Browsing by Author "Majkrzak, CF"

Now showing 1 - 5 of 5
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    Dynamical theory calculations of spin-echo resolved grazing-incidence scattering from a diffraction grating
    (Wiley-Blackwell, 2010-06-01) Ashkar, R; Stonaha, P; Washington, AL; Shah, VR; Fitzsimmons, MR; Maranville, B; Majkrzak, CF; Lee, WT; Schaich, WL; Pynn, R
    Neutrons scattered or reflected from a diffraction grating are subject to a periodic potential analogous to the potential experienced by electrons within a crystal. Hence, the wavefunction of the neutrons can be expanded in terms of Bloch waves and a dynamical theory can be applied to interpret the scattering phenomenon. In this paper, a dynamical theory is used to calculate the results of neutron spin-echo resolved grazing-incidence scattering (SERGIS) from a silicon diffraction grating with a rectangular profile. The calculations are compared with SERGIS measurements made on the same grating at two neutron sources: a pulsed source and a continuous wave source. In both cases, the spin-echo polarization, studied as a function of the spin-echo length, peaks at integer multiples of the grating period but there are some differences between the two sets of data. The dynamical theory explains the differences and gives a good account of both sets of results. © 2010, Wiley-Blackwell.
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    New sources and instrumentation for neutrons in biology
    (Elsevier, 2008-04-18) Teixeira, SCM; Zaccai, G; Ankner, J; Bellissent-Funel, MC; Bewley, RI; Blakeley, MP; Callow, P; Coates, L; Dahint, R; Dalgliesh, R; Dencher, NA; Forsyth, VT; Fragneto, G; Frick, B; Gilles, R; Gutberlet, T; Haertlein, M; Hauß, T; Häußler, W; Heller, WT; Herwig, K; Holderer, O; Juranyi, F; Kampmann, R; Knott, RB; Krueger, S; Langan, P; Lechner, RE; Lynn, GW; Majkrzak, CF; May, RP; Meilleur, F; Mo, Y; Mortensen, K; Myles, DAA; Natali, F; Neylon, C; Niimura, N; Ollivier, J; Ostermann, A; Peters, J; Pieper, J; Rühm, A; Schwahn, D; Shibata, K; Soper, AK; Strässle, T; Suzuki, J; Tanaka, I; Tehei, M; Timmins, P; Torikai, N; Unruh, T; Urban, V; Vavrin, R; Weiss, K
    Neutron radiation offers significant advantages for the study of biological molecular structure and dynamics. A broad and significant effort towards instrumental and methodological development to facilitate biology experiments at neutron sources worldwide is reviewed. © 2008, Elsevier Ltd.
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    Round robin sample for neutron reflectometry
    (International Conference on Neutron Scattering, 2017-07-12) Nelson, A; Dura, JA; Majkrzak, CF; Newby, R
    Were a scientist to visit one of the many neutron and X-ray reflectometers in use around the world they would expect that if the same sample were measured on any of those instruments the results derived from the experiment would be comparable and reproducible. Each user measurement relies on many assumptions, including: good calibration of the instrument, valid measurement processes, valid data reduction algorithms, good knowledge of resolution functions, etc. It would be unfortunate if data measured across a class of instruments were not comparable and reproducible as a large body of research into interfaces is underpinned by these techniques. The small-angle neutron scattering community investigated this recently [1], with a series of measurements of a common sample at different facilities, spanning a range of instruments with different design characteristics. This round robin was able to verify the reproducibility and reliability of the instruments taking part, as well as highlighting areas for improvement. We have therefore decided to initiate a similar process for neutron and X-ray reflectometers. To date the project has identified, synthesised, and characterised two suitable samples that lie at opposite ends of the typical size range studied by reflectometry. Here we give a brief overview of these preliminary characterisations, and propose an experimental design and methodology for instruments taking part.
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    The structural orientation of antibody layers bound to engineered biosensor surfaces
    (Elsevier, 2011-04-01) Le Brun, AP; Holt, SA; Shah, DSH; Majkrzak, CF; Lakey, JH
    This paper describes a membrane protein array that binds immunoglobulin G at its constant regions whilst leaving the variable regions free to bind antigen. The scaffold of the array is the transmembrane domain of outer membrane protein A (tOmpA) from Escherichia colt engineered to assemble as an oriented monolayer on gold surfaces via a single cysteine residue. Other protein domains can be fused to the N and C termini of the scaffold. In this study we use circularly permuted ctOmpA fused to two Z domains of Staphylococcus aureus protein A (ZZctOmpA) to create the immunoglobulin G-binding array. The solution structure of the engineered proteins was assessed by circular dichroism spectroscopy. Assembly of the array, attachment of antibodies and antigen binding were measured using surface plasmon resonance and neutron reflection. Compared to mouse IgG2, polyclonal IgG from rabbit bound very strongly to ZZctOmpA and the dissociation of the immunoglobulin was slow enough to allow neutron reflection studies of the assembled layer with antigen. Using both magnetic and isotopic contrasts a complete layer by layer model was defined which revealed that the 223 A high layer contains antibodies in an upright orientation. (C) 2011 Elsevier Ltd. All rights reserved.
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    Structurally characterising biomolecular recognition at the solid-liquid interface: an example using immunoglobulin G bound to membrane protein arrays on gold
    (Neutron Scattering Society of America, 2010-06-29) Le Brun, AP; Holt, SA; Lakey, JH; Shah, D; Majkrzak, CF
    Proteins can be immobilised on surfaces to make arrays with potential uses in tissue engineering, proteomics and point of use diagnostic devices. Outer membrane proteins (OMP) from Escherichia coli have a beta-barrel structure, making ideal protein engineering scaffolds for building arrays. The proteins can be immobilised onto flat gold surfaces by introducing a cysteine residue into their periplasmic turns. The thiol group of the cysteine will form a strong gold-thiolate bond immobilising the OMP to the surface in a specific and correct orientation. The membrane layer is completed by the immobilisatin of a lipid with a thiol head group to the gold surface. Here we use the transmembrane section of the monomeric protein OmpA (TmOmpA). The Z domain of Staphylococcus aureau protein A has been engineered into the N - terminal of a circularly permuted TmOmpA to create the protein ZZctOmpA. The Z domain can bind immunoglobulin G (IgG) at its constant region leaving the variable regions free to bind antigen. The structure of this model protein array was probed using magnetic contrast neutron reflection (MCNR). MCNR uses polarised neutrons which reflect differently from a magnetic metal layer according to their two spin states (spin up and spin down). The magnetic layer deposited under the gold surface and provides additional scattering length density contrast to very complex layer systems without needing to make any changes to the biological layer. The collection of two complimentary but independent data sets allows for more accurate modelling of the resulting high resolution data. The data presented will show the assembly steps for creating the array detailing the surfaces used, the ZZctOmpA and lipid components as well as information on the orientation of bound antibody and antigen.