The International Conference on Neutron and x-ray Scattering icnx2007



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The International Conference on Neutron and X-Ray Scattering - ICNX2007

Neutron and X-Ray Scattering in Materials Science and Biology

Indonesia, July 23 – 31, 2007








PLM01
Application of X-ray and Neutron Scattering Techniques in Materials Research: Lithium Batteries and Electronic Ceramics
A. R. West1

1 University of Sheffield, Department of Engineering Materials, Sir Robert Hadfield Building, Mappin

Street, Sheffield, S1 3JD. UK

X-ray and neutron powder diffraction provide complementary information on the structures of inorganic complex oxides, primarily because of the different dependence of atomic scattering power, or scattering length, on atomic number. Neutron diffraction is particularly useful for characterising novel lithium transition metal oxides which have applications in prototype advanced lithium battery systems. Thus, it is possible to establish conduction pathways for mobile Li+ ions and to distinguish between transition metal ions in ordered spinel structures such as Li2NiMn3O8, which has a charge-discharge potential of 4.7V. An additional feature of such materials is oxygen non-stoichiometry in which their oxygen content depends on sample preparation conditions and temperature. This oxygen non-stoichiometry may be analysed by thermogravimetry and the transition metal oxidation states determined, in the solid state, by the X-ray absorption technique, XANES. Structural changes as a function of temperature may be followed by high temperature diffraction methods and as a function of lithium content during charging/discharging of lithium batteries by in situ synchrotron XRD. A range of examples of the applications of these techniques will be presented.


References

1. Inorganic functional materials: Optimization of properties by structural and compositional control, A R West, The Chemical Record, 6, 206-216 (2006).

2. Crystallography of Ni-doped Zn7Sb2O12 and phase equilibria in the system ZnO-Sb2O5-NiO, R Harrington, G C Miles and A R West, J Eur Ceram Soc, 26, 2307-2311 (2006).

3. Structural characterisation of REBaCo2O6-δ phases (RE-Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho), P S Anderson, C A Kirk, J Knudsen, I M Reaney and A R West, Solid State Sciences, 7, 1149-1156 (2003).

4. Temperature-dependent crystal structure of ferroelectric Ba2LaTi2Nb3O15, G C Miles, M C Stennett, I M Reaney and A R West, J Mater Chem, 15, 798-802 (2005).

5. Oxygen content and electrochemical activity of LiCoMnO4-δ, D Pasero, S de Souza, N Reeves and A R West, J Mat Chem, 15, 4435-4440 (2005).


Keywords: powder diffraction, synchrotron, lithium battery
Corresponding author: A.R.West@sheffield.ac.uk

PLM02
Early Years of Neutron Scattering and Its Manpower Development in Indonesia
Marsongkohadi1,2

1 Former Professor of Physics, ITB, Bandung, Indonesia

2 Director of Materials Science Research Centre, BATAN, Serpong, Indonesia from 1987 - 1996

In this paper I shall give a short history of development of neutron scattering at the Research Centre for Nuclear Technique (PPTN), in Bandung, and the early development of more advanced facilities at the Neutron Scattering Laboratory (NSL BATAN), Centre for Technology of Nuclear Industrial materials, in Serpong.

The first research reactor in Indonesia was the TRIGA MARK II in Bandung, which became operational in 1965, with a power of 250 KW, upgraded to 1 MW in 1971, and to 2 MW in 2000. The neutron scattering activities were started in 1967, with the design and construction of the first powder diffractometer, and put in operation in 1970. It was followed by the second instrument, the filter spectrometer built in 1975 in collaboration with the Bhabba Atomic Research Centre (BARC), India.

A powder diffractometer for magnetic studies was built in 1980, and finally, a modification of the filter detector spectrometer to measure texture was made in 1986. A brief description of the design and construction of the instruments, and a highlight of some activities at the 30 MW, RSG-GAS reactor in Serpong in choosing a suitable research program, which will be mainly centered around materials testing/characterization, and materials/condensed matter researches has been agreed. Instrument planning and lay-out which were appropriate to carry out the program had been decided. Manpower development for the neutron scattering laboratory is a severe problem. The efforts to overcome this problem have been solved. International Cooperation through workshops and on-the-job trainings also support the supply of qualified manpower.


Keywords: neutron scattering, powder diffractometer, magnetic studies.
Corresponding author:

PLM03
Opportunities for Materials Science and Biological Research at the OPAL Research Reactor
S. J. Kennedy1

1 Bragg Institute, ANSTO, Australia

Neutron scattering techniques have evolved over more than ½ century into a powerful set of tools for determination of atomic and molecular structures. Modern facilities offer the possibility to determine complex structures over length scales from ~0.1 nm to ~500 nm. They can also provide information on atomic and molecular dynamics, on magnetic interactions and on the location and behaviour of hydrogen in a variety of materials.

The OPAL Research Reactor is a 20 megawatt pool type reactor using low enriched uranium fuel, and cooled by water. OPAL is a multipurpose neutron factory with modern facilities for neutron beam research, radioisotope production and irradiation services. The neutron beam facility has been designed to compete with the best beam facilities in the world. After six years in construction, the reactor and neutron beam facilities are now being commissioned, and we will commence scientific experiments later this year.

The presentation will include an outline of the strengths of neutron scattering and a description of the OPAL research reactor, with particular emphasis on it’s scientific infrastructure. It will also provide an overview of the opportunities for research in materials science and biology that will be possible at OPAL, and mechanisms for accessing the facilities. The discussion will emphasize how researchers from around the world can utilize these exciting new facilities.


Keywords: neutron beam facilities, research reactor, atomic and molecular dynamics.
Corresponding author: sjk@ansto.gov.au

PLM04
J-PARC and Prospective Neutron Science
M. Arai1

1 J-PARC Centre, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan

J-PARC is interdisciplinary facility with high power proton accelerator complex to be completed by 2008 after 7 years construction. Materials-Life Science Facility (MLF) will be very intensive pulsed neutron and muon facility at 1MW of the accelerated proton power. The neutron peak flux will be as high as several hundred times of existing high flux reactors. It is highly expected that new science will be opened up by using MLF. In the presentation I will explain the present status of J-PARC, strategy of user programme and prospective neutron science to be performed with it.


Keywords: proton accelerator, pulsed neutron, muon.
Corresponding author: masatoshi.arai@j-parc.jp

PLM05
Current Status and Future Works of Neutron Scattering Laboratory at BATAN in Serpong
A. Ikram1

1 Center of Technology for Nuclear Industrial Materials, National Nuclear Energy Agency of Indonesia

(BATAN)

Current status of neutron beam instruments using neutrons produced by the Multi Purpose Research Reactor – 30MWth (MPR 30, RSG GA Siwabessy) located in Serpong is presented. Description of the reactor as the neutron source is mentioned briefly. There are six neutron beam tubes coming from the beryllium reflector surrounding half of the reactor core providing neutrons in the experimental hall of the reactor (XHR). Four of them are dedicated to R&D in materials science using neutron scattering techniques. Neutron Radiography Facility (NRF), Triple Axis Spectrometer (TAS) and Residual Stress Measurement (RSM) Diffractometer are installed respectively at beam tubes S2, S4 and S6. The largest neutron beam tube (S5) is exploited to accommodate two neutron guide tubes that transfer the neutrons to a neighbouring building called neutron guide hall (NGH). There are three other neutron beam instruments installed at this building, namely Small Angle Neutron Scattering (SANS) Spectrometer (SMARTer), High Resolution SANS (HRSANS) Spectrometer and High Resolution Powder Diffractometer (HRPD). In the XHR, a Four Circle and Texture Diffractometer (FCD/TD) is attached to one of the neutron guide tubes. These seven instruments were installed to utilize the neutrons for materials and life sciences research, and recently the RSM diffractometer has shown its capabilities in identifying different amount of stress left due to different treatments of welding in fuel cladding, while the SANS spectrometer is now gaining capabilities in identifying different sizes and shapes of macromolecules in polymers, biomacromolecules as well as investigations of magnetic samples. In the mean time, non-destructive tests using the NRF is gathering more confidence from some latest real time measurements eventhough there are still some shortcomings in the components and their alignments. Future works including improvement of each facility and its components, even replacement of some parts are necessary and have to be carried out carefully. A plan for developing a neutron reflectometer at one of the neutron guide in the Neutron Guide Hall is also part of the near future activities.


Keywords: neutron beam instruments, fuel cladding, polymers, biomacromolecules
Corresponding author: nslbatan@centrin.net.id
PLM06
Magnetic Excitations in Transition-metal Oxides Studied by Inelastic Neutron Scattering
M. Braden1

1 Institute of Physics, University of Cologne, Germany

Inelastic neutron scattering using a triple axis spectrometer is a very efficient tool to analyze magnetic excitations. We will discuss several recent experiments on transition-metal oxides where orbital degrees of freedom play an important role. Different kinds of experimental techniques including longitudinal and spherical polarization analysis were used in order to determine not only magnon frequencies but also polarization vectors.

In layered ruthenates bands of different orbital character contribute to the magnetic excitations which are of both, ferromagnetic and antiferromagnetic, character. The orbital dependent magnetic excitations seem to play different roles in the superconducting pairing as well as in the metamagnetism .

In manganates the analysis of the magnon dispersion in the charge and orbital ordered phase yields direct insight into the microscopic coupling of orbital and magnetic degrees of freedom and helps understanding, how the switching between metallic and insulating phases in manganates may occur. In multiferroic TbMnO3 the combination of our polarized neutron scattering results with the infrared measurements identifies a soft collective excitation of hybridized magnon-phonon character.


Keywords: inelastic neutron scattering, magnetic excitations
Corresponding author: braden@ph2.uni-koeln.de

PLM07
Pulsed Neutron Powder Diffraction for Materials Science
T. Kamiyama1,2

1 Materials and Life Science Facility, J-PARC Center, High Energy Accelerator Research Organization,

Tsukuba, Ibaraki 305-0801 JAPAN

The accelerator-based neutron diffraction began in the end of 60’s at Tohoku University which was succeeded by the four spallation neutron facilities with proton accelerators at the High Energy Accelerator Research Organization (Japan), Argonne National Laboratory and Los Alamos Laboratory (USA), and Rutherford Appleton Laboratory (UK). Since then, the next generation source has been pursued for 20 years, and 1MW-class spallation neutron sources will be appeared in about three years at the three parts of the world: Japan, UK and USA. The joint proton accelerator project (J-PARC), a collaborative project between KEK and JAEA, is one of them. The aim of the talk is to describe about J-PARC and the neutron diffractometers being installed at the materials and life science facility of J-PARC.

The materials and life science facility of J-PARC has 23 neutron beam ports and will start delivering the first neutron beam of 25 Hz from 2008 May. Until now, more than 20 proposals have been reviewed by the review committee, and accepted proposal groups have started to get fund. Those proposals include five polycrystalline diffractometers: a super high resolution powder diffractometer (SHRPD), a 0.2 %-resolution powder diffractometer of Ibaraki prefecture (IPD), an engineering diffractometers (Takumi), a high intensity S(Q) diffractometer (VSD), and a high-pressure dedicated diffractometer. SHRPD, Takumi and IPD are being designed and constructed by the joint team of KEK, JAEA and Ibaraki University, whose member are originally from the KEK powder group. These three instruments are expected to start in 2008. VSD is a super high intensity diffractometer with the highest resolution of d/d = 0.3%. VSD can measure rapid time-dependent phenomena of crystalline materials as well as glass, liquid and amorphous materials. The pair distribution function will be routinely obtained by the Fourier transiformation of S(Q) data. Q range of VSD will be as wide as 0.01Å-1 < Q < 100Å-1.

IPD is fully funded by Ibaraki prefecture for the promotion of new industries based on advanced science and technologies. It is for the first time in neutron facilities in Japan that a prefecture owns neutron instruments as well as neutron beam will be provided widely to industrial users. To make it successful, the user system is quite important because those users are expected to use IPD like chemical analyzers in their materials development process. Based on questionnaire data to several hundreds industries, IPD is designed as a versatile diffractometer including texture measurement, small angle scattering and total scattering as well as usual powder diffraction. IPD covers d range 0.15 < d (Å) < 4 with d/d = 0.15 %, and covers 4 < d (Å) < 60 with gradually changing resolution. Q range of IPD will be as wide as 0.01Å-1< Q < 50Å-1 to be utilized for varieties of structures: local structure, nano structure and crystal structure analyses. Typical measuring time for the typical ‘Rietveld-quality’ data is several minutes with the sample size of laboratory X-ray: 0.4 cc.

SHRPD is designed to be the world highest resolution with d/d = 0.03% without sacrificing intensity. The combination of the high quality data from HRPD and their high-precision analysis gives us information on tiny structural changes which have been overlooked. After careful examination with the moderator group five years ago, we have decided to develop a high-resolution & good S/N moderator to achieve the 0.03 % resolution within 100 m flight path. This development was almost successful up to now. Instrumental simulation and radiation analysis were almost completed. The d range 0.5 < d (Å) < 4 with d/d = 0.03 %, and covers 4 < d (Å) < 45 with gradually changing resolution.

Takumi is the first priority instrument in JAEA for stress mapping inside structure materials with the highest resolution of d/d = 0.2% (corresponding to 105 to 106 strain precision). The typical gauge volume will be 1 mm3. JED has transmission radiography detectors to support stress mapping.

Software group is planning so that basic software to cover data acquisition and data treatment should be common. Since 1 Gbyte data are typically obtained for single experiment in an instrument, the basic software is quite important. International TV conference between ISIS, IPNS, SNS has been held every month to exchange information on each development. KEK developed manyo-lib to help basic analysis. Analysis software development including powder diffraction is strongly related with the activity of the software group. However, users of IPD will be from various field of science and their background is different. It should cover wide topics and help both beginners and well-trained users. We have started with neutron intensity database, peak-search software, peak-match software, pattern simulation, whole pattern fitting, PDF and RDF analysis, and now start coding Rietveld software.
Keywords: pulsed neutron, poweder diffractometer, crystalline, glass, amorphous
Corresponding author: takashi.kamiyama@kek.jp
PLM08
Thermal Stress Behavior of Micro- and Nano-Size Aluminum Films
T. Hanabusa1, M. Nishida2, K. Kusaka1

1 Institute of Technology and Science, The University of Tokushima, Tokushima, Japan

2 Department of Mechanical Engineering, Kobe City College of Technology, Kobe, Japan

In-situ observation of thermal stresses in thin films deposited on silicon substrate was made by X-ray and synchrotron radiation. Specimens prepared in this experiment were micro- and nano-size thin aluminum films with and without passivation film. The thickness of the film was 3 µm for micro-size films and 10, 20 and 50 nm for nano-size films. The stress measurement in micro-size films was made by X-ray radiation whereas the measurement of nano-size films was made by synchrotron radiation. Residual stress measurement revealed tensile stresses in all as-deposited films. Thermal stresses were measured in a series of heating- and cooling-stage. Thermal stress behavior of micro-size films revealed hysteresis loop during a heating and cooling process. The width of a hysteresis loop was larger in passivated film than in unpassivated film. No hysteresis loop was observed in nano-size films with SiO2 passivation. Strengthning mechanism in thin films was discussed on a passivation film and a film thickness.


Keywords: Thermal stress, in-situ observation, aluminum film, X-ray measurement, synchrotron radiation
Corresponding author: hanabusa@me.tokushima-u.ac.jp

PLM09
Neutron Reflectometry as a Surface Probe – A Personal Perspective
Z. Tun1

1 Canadian Neutron Beam Centre, National Research Council Canada, Chalk River Laboratories

Chalk River, Ontario, Canada K0J 1J0

Development of neutron reflectometry has enabled neutron scattering laboratories worldwide to make important contributions to the study of surfaces, interfaces and thin-films. As a result, neutron scattering has become an invaluable research tool for the scientific disciplines that did not traditionally use neutrons for research as recently as 20 years ago. At Chalk River (Canada), one discipline with which we have formed a close affiliation is electrochemistry. Our decision in the early 1990s to reach out to this potential user community was based on the fact that Canada has many researchers active in corrosion science. The virtue of this affiliation is best demonstrated in our experiments where reflectometry is performed simultaneously on the sample being investigated with electro-impedance spectroscopy, a standard electrochemical technique. The two methods in combination have led to the results that would have otherwise been missed or wrongly interpreted.


Keywords: neutron reflectometry, electro-impedance spectroscopy, corrosion
Corresponding author: zin.tun@nrc.gc.ca

PLM10
Fractal Structure Investigations with Small-angle Scattering for Dynamical Systems
S. Mazumder

1 Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Bombay 4000 85, India

When a system with continuous symmetry is quenched instantly to a broken symmetry state, new phases of topological defects appears in an otherwise homogeneous medium of continuous symmetry. The further growth of the topological defects are of continuous nature such that the time evolution of the system can be described by Ginzburg-Landau free energy functionals.

The phenomenon of new phase formation is a representative example of first order transition. The phenomenon is fundamental and of immense interest as an example of a highly nonlinear process far from equilibrium. The second phase grows with time and in late stages all domain sizes are much larger than all microscopic lengths. In the large time limit, the new phase forming systems exhibit self-similar growth pattern with dilation symmetry, with time dependent scale, and scaling phenomenon. The phenomenon is indicative of the emergence of a morphological pattern of the domains at earlier times looking statistically similar to a pattern at later times apart from the global change of scale implied by the growth of time dependent characteristic length scale L(t) – a measure of the time dependent domain size of the new phase.

The scaling hypothesis assumes the existence of a single characteristic length scale L(t) such that the domain sizes and their spatial correlation are time invariant when the lengths are scaled by L(t). Quantitatively, for isotropic systems, the equal-time spatio-temporal composition modulation auto-correlation function g(r,t), reflects the way in which the mean density of the medium varies as a function of distance from a given point, should exhibit the scaling form with time-dependent dilation symmetry

g(r,t)=f(r/L(t)) (1)

The scaling function f(r/L(t)) is universal in the sense that it is independent of initial conditions and also on interactions as long as they are short ranged. However, form of f(r/L(t)) depends non-trivially on n, the number of components in the vector order-parameter field exhibiting the scaling behavior, and d, the dimensionality of the system. It is important to note that the scaling hypothesis has not been proved conclusively except for some model systems.

The Fourier transform of g(r,t), the structure factor or scattering function S(q,t) for a d dimensional Euclidean system, obeys simple scaling ansatz at late times,

  S(q,t)=L(t)dF(qL(t)) (2)

Based on some of our recent observations on phase separation of a multicomponent alloy[1-2] and hydration of calcium silicates and calcium sulphates [3-5], we propose to reexamine the extent of validity of scaling laws addressing issues like (i) uniqueness of characteristic length L(t); (ii) the extent of validity of the scaling laws for new phase formation in the case of non-Euclidean fractal systems; (iii) the extent of validity of the scaling laws for multicomponent systems.

The need for investigations examining the extent and the nature of the validity of the scaling laws for confined systems and for systems subjected to random field will also be discussed.


References

[1] S. Mazumder, et al., Phys. Rev. B 60 (1999) 822.

[2] R. Tewari, S. Mazumder, I.S. Batra, G.K. Dey and S. Banerjee, Acta Metall. 48 (2000) 1187.

[3] S. Mazumder, et al., Phys. Rev. Lett 93 (2004) 255704.

[4] S. Mazumder, et al., Phys. Rev. B 72 (2005) 224208.

[5] S. Mazumder, Physica B, 385 (2006) 7 and S. Mazumder et al., Manuscript (in preparation)


Keywords: small angle scattering, phase formation, fractal system
Corresponding author: smazumder@apsara.barc.gov.in

PLT01
Deuterium Labeling and Neutron Scattering for Structural Biology
P. A. Timmins1

1 Large Scale Structures Group, Institut Laue-Langevin, BP156, Grenoble Cedex 9, France

Neutron scattering applications in structural biology are strongly enhanced by deuterium labeling of the aqueous solvent, the macromolecules themselves, or both. In protein crystallography deuteration of the solvent and protein allows a clear visualization of hydrogen sites (deuterium atoms) as well as increasing signal/noise in the diffraction data. This allows crystals as small as 0.1mm3 to be used. In small angle scattering and reflectometry deuteration of the aqueous solvent allows one to manipulate the contrast between different components of complexes such as proteins, nucleic acids or lipids. In the case of multi-protein complexes the in vivo deuteration of individual protein sub-units allows an even more sophisticated contrast variation to be performed.

An outline of in vivo deuteration and contrast variation is given and examples, mainly from crystallography and small angle neutron scattering, are described.
Keywords: protein crystallography, contrast variation, deuteritation
Corresponding author: timmins@ill.fr
PLT02
Membrane Structure Studies by Means of Small-Angle Neutron Scattering (SANS)
R. B. Knott1,2

1 Bragg Institute, ANSTO, Private Mail Bag, Menai NSW 2234, Australia

2 CSIRO Minerals, Box 312, Clayton South VIC 3169, Australia

The basic model for membrane structure – a lipid bilayer with imbedded proteins – was formulated 35 years ago, however the detailed structure is still under active investigation using a variety of physical, chemical and computational techniques. Every biologically active cell is encapsulated by a plasma membrane with most cells also equipped with an extensive intracellular membrane system. The plasma membrane is an important boundary between the cytoplasm of the cell and the external environment, and selectively isolates the cell from that environment. Passive diffusion and/or active transport mechanisms are provided for water, ions, substrates etc. which are vital for cell metabolism and viability. Membranes also facilitate excretion of substances either as useful cellular products or as waste.

Despite their complexity and diverse function, plasma membranes from quite different cells have surprisingly similar compositions. A typical membrane structure consists of a phospholipid bilayer with a number of proteins scattered throughout, along with carbohydrates (glycoproteins), glycolipids and sterols. The plasma membranes of most eukaryotic cells contain approximately equal weights of lipid and protein, which corresponds to about 100 lipid molecules per protein molecule.

Clearly, lipids are a major constituent and the study of their structure and function in isolation provides valuable insight into the more complex intact multicomponent membrane. The membrane bound protein is the other major constituent and is a very active area of research for a number of reasons including the fact that over 60% of modern drugs act on their receptor sites. The interaction between the protein and the supporting lipid bilayer is clearly of major importance.

Neutron scattering is a powerful technique for exploring the structure of membranes, either as reconstituted membranes formed from well characterised lipids, or as intact membranes isolated from selected biological systems. A brief summary of membrane structure will be followed by an outline of the neutron scattering techniques used to understand membrane structure and dynamics. The emphasis will be on the small angle neutron scattering technique since there is a very powerful instrument at Serpong, however brief mention of other techniques will be included to demonstrate how a multidisciplinary approach is usually required.
Keywords: neutron scattering, membrane structure, biology, SANS
Corresponding author: rbk@ansto.gov.au

PLT03
Structural and Functional Characterization of a Glucansucrase (DN-GTF180) from Lactobacillus reuteri 180, a GH Family 70 Enzyme
B. W. Dijkstra1, A. Vujičić-Žagar1, T. Pijning1, S. Kralj2, L. Dijkhuizen2

1 Laboratory of Biophysical Chemistry, University of Groningen, The Netherlands

2 Department of Microbiology, University of Groningen, The Netherlands

Bacterial -Glucans are synthesized by glucansucrase enzymes (glucosyltransferases), using sucrose as substrate. Glucansucrase enzymes cleave the glycosidic bond of their substrate sucrose and couple a glucose unit to a growing glucan (polyglucose) chain (transglucosylation), water (hydrolysis), or to other acceptor substrates (acceptor reaction). Depending on the main glucosidic linkages present in their glucan four different types of -glucans synthesized by lactic acid bacteria are recognized: dextran [-(16)], mutan [-(13)], alternan [-(13) /-(16)] and reuteran [-(14)]1,2.

Due to the vast potential industrial applications of these -glucans, glucansucrases have been extensively studied1,2. To date, 47 different glucansucrases have been classified in Glycoside Hydrolase family 70, but no three-dimensional structure is yet known for them.

In order to investigate the molecular basis of the reaction mechanism of GH70 family enzymes and their linkage type specificity we have purified, crystallized and solved the structure of a 117 kDa N-terminally truncated form of L. reuteri glucansucrase N-GTF1803, synthesizing a glucan containing -(16) and -(13) glucosidic linkages. Also complexes of N-GTF180 with sucrose (substrate) and maltose (acceptor) at 2.3 and 2.0 Å resolution, were solved. Moreover, two native crystal forms, a triclinic and an orthorhombic one (1.6 Å and 2.0 Å resolution, respectively) show that large conformational changes might play an important role in modulating linkage type specificity. The 3D structure revealed that the predicted linear domain organisation of glucansucrases1,2 is erroneous. Instead, a surprising "U-fold” domain structure is observed, in which for 4 of the 5 domains an N- and a C-terminal part of the polypeptide chain combine to form the domain. Our crystallographic results could be fully validated by both biochemical and mutagenesis experiments.

References


  1. Monchois, V., Willemot, R. M. & Monsan, P. Glucansucrases: mechanism of action and structure-function relationships. FEMS Microbiol. Rev. 23, 131-151 (1999).

  2. Van Hijum, S.A.; Kralj, S.; Ozimek, L.K.; Dijkhuizen, L.; Van Geel-Schutten, G.H. Structure-function relationships of glucansucrase and fructansucrase enzymes from lactic acid bacteria (2006) Microbiol. Mol. Biol. Rev. 70, 157-176.

  3. Kralj, S.; Van Geel-Schutten, G.H.; Dondorff, M.M.; Kirsanovs, S.; Van der Maarel, M.J.; Dijkhuizen L. (2004) glucan synthesis in the genus Lactobacillus: isolation and characterization of glucansucrase genes, enzymes and glucan products from six different strains Microbiology, 150, 3681-3690.


Keywords:
Corresponding author: b.w.dijkstra@rug.nl

PLT04
Neutron Protein Crystallography: Beyond the Folding Structure of Biological Macromolecules
N. Niimura1

1 Institute of Applied Beam Science, Ibaraki University, Naka-narusawa, 4-12-1, Hitachi, Ibaraki-ken,

316-8511, Japan

Hydrogen atoms and water molecules around proteins and nucleic acids could play a crucial role in many physiological functions. Neutron diffraction provides an experimental method of directly locating hydrogen atoms.1) Several high-resolution neutron diffractometers, which exploit the neutron image plate, dedicated to biological macromolecules have been constructed to acquire high resolution neutron diffraction data for the location of hydrogen atoms and molecules of hydration in proteins and oligomeric nucleic acids. (a) Since almost all the H atom positions can be identified experimentally, the geometrical details of certain types of H-bonds can be visualized; (b) since the neutron scattering process distinguishes deuterium from hydrogen, information regarding the H/D exchange behavior of proteins can be obtained, and (c) as far as mechanistic implications are concerned, the identification of protonation and deprotonation states of certain important amino acid residues can be carried out. (d) The hydration structure around proteins and the hydration networks around DNA oligomers have been successfully characterized in several outstanding cases.

These will open the new field beyond the folding structure of bio-macromolecules such as:


  1. Recognition of proteins and nucleic acids through the network structure of water molecules surrounding bio-macromolecules, and

  2. The nature of chemical bond in proteins and nucleic acids elucidated by the accumulation of accurate structural information of hydrogen atoms.

Reference:



  1. Nobuo Niimura, Shigeki Arai, Kazuo Kurihara, Toshiyuki Chatake, Ichiro Tanaka, and Robert Bau, Cell. Mol. Life Sci. 62, 285-300 (2006)


Keywords: Neutron protein crystallography, biology, hydrogen, hydration, chemical bond
Corresponding author: niimura@mx.ibaraki.ac.jp

PLT05
Structural Evolution During Protein Unfolding as Induced by Different Methods
V. K. Aswal1, S. Chodankar1, J. Kohlbrecher2, R. Vavrin2 and A. G. Wagh1

1 Solid State Physics Division, Bhabha Atomic Research Center, Mumbai-400 085, India

2 Laboratory for Neutron Scattering, ETH Zurich & Paul Scherrer Institut, CH-5232 Villigen PSI,

Switzerland

Protein folding/unfolding is one of the most complexes, fundamental and universal example of biological self-assembly. We have used small-angle neutron scattering (SANS) to study conformational changes in protein bovine serum albumin (BSA) due to perturbation in its native structure as induced by varying temperature, pressure and in presence of protein denaturating agents urea and surfactant. The mechanism of denaturation is known to be different for these methods. With increase in temperature number of bonds in the protein molecule are weakened, which results in aggregation and gelation of protein molecules to avoid the exposure of hydrophobic groups to the solvent. BSA has prolate ellipsoidal shape at ambient temperature and we observe no effect of temperature on its structure up to the temperature of about 60º C. At temperatures beyond 60º C, SANS data show the fractal structure with fractal dimension increasing with temperature an indication of gelation followed by aggregation that evolves with increasing temperature. Pressure is believed to unfold the protein through the penetration of water in the hydrophobic patches. It had been known for some of the proteins (e.g. Staphylococcal Nuclease) that pressure of 200 MPa can unfold the protein. However, in the case of BSA protein we have not observed any protein unfolding up to the pressure of 450 MPa. Similar to applying pressure, the presence of urea is known to increase solvation of hydrophobic portions, which leads to unfolding. We have found BSA protein unfolds for urea concentrations greater than 4M and the protein acquire random coil Gaussian chain conformation on unfolding, whose radius of gyration increases with increase in urea concentration. Addition of surfactant denaturates protein by the formation of micelle-like aggregates of surfactant along the unfolded polypeptide chains of the protein. We observe the fractal dimension representing protein-surfactant complex decreases and the overall size of the complex increases on increasing the surfactant concentration. The size of the micelle-like clusters does not show any change while the number of such micelle-like clusters in protein-surfactant complex increases with the surfactant concentration. Amongst all the above denaturating methods used, we have observed protein unfolding is reversible only in case of urea.


Keywords: folding, self-assembly, small angle neutron scattering
Corresponding author: vkaswal@barc.gov.in
PLT06
Synthesis and X-ray Structural Study on the Complexes of Silver(I) Halide with Tricyclohexylephosphine, Diphenyl-(2,4,6-trimethoxy)phenylphosphine, Phenyl-2,4,6-trimethoxyphenyl phosphine, and Tris(2,4,6-trimethoxy)phenylphosphine
Effendy1 and Allan H. White2

1 Jurusan Kimia, FMIPA Universitas Negeri Malang, Jl. Surabaya 6 Malang 65145, Indonesia

2 Chemistry, School of Biomedical, Biomolecular, and Chemical Sciences, The University of Western

Australia, 35 Stirling Highway, Crawley WA 6009, Australia

A diverse array of structures for the complexes of silver(I) halide with triphenylphosphine (PPh3) has been studied. The complexes may be described as being of the type [AgX(PPh3)n] (X = Cl, Br or I). The value of n varies in the range of 1-3. This also indicates that the stoichiometry of the complexes is in the range of 1-3. The complex with stoichiometry 1:1 is a tetramer. There are two structural types of tetramer reported, termed cubane and step or chair. The cubane structure has been reported for [AgX(PPh3)]4 (X = Cl, Br or I), while the step structure has only been reported for [AgI(PPh3)]4. The complex with stoichiometry 1:2 may be a monomer or a dimer. The monomer has a quasi trigonal planar structural type and has only been reported for [AgBr(PPh3)2]. The dimer has been reported for [(PPh3)2Ag(-X)2Ag(PPh3)2] (X = Cl or Br) with silver atom in the distorted tetrahedral environment. The complex with stoichiometry 1:3 has a distorted tetrahedral structural type and has been reported for [AgX(PPh3)3] (X = Cl, Br or I). Changing PPh3 with more hindered ligand such as tricyclohexylephosphine (Pcy3) or derivative of PPh3 such as diphenyl-2,4,6-trimethoxy(phenyl)phosphine (dpmp), phenyl-bis{2,4,6-trimethoxy(phenyl)} phosphine (pdmp), or tris{2,4,6-trimethoxy(phenyl)}phosphine (tmpp) may give complexes with various structural types but with lower range of stoichiometry. Synthesis and X-ray structural study of these complexes has been done with the results summarized below.

Silver(I) halide and PCy3 give complexes with stoichiometry 1:1 and 1:2. The complex with stoichiometry 1:1 is a dimer or cubane. The dimer is observed for [(Pcy3)Ag(-X)2Ag(Pcy3)] (X = Cl or Br). The unusual dimer is observed for [(Pcy3)Ag(-I)2(-py)Ag(Pcy3)] where the pyridine ligand is bonded to two silver atoms. The cubane is observed for [AgI(Pcy3)]4. The complex with stoichiometry 1:2 has a quasi trigonal planar structural type and has been observed for [AgX(Pcy3)2] (X = Cl, Br, I).

Silver(I) halide and dpmp give complexes with stoichiometry 1:1 and 1:2. The complex with stoichiometry 1:1 is a dimer and has been observed for [(dpmp)Ag(-X)2Ag(dpmp)] (X = Cl, Br or I). The complex with stoichiometry 1:2 has a quasi trigonal planar structural type and has been observed for [AgX(dpmp)2] (X = Cl, Br, I).

Silver(I) halide and pdmp also give complexes with stoichiometry 1:1 and 1:2. The complex with stoichiometry 1:1 is a dimer and has been observed for [(pdmp)Ag(-X)2Ag(pdmp)] (X = Cl, Br or I). The complex with stoichiometry 1:2 has a quasi trigonal planar structural type and has been observed for [AgX(pdmp)2] (X = Cl, Br, I).

Silver(I) halide and tmmp only give complexes with stoichiometry 1:1. This complex is a monomer and has been observed for [AgX(tmpp)] (X = Cl or Br). In this complex the silver atom is in a quasi linear environment.

Based on the bond lengths between silver and phosphorous atoms in the complexes obtained, it can be concluded that bulky ligands tend to give complexes with lower range of stoichiometry. In addition, the bulkier the ligand the longer the bond length between the silver and phosphorous atoms.
Keywords:
Corresponding author: fnd299@yahoo.co.uk

PLT07
Expecting the Unexpected. Phase Transitions in Manganese Perovskites
B. J. Kennedy

School of Chemistry, The University of Sydney, Sydney, NSW 2006 Australia

Manganese perovskites, have the general formula AMnO3, and exhibit a rich and diverse range of structures, the precise structure depending on the oxidation state of the manganese, both Mn3+ (d4) and Mn4+ (d3+) are found in perovskite type oxides, the size of the A-type cation and the presence of any vacancies in the lattice. Following the discovery of colossal magnetoresistance in LaMnO3 considerable effort has been made towards understanding the complex interplay between orbital ordering associated with the Jahn-Tellar active Mn3+ ions and the tilting of the MnO6 polyhedra associated with the relative sizes of the cations.


The present work describes structural studies, using a combination of high resolution synchrotron X-ray and neutron diffraction, of three series of manganese perovskites; namely the Mn4+ containing oxides of the type Ca1-xSrxMnO3; and the mixed valence Mn3+/4+ oxides Sr1-xCexMnO3 0.075 < x < 0.4 and Sr0.9-xCaxCe0.1MnO3 0.0 < x < 0.9. In the first series the progressive replacement of the Ca2+ by the smaller Sr2+ cation induces a first order orthorhombic (Pnma) to tetragonal (I4/mcm) transition associated with tilting of the octahedra. Introducing Mn3+ into the structure, by partially replacing Sr2+ with Ce3+, results in a large Jahn-Tellar induced tetragonal distortion of the MnO6 octahedra and the formation of a second orthorhombic phase in Imma. Progressive replacement of Sr by Ca in Sr0.9-xCaxCe0.1MnO3 results in a reduction in the distortion of the unit cell, but an increase in the distortion of the MnO6 octahedra. We present the clearest evidence to date for the independence of the orbital ordering and octahedral titling in these oxides.
Keywords: Manganese Perovskite, Synchrotron X-ray diffraction, Neutron diffraction, Structural Phase Transition
Corresponding author: b.kennedy@chem.usyd.edu.au
PLT08
SANS and SAXS Study of Block and Graft Copolymers Containing Natural and Synthetic Rubbers
H. Hasegawa1

1 Department of Polymer Chemistry, Kyoto University 615-8510, Japan

Small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) are excellent techniques to study nano-scale concentration fluctuations in the two-component polymer systems such as block and graft copolymers and polymer blends. We introduce some of our works on the investigation of the miscibility, phase transitions, microphase-separated structures, interface thicknesses in the block and graft copolymers, which at least contain natural or synthetic rubber as one of their components, using SANS and SAXS.

The first system investigated was natural rubber grafted with poly(methyl methacrylate) (PMMA). The sample was prepared by gamma-ray irradiation on natural rubber latex and methyl methacrylate monomer mixtures in aqueous suspension. The SANS scattering profiles from the cast films exhibited single broad peaks suggesting microphase-separated structures of the graft copolymers in agreement with the transmission electron microscopy (TEM) observations. The Porod analysis of the scattering curve gave the interface thickness of ca. 3 nm.

The second system investigated was a polyisoprene-block-poly(perdeuterated butadienne) diblock copolymer. The temperature and pressure dependences of the miscibility and order-disorder transitions were studied by SANS. It has been found that the system exhibits a lower critical solution temperature (LCST) type phase behavior and pressure enhances the miscibility of the two components of the copolymer.

The third system investigated was polystyrene-block-polyisoprene diblock copolymers having the compositions in the “complex phase window”. The temperature dependent SAXS profiles obtained with synchrotron radiation suggested order-order transitions of the microphase-separated structures from lamellae to Fddd single network structures and then to Gyroid double network structures with increasing temperature. The Fddd structure was first found for a diblock copolymer.
Keywords: small-angle neutron scattering, small-angle X-ray scattering, block copolymer, rubber
Corresponding author: hasegawa@alloy.polym.kyoto-u.ac.jp

PLT09
SANS and SAXS Study of Block and Graft Copolymers Containing Natural and Synthetic Rubbers
X. B. Zeng1, F. Liu1, F. Xie1, G. Ungar1, C. Tschierske2, J. E. Macdonald3

1 Department of Engineering Materials, Sheffield University, Sheffield S1 3JD, UK

2 Institute of Organic Chemistry, University Halle, Kurt-Mothes-Strasse 2, D-06120 Halle, Germany

3 Department of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, UK

Some recent work carried out in our research group on complex structures found in polymers and supramolecular systems, using Small Angle X-ray and Neutron Scattering (SAXS and SANS) methods, are reviewed. These include,



  1. Combined SAXS and SANS study of superlattice structures in pure and mixed model polymers;

  2. Real-time SANS study of transient phases during polymer crystallization;

  3. Columnar phases with polygonal cross-sections in T-shaped polyphilic compounds;

  4. Complex 3-d phases formed by packing spherical objects (e.g. micelles self-assembled from tree-like molecules), including the recently discovered liquid quasi-crystals which possess 12-fold rotational symmetry.

Examples of powder, fibre or surface oriented, and single-domain diffractions will be given. Reconstruction of electron density maps as well as computer modelling are also applied to help solving various complex structures.

Figure 1. A Grazing-Incidence SAXS pattern of a thin film of T-shaped polyphilic liquid crystal forming compound on silicon surface, showing a less oriented phase on the top surface and another well-oriented phase deeper into the film.


Keywords: SAXS, SANS, GI-SAXS, supramolecules, liquid crystal
Corresponding author: X.Zeng@sheffield.ac.uk


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N eutron Scattering Laboratory – BATAN


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