MLZ is a cooperation between:
> Technische Universität München
> Helmholtz-Zentrum Hereon
> Forschungszentrum Jülich
MLZ is a member of:
> LENS
> ERF-AISBL
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MLZ (eng)
Lichtenbergstr.1
85748 Garching
BIODIFF
Diffractometer for large unit cells
This instrument is focussed on cold neutrons. All parameters given here are valid during the current operation of FRM II. Please get in touch with the instrument team well in advance for all further details (length of experiment etc.).
BIODIFF is designed to handle crystals with large unit cells and is dedicated to the structure determination of biological macromolecules. In biological macromolecules, like proteins and nucleic acids, hydrogen atoms play an important role. Hydrogen atoms take part in the substrate binding process and are essential for proton transfer reactions during the catalysis in many enzymes. Therefore, the knowledge about the protonation states of amino acid residues in the active centre of proteins is often crucial for the understanding of their reaction mechanisms. However, hydrogen atoms, especially rather flexible ones, are barely detectable in X-ray structure determinations of proteins. On the other hand, hydrogen atoms are clearly visible in neutron crystallography experiments even at moderate resolutions (dmin < 2.5 Å).
BIODIFF is the first instrument along the neutron guide NL1. Using a pyrolytic graphite monochromator PG(002) the diffractometer covers a tunable wavelength range of 2.7 Å to about 4 Å. Higher order wavelength contaminations are removed by a neutron velocity selector. Using the PG(004) reflex, a wavelength of 2 Å can be realised. At this wavelength, there is an upper limit on the lattice constants of 80 Å for the samples in order to avoid overlapping Bragg reflexes.
The main detector of the diffractometer consists of a neutron imaging plate system in a cylindrical geometry to cover a large solid angle. A fast LiF/ZnS scintillator CCD ca¬mera is foreseen for additional detection abilities. The main advantage of this instrument is the possibility to adapt the wavelength to the size of the sample crystal’s unit cell while operating with a clean monochromatic beam that keeps the background level low.
The main field of application is the neutron structure analysis of proteins, especially the determination of hydrogen atom positions. Typical questions in this field of interest are:
- Enzymatic mechanism (protonation states of amino acids)
- Ligand binding mediated by hydrogen bonds
- Investigation of the hydration shell of proteins
- H/D-exchange pattern as a monitor of structural stability/ accessibility/ flexibility
Besides standard sample environment BIODIFF provides:
- Oxford Cryosystems Cryostream 700 plus with a temperature range of 90 K to 500 K
- Closed cycle cryostat 3.5 – 325 K
- Neutron guide NL-1; supermirror m = 2
- Monochromator:
- Pyrolytic graphite (PG), mosaicity: 0.4 – 0.5°
- Higher order filter:
- Astrium type velocity selector
- transmission 87 % for 2.7 Å
- Wavelength range:
- 2.0 Å with PG(004): 3.0 · 106 n cm-2 s-1. Limit: lattice constants up to 80 Å.
- 2.7 Å with PG(002): 4.0 · 106 n cm-2 s-1. Limit: lattice constants up to 110 Å.
- 3.4 Å with PG(002): 1.8 · 106 n cm-2 s-1
- 4.0 Å with PG(002): 1.0 · 106 n cm-2 s-1
- Collimation by adjustable slits between 1 – 4 mm
- Wavelength resolution at sample position: ∆λ/λ = 2.9 % at 2.7 Å with PG(002)
- Wavelength resolution at sample position: ∆λ/λ = 1.5 % at 2.0 Å with PG(004)
- Beam divergence (no slits):
- 0.8° FWHM horizontal
- 0.7° FWHM vertical
- BaFBr:Eu2+ mixed with Gd2O3
- Dimensions:
- radius: 200 mm
- angular range:
- ±152° horizontal
- ±48° vertical
- Pixel size (quadratic): 125, 250, 500 µm
- Readout time (with erasing): 5 min (for 500 µm pixel size)
- ZnS mixed with 6LiF
- Dimensions:
- Active scintillator area (flat): 200 × 200 mm²
- Distance to sample: 100 mm
- 2Θ-angle around sample position 0° – 113°
- CCD chip with 2048 × 2048 pixels
- Pixel size: 13.5 × 13.5 µm2
- Overall spatial resolution: ≈ 300 × 300 µm2 (limited by scintillator thickness)
- Minimum readout time: ≈ 1 sec (full resolution); < 1 sec (binning mode)
Instrument Scientists
Dr. Andreas Ostermann
Phone: +49 (0)89 289-14702
E-Mail: andreas.ostermann@frm2.tum.de
Dr. Tobias Schrader
Phone: +49 (0)89 158860-743
E-Mail: t.schrader@fz-juelich.de
BIODIFF
Phone: +49 (0)89 289-14565
Operated by
News
Publications
Find the latest publications regarding BIODIFF in our publication database iMPULSE:
Citation of the instrument
Heinz Maier-Leibnitz Zentrum. (2015). BIODIFF: Diffractometer for large unit cells. Journal of large-scale research facilities, 1, A2. http://dx.doi.org/10.17815/jlsrf-1-19
For citation please always include the DOI.
Gallery
MLZ is a cooperation between:
> Technische Universität München> Helmholtz-Zentrum Hereon
> Forschungszentrum Jülich
MLZ is a member of:
> LENS> ERF-AISBL
MLZ on social media: