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Low-temperature magnetic properties of horse spleen ferritin

chinese science Bulletin 2010年第27期55卷 3174-3180页

作者： tian lanxiang 1,2,cao changqian 1,2,liu qingsong 1,2 &pan yongxin 1,2 1key laboratory of the earth’s deep interior,institute of geology and geophysics,chinese academy of sciences,beijing 10002.,china 2Franco-chinese Biomineralization and Nano-structures laboratory,beijing 10002.,china key laboratory of the earth’s deep interior Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China Franco-chinese Biomineralization and Nano-structures laboratory Beijing China

The magnetic properties of the antiferromagnetic cores in ferritin are of importance in the construction and improvement of ferritin-based magnetic resonance imaging systems and their application to environmental *** this study,we carry out integrated magnetic and transmission electron microscopy analyses of horse spleen ferritin(HosF)to understand the relationships between the magnetic behavior of HosF and temperature,applied field and grain-size *** R-value from the Wohlfarth-Cisowski test for the investigated sample at 5 K was 0.46,indicating very weak magnetostatic interactions among the nanoparticles of *** nanoparticles of HosF show superparamagnetic properties at room temperature,while below the blocking temperature of Tb≈12 K it has a net magnetic moment that comes from the uncompensated spins of the nanoparticle surface or *** thermal relaxation process of HosF follows the Néel-Arrhenius *** low-temperature AC susceptibility data,we calculated the effective magnetic anisotropy energy Ea=(5.52±0.16)×10-21 J;the effective magnetic anisotropy energy constant Keff=(4.65±0.14)×10 4 J/m3 and the pre-exponential frequency factor f0 =(4.52±2.93)×1011 *** values are useful in understanding the magnetic behavior of the antiferromagnetic nanoparticles and their potential application in biomedical technology.

关键词：马脾铁蛋白低温度磁性质透射电子显微镜磁各向异性常数纳米粒子生物医学技术交流磁化率

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DMTB:A comprehensive online resource of 16s rRNA genes,ecological metadata,oligonucleotides,and magnetic properties of magnetotactic bacteria

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chinese science Bulletin 2011年第6期56卷 476-478页

作者： LIN Wei1,2, LI Bi1,2 & pan yongxin1,2 1 Paleomagnetism and Geochronology laboratory, key laboratory of the earth’s deep interior, institute of geology and geophysics, chinese academy of sciences, beijing 10002., china 2 France-china Bio-Mineralization and Nano-structures laboratory, institute of geology and geophysics, chinese academy of sciences, beijing 10002., china Paleomagnetism and Geochronology laboratory Key Laboratory of the Earth’s Deep Interior Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China France-china Bio-Mineralization and Nano-structures laboratory Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China

Magnetotactic bacteria (MTB) are of interest in microbiology, biomineralization, advanced magnetic materials, and bio-geo-sciences because of their ability to form highly ordered intracellular magnetic minerals. Great strides for MTB studies have been made in the past four decades. In this paper we complied the first internet-accessible database for MTB, Database of Magnestotactic Bacteria (DMTB). It contains information of 16s rRNA gene sequences, corresponding ecological metadata, oligonucleotides, and magnetic properties of MTB. The comprehensive information contained in DMTB will provide a very useful data resource for researchers from different disciplines. The website of DMTB is at http://***/.

关键词： rRNA基因序列趋磁细菌 16s 网上资源寡核苷酸磁学性质生态磁性材料

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Magnetic characterization of noninteracting,randomly oriented,nanometer-scale ferrimagnetic particles

Magnetic characterization of noninteracting,randomly oriente...

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中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： changqian cao,lanxiang tian,qingsong liu,Weifeng liu,Guanjun Chen, and yongxin pan 1 Paleomagnetism and Geochronology laboratory,key laboratory of the earth’s deep interior,institute of geology and geophysics,chinese academy of sciences,beijing,china. 2 Also at France-china Bio-Mineralization and Nano-structures laboratory,institute of geology and geophysics,chinese academy of sciences,beijing,china. 3 Also at Graduate University of chinese academy of sciences,beijing, china. 4 state key laboratory of Microbial Technology,school of Life sciences,shandong University,Jinan,china.

[1]studying the magnetic properties of ultrafine nanometer-scale femmagnetic particles (<10 nm)is vital to our understanding of superparamagnetism and its applications to environmental magnetism,biogeomagnetism,iron b...

[1]studying the magnetic properties of ultrafine nanometer-scale femmagnetic particles (10 nm)is vital to our understanding of superparamagnetism and its applications to environmental magnetism,biogeomagnetism,iron biomineralization,and biomedical ***,magnetic properties of the ultrafine nanometer-sized femmagnetic grains are very poorly constrained because of ambiguities caused by particle magnetostatic interactions and unknown size *** resolve these problems,we synthesized magnetoferritins using the recombinant human H chain ferritin(HFn). These femmagnetic HFn were further purified through size exclusion chromatography to obtain monodispersed ferrimagnetic *** electron microscopy revealed that the purified ferrimagnetic HFn are monodispersed and each consists of an iron oxide core(magnetite or maghemite)with an average core diameter of 3.9±1.1 nm imbedded in an intact protein *** R value of the Wohlfarth-Cisowski test measured at 5 K is 0.5,indicating no magnetostatic *** saturation isothermal remanent magnetization acquired at 5 K decreased rapidly with increasing temperature with a median unblocking temperature of 8.2 *** preexponential frequency factor f determined by AC susceptibility is(9.2±7.9)×*** extrapolated M/M and B/B at 0 K are 0.5 and 1.12,respectively,suggesting that the ferrimagnetic HFn cores are dominated by uniaxial *** calculated effective magnetic anisotropy energy constant K=1.2×10 J/m,which is larger than previously reported values for bulk magnetite and/or maghemite or magnetoferritin and is attributed to the effect of surface *** data provide useful insights into superparamagnetism as well as biomineralization of ultrafine ferrimagnetic particles.

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Low-temperature magnetic properties of horse spleen ferritin

Low-temperature magnetic properties of horse spleen ferritin

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中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： tian lanxiang~(1,2),cao changqian~(1,2),liu qingsong~(1,2) & pan yongxin~(1,2*) 1 key laboratory of the earth’s deep interior,institute of geology and geophysics,chinese academy of sciences,beijing 10002.,china 2 Franco-chinese Biomineralization and Nano-structures laboratory,beijing 10002.,china

The magnetic properties of the antiferromagnetic cores in ferritin are of importance in the construction and improvement of ferritin -based magnetic resonance imaging systems and their application to environmental *** this study,we carry out integrated magnetic and transmission electron microscopy analyses of horse spleen ferritin(HosF)to understand the relationships between the magnetic behavior of HosF and temperature,applied field and grain-size *** R-value from the Woh1-farth -Cisowski test for the investigated sample at 5 K was 0.46,indicating very weak magnetostatic interactions among the nanoparticles of *** nanoparticles of HosF show superparamagnetic properties at room temperature,while below the blocking temperature of T≈12 K it has a net magnetic moment that comes from the uncompensated spins of the nanoparticle surface or *** thermal relaxation process of HosF follows the Neel-Arrhenius *** low-temperature AC susceptibility data,we calculated the effective magnetic anisotropy energy E=(5.52±0.16)×l0J;the effective magnetic anisotropy energy constant K=(4.65±0.14)×l0 J/m and the pre-exponential frequency factor f=(4.52±2.93)×*** values are useful in understanding the magnetic behavior of the antiferromagnetic nanoparticles and their potential application in biomedical technology.

关键词： horse spleen ferritin superparamagnetic low temperature magnetic properties pre-exponential frequency factor

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Temporal variation of magnetotactic bacterial communities in two freshwater sediment microcosms

Temporal variation of magnetotactic bacterial communities in...

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中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： Wei Lin~(1,2) & yongxin pan~1 1 Biogeomagnetism Group,Paleomagnetism and Geochronology laboratory,key laboratory of the earth’s deep interior,institute of geology and geophysics,chinese academy of sciences,beijing,china and 2 Graduate University of chinese academy of sciences,beijing,china

Magnetotactic bacteria(MTB),which can mineralize nanosized magnetite or greigite crystals within cells,play important roles in biogeochemical processes,for example iron and sulfur cycling,and depositional remanent magnetization *** decades of research,the knowledge of MTB distribution and ecology is still *** the present study,we investigated the temporal variation of MTB communities in freshwater sediment microcosms based on 16s rRNA genes and unifrac *** microcosms(MY8 and MY11)collected from two separate sites in Lake Miyun(beijing,china)were *** majority of retrieved sequences belonged to alphaproteobacterial magnetotactic cocci in both microcosms(representing 64.29%of clones from MY8 and 100%of clones from MY11),whereas so-called ’Magnetobacterium bavaricum’-like MTB affiliated with in Nitrospira phylum were exclusively found in microcosm *** a 3-month period,the temporal variation of MTB communities was evident in both *** addition,the phylogenetic discrepancy of MTB communities between two microcosms is more prominent than that of the same microcosm at different times,implying adaptation of MTB phylogenetic lineages to specific *** the physical-chemical parameters measured,a strong correlation was shown between nitrate and the main genetic variability of MTB communities,indicating that nitrate may influence the occurrence of MTB phylogenetic lineages in natural environments.

关键词： magnetotactic bacteria physical-chemical parameters 16s rRNA gene unifrac statistical analysis

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Bat Head Contains soft Magnetic Particles:Evidence From Magnetism

Bat Head Contains Soft Magnetic Particles:Evidence From Magn...

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中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： lanxiang tian,~1 Wei Lin,~1shuyi Zhang,~2and yongxin pan~(1*) 1 Biogeomagnetism Group,Paleomagnetism and Geochronology laboratory, key laboratory of the earth’s deep interior,institute of geology and geophysics, chinese academy of sciences,beijing,china 2 school of Life sciences,East china Normal University,shanghai,china

Recent behavioral observations have indicated that bats can sense the earth’s magnetic field. To unravel the magnetoreception mechanism,the present study has utilized magnetic measurements on three migratory species(Miniopterus fuliginosus,Chaerephon plicata,and Nyctalus plancyi)and three non-migratory species(Hipposideros armiger,Myotis ricketti,and Rhinolophus ferrumequinum). Room temperature isothermal remanent magnetization acquisition and alternating-field demagnetization showed that the bats’ heads contain soft magnetic *** analyses indicated that the saturation isothermal remanent magnetization of brains(sIRM)of migratory species is higher than those of non-migratory ***,the sIRMof migratory bats is greater than their ***-temperature magnetic measurements suggested that the magnetic particles are likely magnetite(FeO).This new evidence supports the assumption that some bats use magnetite particles for sensing and orientation in the earth’s magnetic field.

关键词： bat magnetoreceptor magnetic measurements migratory non-migratory

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DMTB:A comprehensive online resource of 16s rRNA genes,ecological metadata,oligonucleotides,and magnetic properties of magnetotactic bacteria

DMTB:A comprehensive online resource of 16S rRNA genes,ecolo...

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中国科学院地质与地球物理研究所第11届（2011年度）学术年会

作者： LIN Wei~(1,2),LI Bi~(1,2) & pan yongxin~(1,2) 1 Paleomagnetism and Geochronology laboratory,key laboratory of the earth’s deep interior,institute of geology and geophysics,chinese academy of sciences,beijing 10002.,china 2 France-china Bio-Mineralization and Nano-structures laboratory,institute of geology and geophysics,chinese academy of sciences,beijing 10002.,china

Magnetotactic bacteria(MTB) are of interest in microbiology,biomineralization,advanced magnetic materials,and bio-geo-sciences because of their ability to form highly ordered intracellular magnetic *** strides for MTB studies have been made in the past four *** this paper we complied the first internet-accessible database for MTB,Database of Magnestotactic Bacteria(DMTB).It contains information of 16s rRNA gene sequences,corresponding ecological metadata,oligonucleotides, and magnetic properties of *** comprehensive information contained in DMTB will provide a very useful data resource for researchers from different *** website of DMTB is at http://***/.

关键词： magnetotactic bacteria biomineralization database

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snapping magnetosome chains by asymmetric cell division in magnetotactic bacteria

Snapping magnetosome chains by asymmetric cell division in m...

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中国科学院地质与地球物理研究所第11届（2011年度）学术年会

作者： Wei Lin~(1,2) and yongxin pan~(1,2*) 1 Biogeomagnetism Group,Paleomagnetism and Geochronology laboratory,key laboratory of the earth’s deep interior,institute of geology and geophysics,chinese academy of sciences,beijing 10002.,china. 2 France-china Bio-Mineralization and Nano-structures laboratory,chinese academy of sciences,beijing 10002.,china.

summary The mechanism by which prokaryotic cells organize and segregate their intracellular organelles during cell division has recently been the subject of substantial *** other microorganisms,magnetotactic bacteria(MTB) form internal magnets(known as mag-netosome chain) for magnetic orientation,and thus face an additional challenge of dividing and equiparti-tioning this magnetic receptor to their daughter cells. Although MTB have been investigated more than four decades,it is only recently that the basic mechanism of how MTB divide and segregate their magnetic organelles has been *** this issue of Molecular Microbiology,the cell cycle of the model magnetotactic bacterium,Magnetospirillum gryph-iswaldense is characterized by Katzmann and *** authors have found that ***-iswaldense undergoes an asymmetric cell division along two planes.A novel wedge-like type of cellular constriction is observed before separation of daughter cells and magnetosome chains,which is assumed to help cell cope with the magnetic force within the mag-netosome *** data shows that the magneto- some chain becomes actively recruited to the cellular division site,in agreement with the previous suggestions described by staniland et al.(2010),and the actin-like protein MamK is likely involved in this fast polar-to-midcell *** the use of cryo-electron tomography,an arc-shaped Z ring is observed near the division site,which is assumed to trigger the asymmetric septation of cell and magneto-some chain.

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Magnetic properties related to thermal treatment of pyrite

Magnetic properties related to thermal treatment of pyrite

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中国科学院地质与地球物理研究所2008学术年会

作者： WANG Lei~(1,2),pan yongxin~(1,3+),LI JinHua~(1,2) & QIN HuaFeng~(1,2) 1 Paleomagnetism and Geochronology laboratory(sKL-LE),institute of geology and geophysics,chinese academy of sciences, beijing 10002.,china 2 Graduate University,chinese academy of sciences,beijing 100049,china 3 key laboratory of the study of earth’s deep interior,institute of geology and geophysics,chinese academy of sciences,beijing 10002.,china

Detailed rock magnetic experiments were conducted on high-purity natural crystalline pyrite and its products of thermal treatments in both argon and air *** argon atmosphere(reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite;the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of～20 and～30 mT,respectively. Whereas in air,the pyrite is ultimately oxidized to *** order reversal curve(FORC) diagram of the end product shows that the remanence coercivity of hematite is up to～1400 *** corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite→pyrrhotite→magnetite→*** results are helpful for understanding of sedimentary magnetism, secondary chemical remanence and meteorolite magnetic properties.

关键词： pyrite pyrrhotite magnetite hematite thermal alteration rock-magnetic properties

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New 40Ar/39Ar dating results from the shanwang Basin,eastern china:Constraints on the age of the shanwang Formation and associated biota

New 40Ar/39Ar dating results from the Shanwang Basin,eastern...

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中国科学院地质与地球物理研究所第11届（2011年度）学术年会

作者： Huaiyu He~(a,*),Chenglong Deng~b,yongxin pan~a,Tao Deng~c,Zhaohua Luo~d,Jimin sunb,Rixiang Zhu~b a key laboratory of the earth’s deep interior,institute of geology and geophysics,chinese academy of sciences,beijing 10002.,china b state key laboratory of Lithospheric Evolution,institute of geology and geophysics,chinese academy of sciences,beijing 10002.,china c institute of Vertebrate Paleontology and Paleoanthropology,chinese academy of sciences,beijing 100044,china d china University of Geosciences,beijing 100083,china

The fluvio-lacustrine sequence of the shanwang Basin,eastern china,preserves a rich and important terrestrial fossil fauna and flora;the exceptional preservation of these fossils reveals the dynamics of ancient mammalian ecosystems and plant ***,the timing of this sedimentary sequence has been the subject of debate for *** we contribute to this debate by presenting the detailed results of Ar/Ar analysis of the basalts above,below,and within the shanwang *** dates place stringent constraints on the age of shanwang Formation and associated ***/Ar ages obtained from basalts of the Niushan and Yaoshan Formations,which underlie and overlie the shanwang Formation, are 21.0±2.5 Ma(2σ,full external error) and 17.3±1.5 Ma(2σ,full external error),respectively. The Ar/Ar age of the basalt in the shanwang Formation is 17-18 *** the age constraints of the basalts of the Yaoshan and shanwang Formations,the age of the shanwang biota is estimated to be ca.17 Ma,late Burdigalian of the Early Miocene,indicating that the deposition of this fauna coincided with the onset of the mid-Miocene Climatic *** results provide new age constraints on the shanwang mammal fauna,and independently support interpretations that this fauna can be assigned to chronozone MN4,and correlated with middle Orleanian of the European Land Mammal *** to late Hemingfordian of the North American Land Mammal *** diversity of the shanwang Formation could reflect the global-scale mid-Miocene Climatic Optimum.

关键词： 40Ar/39Ar dating Geochronology shanwang Formation shanwang biota Miocene

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