001), and ICG15 (r = 0.75, p < 0.0005). These results indicate that the hepatic volume ratio is proportional to the severity of hepatic dysfunction, and suggest that the functional hepatic volume measured with 99mTc-GSA faithfully reflects the functioning hepatocyte mass. 99mTc-GSA scintigraphy and hepatic SPECT therefore provide information regarding global and regional reserve hepatic function.
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Case Reports |
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Pan XQ, Darby C, Indik ZK, Schreiber AD. Activation of three classes of nonreceptor tyrosine kinases following Fc gamma receptor crosslinking in human monocytes. Clin Immunol 1999; 90:55-64. [PMID: 9884353 DOI: 10.1006/clim.1998.4644] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fc gamma receptors on monocytes/macrophages play an important role in both host defense and autoimmune disorders. Fc gamma receptor signaling can lead to such downstream events as phagocytosis and the release of intracellular cytokines and reactive oxygen species. Freshly isolated human monocytes express two major classes of Fc gamma receptor proteins, Fc gamma RI (CD64) and Fc gamma RII (CD32). Crosslinking of Fc gamma RI and Fc gamma RII gives rise to rapid and transient phosphorylation of multiple monocyte intracellular proteins including proteins of 40, 68-72, 75-85, 95, and 115-165 kDa. A 72-kDa protein was earlier identified as the tyrosine kinase Syk. Here we identify one of the proteins in the 115- to 165-kDa cluster as FAK, a protein tyrosine kinase localized to focal adhesions. A 68-kDa phosphoprotein was identified as paxillin, a cytoskeleton associated substrate for tyrosine kinases, and a 95-kDa protein was found to be the proto-oncogene product Vav. The Src family protein tyrosine kinase Fgr (p58) also displayed enhanced tyrosine phosphorylation after Fc gamma RI and Fc gamma RII crosslinking. Although Fc gamma RIIA utilizes tyrosines within its own cytoplasmic domain for signaling while Fc gamma RI utilizes the cytoplasmic tyrosines of its associated gamma subunit, our results indicate sharing of several proteins for signaling in monocytes by these Fc receptors. These molecules include three distinct classes of tyrosine kinases, Syk, FAK, and Fgr, and the functionally diverse proteins Vav and paxillin.
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Laine RM, Marchal JC, Sun HP, Pan XQ. Nano-alpha-Al2O3 by liquid-feed flame spray pyrolysis. NATURE MATERIALS 2006; 5:710-2. [PMID: 16892048 DOI: 10.1038/nmat1711] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2005] [Accepted: 06/29/2006] [Indexed: 05/11/2023]
Abstract
Nanometre-sized particles of transition (t)-aluminas are important for the fabrication of high-quality alumina ceramics. Multiple tons are produced each year using a variety of gas-phase processes. The nanoparticles produced by these methods consist mainly of the undesired delta phase with some gamma- and theta-Al(2)O(3). Nano-t-aluminas should provide access to dense nano/submicrometre-grained alpha-Al(2)O(3) shapes offering significant advantages over micrometre-grained shapes. Unfortunately, polymorphism coupled with the high activation energy for nucleating alpha-Al(2)O(3) greatly impedes efforts to process dense alpha-Al(2)O(3) with controlled grain sizes, especially for submicrometre materials. Typically alpha-Al(2)O(3) nucleation within t-aluminas is sporadic rather than uniform, leading to exaggerated grain growth and vermicular microstructures without full densification (5). Thus, production of quantities of nano-alpha-Al(2)O(3) from multiple nano-t-aluminas for seeding or direct processing of alpha-Al(2)O(3) monoliths could greatly change how alpha-Al(2)O(3) components are processed. We report here that liquid-feed flame spray pyrolysis of nano-t-aluminas converts them to dispersible 30-80 nm alpha-Al(2)O(3) powders (50-85% phase transformed). Surprisingly, the powder surfaces are fully dehydrated. These powders pressureless sinter to more than 99.5% dense alpha-Al(2)O(3) with final grain sizes < or =500 nm without sintering aids.
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Kim MK, Pan XQ, Huang ZY, Hunter S, Hwang PH, Indik ZK, Schreiber AD. Fc gamma receptors differ in their structural requirements for interaction with the tyrosine kinase Syk in the initial steps of signaling for phagocytosis. Clin Immunol 2001; 98:125-32. [PMID: 11141335 DOI: 10.1006/clim.2000.4955] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Receptors for the constant region of IgG, Fc gamma receptors, are expressed on the surface of hematopoietic cells, where they mediate signaling events, such as phagocytosis, essential for host defense. Fc gamma receptors also play a role in the pathophysiology of autoimmune diseases. We have demonstrated that members of each of the three classes of human Fc gamma receptors, Fc gamma RI, Fc gamma RII, and Fc gamma RIII, mediate phagocytosis, but that important differences exist in their requirements for phagocytic signaling. For example, the Fc gamma receptors Fc gamma RI and Fc gamma RIIIA induce signaling largely by association with a gamma subunit containing a conserved cytoplasmic motif (ITAM) whose tyrosines are phosphorylated following receptor stimulation. Fc gamma RIIA contains a similar motif in its own cytoplasmic domain and does not require the gamma chain for phagocytic signaling. The tyrosine kinase Syk associates with the cytoplasmic domain of both the Fc gamma receptor gamma chain and Fc gamma RIIA and is required for phagocytosis by both Fc gamma receptor systems. To elucidate the differences in phagocytic signaling by the gamma chain and Fc gamma RIIA, we investigated the requirements for Fc gamma receptor/Syk co-immunoprecipitation, tyrosine phosphorylation, and phagocytosis. Both Fc gamma RIIA and the human gamma chain contain a tyrosine seven amino acids upstream of the ITAM motif. We observed that the upstream tyrosine plays a role in Fc gamma RIIA phagocytic signaling but is not involved in phagocytic signaling by the human gamma chain. Our data also indicate that the two ITAM tyrosines of the human gamma chain and Fc gamma RIIA do not contribute equally to Fc gamma receptor association with Syk kinase and phagocytic signaling. The data indicate that the carboxy-terminal tyrosine of the receptor cytoplasmic domain is especially important both for the interaction with Syk kinase and for phagocytosis. Elucidating such differences in gamma chain and Fc gamma RIIA signaling may be valuable in designing strategies for therapeutic intervention in hematopoietic and immunological disorders.
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Jang HW, Baek SH, Ortiz D, Folkman CM, Das RR, Chu YH, Shafer P, Zhang JX, Choudhury S, Vaithyanathan V, Chen YB, Felker DA, Biegalski MD, Rzchowski MS, Pan XQ, Schlom DG, Chen LQ, Ramesh R, Eom CB. Strain-induced polarization rotation in epitaxial (001) BiFeO3 thin films. PHYSICAL REVIEW LETTERS 2008; 101:107602. [PMID: 18851256 DOI: 10.1103/physrevlett.101.107602] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Indexed: 05/12/2023]
Abstract
Direct measurement of the remanent polarization of high quality (001)-oriented epitaxial BiFeO3 thin films shows a strong strain dependence, even larger than conventional (001)-oriented PbTiO3 films. Thermodynamic analysis reveals that a strain-induced polarization rotation mechanism is responsible for the large change in the out-of-plane polarization of (001) BiFeO3 with biaxial strain while the spontaneous polarization itself remains almost constant.
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Lee S, Jiang J, Zhang Y, Bark CW, Weiss JD, Tarantini C, Nelson CT, Jang HW, Folkman CM, Baek SH, Polyanskii A, Abraimov D, Yamamoto A, Park JW, Pan XQ, Hellstrom EE, Larbalestier DC, Eom CB. Template engineering of Co-doped BaFe2As2 single-crystal thin films. NATURE MATERIALS 2010; 9:397-402. [PMID: 20190768 DOI: 10.1038/nmat2721] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Accepted: 02/05/2010] [Indexed: 05/28/2023]
Abstract
Understanding new superconductors requires high-quality epitaxial thin films to explore intrinsic electromagnetic properties and evaluate device applications. So far, superconducting properties of ferropnictide thin films seem compromised by imperfect epitaxial growth and poor connectivity of the superconducting phase. Here we report new template engineering using single-crystal intermediate layers of (001) SrTiO(3) and BaTiO(3) grown on various perovskite substrates that enables genuine epitaxial films of Co-doped BaFe(2)As(2) with a high transition temperature (T(c,rho=0) of 21.5 K, where rho=resistivity), a small transition width (DeltaT(c)=1.3 K), a superior critical current density J(c) of 4.5 MA cm(-2) (4.2 K) and strong c-axis flux pinning. Implementing SrTiO(3) or BaTiO(3) templates to match the alkaline-earth layer in the Ba-122 with the alkaline-earth/oxygen layer in the templates opens new avenues for epitaxial growth of ferropnictides on multifunctional single-crystal substrates. Beyond superconductors, it provides a framework for growing heteroepitaxial intermetallic compounds on various substrates by matching interfacial layers between templates and thin-film overlayers.
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Beekman C, Siemons W, Ward TZ, Chi M, Howe J, Biegalski MD, Balke N, Maksymovych P, Farrar AK, Romero JB, Gao P, Pan XQ, Tenne DA, Christen HM. Phase transitions, phase coexistence, and piezoelectric switching behavior in highly strained BiFeO(3) films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:5561-7. [PMID: 23847158 DOI: 10.1002/adma.201302066] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Indexed: 05/12/2023]
Abstract
Highly strained BiFeO3 films transition into a true tetragonal state at 430 °C but remain polar to much higher temperatures (∼800 °C). Piezoelectric switching is only possible up to 300 °C, i.e., at temperatures for which strain stabilizes the stripe-like coexistence of multiple polymorphs.
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Lee S, Tarantini C, Gao P, Jiang J, Weiss JD, Kametani F, Folkman CM, Zhang Y, Pan XQ, Hellstrom EE, Larbalestier DC, Eom CB. Artificially engineered superlattices of pnictide superconductors. NATURE MATERIALS 2013; 12:392-396. [PMID: 23455850 DOI: 10.1038/nmat3575] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 01/25/2013] [Indexed: 06/01/2023]
Abstract
Significant progress has been achieved in fabricating high-quality bulk and thin-film iron-based superconductors. In particular, artificial layered pnictide superlattices offer the possibility of tailoring the superconducting properties and understanding the mechanism of the superconductivity itself. For high-field applications, large critical current densities (J(c)) and irreversibility fields (H(irr)) are indispensable along all crystal directions. On the other hand, the development of superconducting devices such as tunnel junctions requires multilayered heterostructures. Here we show that artificially engineered undoped Ba-122/Co-doped Ba-122 compositionally modulated superlattices produce ab-aligned nanoparticle arrays. These layer and self-assemble along c-axis-aligned defects, and combine to produce very large J(c) and H(irr) enhancements over a wide angular range. We also demonstrate a structurally modulated SrTiO3(STO)/Co-doped Ba-122 superlattice with sharp interfaces. Success in superlattice fabrication involving pnictides will aid the progress of heterostructured systems exhibiting new interfacial phenomena and device applications.
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Zhu KM, He SP, Pan XQ, Zheng XR, Gu YA. The relation of urinary cations to blood pressure in boys aged seven to eight years. Am J Epidemiol 1987; 126:658-63. [PMID: 3631055 DOI: 10.1093/oxfordjournals.aje.a114705] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
A study on the relation between urinary cations and blood pressure was conducted in Wuhan, China. A total of 148 boys aged 7-8 years entered the study from November 23, 1984, to January 13, 1985. Seven consecutive 24-hour urine specimens were collected and blood pressure was measured on the seven successive days corresponding to urine collection. The multiple regression showed that none of the sodium, potassium, calcium, and magnesium cations was statistically significantly related to blood pressure. However, the ratio of sodium/calcium or potassium/calcium in the urine was positively correlated with systolic pressure in multivariate analysis. The results suggest that there may be a complex interaction between sodium and calcium in their effects on blood pressure, and genetic background might have some influences on the sodium/calcium (or potassium/calcium)-blood pressure relation in the 7-8-year-old boys in the study.
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Scheinberg DA, Pan XQ, Wilsnack R, Strand M. Rapid screening of monoclonal antibodies: new 'microstick' radioimmunoassay. J Immunol Methods 1983; 58:285-92. [PMID: 6833770 DOI: 10.1016/0022-1759(83)90356-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
A new system for assaying monoclonal antibodies consisting of an 8 x 12 array of sticks which fits into a 96-well microtiter plate is described. Tests using virus specific monoclonal antibodies and virus proteins demonstrated sensitivity equivalent to the conventional microtiter plate assay. Antibody production, antigen specific antibody, and immunoglobulin isotypes could be measured under sterile conditions directly in the original fusion mixture wells and with much greater rapidity than with the microtiter plate assay.
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Wang Y, Pan XQ, Lheureux F, Georges E. Overexpression of a 40-kDa protein in human multidrug resistant cells. Biochem Biophys Res Commun 1997; 236:483-8. [PMID: 9240465 DOI: 10.1006/bbrc.1997.6991] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The use of anticancer drugs in the chemotherapeutic treatment of cancer patients frequently results in the emergence of drug resistant tumors. Selection of tumor cell lines in vitro has led to the identification of several proteins that mediate drug resistance to anticancer drugs. In this study, an immuno-dot blot method was used to isolate a monoclonal antibody (IPM96) which recognized a 40 kDa protein (or P-40) co-expressed with P-glycoprotein and MRP in several multidrug resistant cell lines (MCF-7/Adr, SKOV/VLB1.0, H69/Adr, and HL60/AR). Furthermore, P-40 levels dropped significantly in one revertant cell line (H69/PR) derived from H69/AR cells. Interestingly, the expression of P-40 was also higher in two tumor cell lines (SKTax6a and A2780CP) that were selected with paclitaxel or cisplatin but do not express P-gp or MRP. Immuno-fluorescence staining of cells with IPM96 showed both membrane and cytoplasmic staining. These results were confirmed by Western blot analysis of different subcellular fractions from MCF-7/Adr cells. The membrane bound P-40 was resistant to extraction with high salt, chelating agents, and denaturing agents, but was solubilized with 10 mM CHAPS. Taken together, the overexpression of P-40 in multidrug resistant cells has not been previously determined and therefore could be important in the expression of the drug resistance phenotype.
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Su J, Qin Y, Shen C, Gao Y, Pan EC, Pan XQ, Tao R, Zhang YQ, Wu M. [Association between smoking/smoking cessation and glycemic control in male patients with type 2 diabetes]. ZHONGHUA LIU XING BING XUE ZA ZHI = ZHONGHUA LIUXINGBINGXUE ZAZHI 2018; 38:1454-1459. [PMID: 29141328 DOI: 10.3760/cma.j.issn.0254-6450.2017.11.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Objective: To explore the association of smoking and smoking cessation with glycemic control in male patients with type 2 diabetes. Methods: From December 2013 to January 2014, a total of 7 763 male patients with type 2 diabetes, who received national basic public health service in Changshu county of Suzhou city, Huai'an and Qinghe districts of Huai'an city, Jiangsu province, were recruited by cluster sampling. Questionnaire survey and anthropometric measurements were conducted, and fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) levels were measured. Multiple linear regression model was used to evaluate the association of smoking and smoking cessation with glycemic control. Results: The prevalence of current smoking was 45.5% in male patients with type 2 diabetes. The levels of FPG and HbA1c increased with number of cigarettes smoked per day compared with non-smokers (P<0.001). Among patients with drug treatment, the average increase of HbA1c level in current smokers with smoking duration ≥30 years and smoking index ≥40 pack-years were 0.27% (95%CI: 0.05%-0.49%) and 0.38% (95%CI: 0.23%-0.53%), respectively. FPG and HbA1c level decreased obviously with smoking cessation years among former smokers (P<0.05). Among the patients receiving no drug treatment, no dose-response relationships were observed between smoking duration, smoking cessation years and levels of FPG and HbA1c. Conclusion: Cigarette smoking was negatively related with glycemic control in male type 2 diabetes patients, especially in patients with drug treatment. Smoking cessation may be beneficial for glycemic control. Smoking cessation should be encouraged for diabetes patients as early as possible.
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