Biological X-ray diffraction measurements with a novel two-dimensional gaseous pixel detector

Sarvestani, A.; Amenitsch, Heinz; Bernstorff, Sigrid; Besch, H.J.; Menk, R.H.; Orthen, A.; Pavel, N.; Rappolt, Michael; Sauer, N.; Walenta, A.H.

doi:10.1107/s0909049599007657

Cited by 8 publications

(3 citation statements)

References 16 publications

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“…As one example, in figure 4 the small angle pattern of a phospholipid is shown. These measurements, which are described in detail in Sarvestani et al (1998b), have proven that the intensity precision is at the Poisson limit, the position resolution is good (about 300 µm in FWHM) and the image formation is correct. For all the measurements described here a Xe/Ar-CH 4 gas mixture (45%, 45%, 10%) at normal pressure was used.…”

Section: Measurements and Resultsmentioning

confidence: 87%

Novel detector systems for time resolved SAXS experiments

Menk¹,

Sarvestani²,

Amenitsch³

et al. 2000

J Appl Cryst

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Two novel detector concepts will be presented which together satisfy, in principle, most of the requirements of modern diffraction experiments with synchrotron radiation. One is based on a gaseous single photon counter with asynchronous read out and interpolating position encoding, combining the advantages of a pure pixel read out (high local and global rate capability) and of a projecting read out (small number of channels). In order to demonstrate the suitability of this detector for X-ray diffraction applications, measurements at the synchrotron radiation source Elettra (Trieste, Italy) have been performed with the prototype (140 x 140 pixels) recording diffraction patterns from different biological samples (a phospholipid and a protein crystal). These measurements have proven the good spatial resolution, the high intensity precision and the high local rate capability. Moreover, the single photon read out was utilized in order to perform highly time-resolved measurements in case of SAXS studies and to apply fine phi-slicing in case of protein crystallography. The other detector system is a highly segmented one-dimensional prototype ionization chamber with an active area of 5 * 30 mm 2 . Fast recording sequences in the order of 200µs are ensured by a shielding grid, which is based on the principle of the recently invented MicroCAT structure. The grid enables new modes of operation such as gas amplification in combination with integration. In this fashion imaging on a sub photon noise level with respect to the integration time is possible. A continuous transition from integrating mode to single photon counting mode results in a huge dynamic range that covers at least 8 orders of magnitude. Preliminary experiments on biological samples will be presented.

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Section: Measurements and Resultsmentioning

confidence: 87%

Novel detector systems for time resolved SAXS experiments

Menk¹,

Sarvestani²,

Amenitsch³

et al. 2000

J Appl Cryst

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“…Detailed information about the detector can be found elsewhere (Besch et al, 1997;Sarvestani et al, 1998a;Wagner et al, 2003;Orthen et al, 2003a). A review of a previous, similar detector with smaller sensitive detection area and a less sophisticated position reconstruction, with a different gas gain structure and with slower electronics and readout has also been published earlier (Sarvestani et al, 1999a).…”

Section: Detector Setupmentioning

confidence: 99%

Development of a two-dimensional virtual-pixel X-ray imaging detector for time-resolved structure research

Orthen¹,

Wagner²,

Martoiu³

et al. 2004

J Synchrotron Radiat

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An interpolating two-dimensional X-ray imaging detector based on a single photon counter with gas amplification by GEM (gas electron multiplier) structures is presented. The detector system can be used for time-resolved structure research down to the µs-time domain. The prototype detector has been tested at the SAXS beamline at ELET-TRA synchrotron light source with a beam energy of 8 keV to test its capabilities in the rough beamline environment. The imaging performance is examined with apertures and standard diffraction targets. Finally, the application in a time-resolved lipid temperature jump experiment is presented.

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“…A two-dimensional gaseous pixel detector prototype has been made and tested; 36 it has the advantage of very low dead time and fast readout per pixel (as low as 10 À7 s), and is based on well established science, the ionization of a detector gas (Xe/CO 2 in this case) in a strong electric ¢eld, as employed for many years in multi wire proportional counter (MWPC) detectors. The device has a small active area (28 Â 28 mm 2 , but the authors suggest that this should easily be scalable to 1 Â 1 m 2 ) and only 7 Â 7 pixels, but by using a scheme of 20 Â 20 pixel interpolation, this can be treated effectively as 140 Â 140 pixels, each 200 Â 200 mm 2 .…”

Section: Instrumentationmentioning

confidence: 99%

5 Molecular structure from X-ray diffraction

Powell

2000

Annu. Rep. Prog. Chem., Sect. C

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The last of these reports appeared four years ago; 1 a number of major advances in structure elucidation have appeared in laboratories in that period, mostly in the ¢eld of macromolecular structure determination. This is largely because sub-100 non-hydrogen atom structure solution has become almost routine, with extremely robust solution and re¢nement programs being complemented by rapid data collection from single crystal samples. In many cases, the role of the in-house crystallographer in chemistry departments is to provide a service to synthetic chemists in an analogous way to that of NMR spectroscopists ¢fteen or twenty years ago. Many chemical crystallographers have used this as an opportunity to study more dif¢cult structures, for example larger molecules from both single crystal and powder methods, using twin datasets, and looking more closely at structures in charge density studies.This increased ease has not removed the perils of being ``Marshed''; the well-known investigator into errors in space group determination has examined structures deposited into the Cambridge Structural Database (CSD) with space group P1, of which more than 20% are incorrect. 2 The majority of errors appear to be due to typographical errors in the original publication, but a signi¢cant minority are due to incorrect space group assignment (usually authors missing a centre of inversion, and assigning P1 rather than P1, or not recognizing higher symmetry, e.g., assigning P1 (triclinic) rather than C2 (monoclinic). However, the author notes that in some cases of true P1 structures, the deviation from centrosymmetry is as small as 0.1 Ð, and would be expected to lead to dif¢culties in re¢nement unless the problem had been recognized, as the following example illustrates.The solution and re¢nement of the antibiotics Emycin E and D provides a warning not to abide by conventional wisdom under all circumstances. 3 Both antibiotics crystallize in a triclinic space group with two molecules in the asymmetric unit (Z 2). The dataset for Emycin E was in accordance with the normal measure of centricity, a mean hjE 2 À 1ji value of 0.978 (the expected value for a centrosymmetric dataset is 0.968, and is 0.736 for acentric), while that for Emycin D was 0.829. Both can be re¢ned to low residual indices (R-factors) in space group

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Biological X-ray diffraction measurements with a novel two-dimensional gaseous pixel detector

Cited by 8 publications

References 16 publications

Novel detector systems for time resolved SAXS experiments

Novel detector systems for time resolved SAXS experiments

Development of a two-dimensional virtual-pixel X-ray imaging detector for time-resolved structure research

5 Molecular structure from X-ray diffraction

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