A multiwire proportional chamber as an area detector for protein crystallography

Cork, C.; Fehr, D.; Hamlin, R.; Vernon, W.; Xuong, N.-H.; Perez‐Mendez, V.

doi:10.1107/s0021889874009757

Cited by 81 publications

(30 citation statements)

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“…More sophisticated, and much higher speed, dataacquisition systems have been described by Cork et al (1973Cork et al ( , 1974 and Klesse & Kostorz (1976) in which the mapping is performed by external hardware, and the data are stored in memory external to the CPU. We have developed an interface in which each of the two major functions is also performed by separate highspeed hardware.…”

Section: The Interfacementioning

confidence: 99%

The ORNL 10-meter small angle X-ray scattering camera

Hendricks¹

1978

J Appl Crystallogr

175

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A new small-angle X-ray scattering camera which utilizes a rotating-anode X-ray source, crystal monochromatization of the incident beam, pinhole collimation, and a two-dimensional position-sensitive proportional counter has been developed. Because the sizes of the X-ray focal spot, the sample and the resolution element of the detector are each approximately 1 x 1 mm, the camera was designed so that the focal spot-to-sample and sample-to-detector distances may each be varied in 0-5 m increments up to 5 m to provide a system resolution in the range 0.5 to 4.0 mrad. A large, general-purpose specimen chamber has been provided into which a wide variety of special-purpose specimen holders can be mounted. The detector has an active area of 200 x 200 mm and has up to 200 x 200 resolution elements. The data are recorded in the memory of a minicomputer by a high-speed interface which uses a microprocessor to map the position of an incident photon into an absolute minicomputer memory address. With this interface, over 105 events s-1 can be recorded. The data recorded in the computer memory can be processed on-line by a variety of programs designed to enhance the user's interaction with the experiment. Among these are routines for background and detector-sensitivity correction, contour and perspective plotting of the two-dimensional data, a variety of averaging schemes for determining circular averages and/or one-dimensional slices of the data, file-management programs to handle the large quantity of data produced by a two-dimensional detector, and an interactive package for communications with a central computing facility via a dedicated hardwired link. At the highest angular resolution (0.4 mrad) the flux incident on the specimen is 1.0 x 106 photons s-1 with the X-ray source operating at 45 kV and 100 mA. The performance of the instrument is demonstrated with several examples, among which are scattering patterns from voids in neutron-irradiated nickel, plastically deformed polyethylene and collagen fibrils. Results from a kinetic study of the crystallization of polyethylene are also reported.

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Section: The Interfacementioning

confidence: 99%

The ORNL 10-meter small angle X-ray scattering camera

Hendricks¹

1978

J Appl Crystallogr

175

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“…The precision of the chamber data is also better with an intensity reliability R of 5 % as compared with 6"7 % from the diffractometer data. The difference Patterson maps between parent and heavy-atom derivative data show very clearly the positions of the heavy atoms.We have reported previously the use of an argon-filled multiwire proportional chamber as an area X-ray detector for protein crystallography (Cork, Fehr, Hamlin, Vernon, Xuong & Perez-Mendez, 1973. Since then we have successfully built a xenon-filled chamber with much higher photon-detection efficiency, better spatial resolution and more uniform quantum-detection efficiency.…”

mentioning

confidence: 99%

“…We have reported previously the use of an argon-filled multiwire proportional chamber as an area X-ray detector for protein crystallography (Cork, Fehr, Hamlin, Vernon, Xuong & Perez-Mendez, 1973. Since then we have successfully built a xenon-filled chamber with much higher photon-detection efficiency, better spatial resolution and more uniform quantum-detection efficiency.…”

mentioning

confidence: 99%

“…When the differential pressure rises above 0-5 cm of water, the excess gas mixture bubbles out of the chamber through a simple oil plug manometer. It takes about seven liters to fill the chamber and an additional ten to fifteen liters to keep it running for about three months.The electronic readout and storage system has been described elsewhere (Cork et al, 1973. When a photon is detected, its position on the chamber is decoded giving a binary coded X and Y address (8 bits x 8 bits); the contents of a corresponding location in the mass core are then incremented by one.…”

mentioning

confidence: 99%

“…The electronic readout and storage system has been described elsewhere (Cork et al, 1973. When a photon is detected, its position on the chamber is decoded giving a binary coded X and Y address (8 bits x 8 bits); the contents of a corresponding location in the mass core are then incremented by one.…”

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confidence: 99%

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A xenon-filled multiwire arc detector for X-ray diffraction

Cork¹,

Hamlin²,

Vernon³

et al. 1975

Acta Cryst Sect A

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A xenon-filled multiwire proportional chamber with high and uniform photon-detection efficiency has been built and incorporated into a high-speed data-collection system for protein crystallography. This system has been used to collect more than 200 000 reflection intensities from one parent and four heavy-atom derivative crystals of a complex of dihydrofolate reductase and metho-trexate (a cancer drug). Its data collection rate is about 30 times faster than the rate of a standard diffractometer (1400 reflection intensities per hour versus 50 reflection intensities per hour). The precision of the chamber data is also better with an intensity reliability R of 5 % as compared with 6"7 % from the diffractometer data. The difference Patterson maps between parent and heavy-atom derivative data show very clearly the positions of the heavy atoms.We have reported previously the use of an argon-filled multiwire proportional chamber as an area X-ray detector for protein crystallography (Cork, Fehr, Hamlin, Vernon, Xuong & Perez-Mendez, 1973. Since then we have successfully built a xenon-filled chamber with much higher photon-detection efficiency, better spatial resolution and more uniform quantum-detection efficiency. This chamber is now incorporated into a high-speed data-collection system for protein crystallography. The system collects reflection intensities at a rate about 30 times faster than a standard diffractometer. The precision of the new data is better than that obtained with the diffractometer.The advantage of a xenon chamber over an argon-filled chamber is higher photon-detection efficiency. Xenon is, however, much more expensive than argon so the chamber enclosure must be carefully built to reduce gas leakage. The new chamber has three electrodes: one beryllium window and two wire detection planes. The window, made of a flat beryllium plate (1 mm thick), is mounted in electrical contact with the aluminum enclosure. The two detection planes are similar to those in the previously described argon chamber. The center electrode consists of 150 horizontal wires (20 pm stainless steel with 2 mm spacing). The back electrode consists of 300 vertical wires (50 pm of stainless steel with 1 mm spacing). The two wire planes are mounted on 4 mm thick fiber-glass frames and stacked behind the beryllium window. The aluminum enclosure is composed of three parts: a picture frame holding the front window, another picture frame containing the detection planes and a back plate. The three parts are mounted together with O-rings to eliminate gas leakage. There is enough extra room inside the container for the two delay lines used in the read-out process . All electrical feedthrough connections are standard B.N.C. seated in a leaktight adhesive sealant. The chamber is filled with a gas mixture of 90 % xenon and 10 % CO2 at a pressure of about 1 atm. The center electrode is maintained at 2.8 kV, the front window and the aluminum container are grounded. The back electrode is held at -80 V. The front window has to be kept flat to withi...

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X‐Ray Cryoenzymology

Fink

Petsko

1981

Advances in Enzymology - And Related Areas of Molecular Biology

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A multiwire proportional chamber as an area detector for protein crystallography

Cited by 81 publications

References 6 publications

The ORNL 10-meter small angle X-ray scattering camera

The ORNL 10-meter small angle X-ray scattering camera

A xenon-filled multiwire arc detector for X-ray diffraction

X‐Ray Cryoenzymology

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