A CCD-based area detector for X-ray crystallography using synchrotron and laboratory sources

Phillips, W. A.; Li, Youli; Stanton, Martin; Xie, Juanhui; O'Mara, Daniel M.; Kalata, K.

doi:10.1016/0168-9002(93)90830-b

Cited by 14 publications

(6 citation statements)

References 18 publications

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“…The crystal lattice, which contains 65% solvent volume, is stable from pH 7-10 in 0.1 M monovalent cation salt solutions (3) and from pH 5-11 in 1 M Na2SO4. The pH-dependent local conformational changes and coupled binding of monovalent cations, which have been crystallographically characterized in pH range [7][8][9][10][11] (4), demonstrate the usefulness of this system for studying the effects of altered electrostatic interactions on the protein and solvent structure. Following our observation (4) that cubic insulin crystals in alkaline 0.1-1 M salt solutions bind 1,2-dichloroethane (ClH2C-CH2CI) with unit occupancy at a site on the dimer axis ( Fig.…”

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Stereospecific dihaloalkane binding in a pH-sensitive cavity in cubic insulin crystals.

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Fontano

Bhyravbhatla

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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Crystallographic analysis at 2-A resolution of the selective binding of dihalogenated methane, ethane, and ethylene compounds in the cavity on the cubic insulin dimer axis provides a model for anesthetic-protein interactions. At pH 6-11, 1,2-dichloroethane binds isomorphically in the righthanded cis-conformation, displacing four water molecules from the invariant cavity. Lowering the pH to 5.7 in 1 M Na2SO4 without dihaloalkanes induces a cooperative structural transition in which the dyad cavities between B13 glutamate pairs are constricted, and SO2-ions are bound by rearranged triads of Bi NH' groups. In the presence of dichloroethane at pH 5-5.5, the equilibrium is shifted to a mixture of the ligand-bound and ligand-excluding cavity structures, with halfoccupancy of the sulfate sites, exemplifying how a volatile anesthetic can act as an allosteric effector. Measurements at pH 9 of the occupancies of structurally similar dihaloalkanes demonstrate a high degree of binding selectivity. Induced polarization of the ligand and bound water by the charge distribution in the binding cavity apparently provides the selective electrostatic interactions that discriminate between dihaloalkanes of comparable size and polarity.Insulin (51 amino acids, 5.8 kDa) crystallizes from zinc-free alkaline solutions as a symmetric dimer arranged in orthogonal cross-connected rows in the cubic space group I213 (a = 78.9 A) (1, 2). The crystal lattice, which contains 65% solvent volume, is stable from pH 7-10 in 0.1 M monovalent cation salt solutions (3) and from pH 5-11 in 1 M Na2SO4. The pH-dependent local conformational changes and coupled binding of monovalent cations, which have been crystallographically characterized in pH range 7-11 (4), demonstrate the usefulness of this system for studying the effects of altered electrostatic interactions on the protein and solvent structure. Following our observation (4) that cubic insulin crystals in alkaline 0.1-1 M salt solutions bind 1,2-dichloroethane (ClH2C-CH2CI) with unit occupancy at a site on the dimer axis ( Fig. 1), we have characterized this binding at pH 5-11 and compared the binding of similar dihaloalkanes at pH 9. § Such binding exemplifies the type of hydrophobic ligand-protein interactions that may underlie the action of inhalational general anesthetics (6, 7). MATERIALS AND METHODSCrystal Preparation and X-Ray Data Collection. Cubic Zn-free crystals of bovine insulin, grown from phosphate buffer at pH 9 (1, 4), were equilibrated by dialysis against sodium salt solutions that varied in pH from 5 to 11 and subsequently equilibrated with liquid dihaloalkanes. Dihaloalkane binding was discovered by exposing the crystals to 1,2-dichloroethane as solvent for Formvar, which was applied in the capillary to cast an encasing film that prevents crystal slippage (8). Binding at the dyad site, as detected by x-ray diffraction, was complete after 30-sec direct exposure to liquid dichloroethane or after overnight soaking in a saturated aqueous solution. The x-ray data were collect...

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mentioning

confidence: 99%

Stereospecific dihaloalkane binding in a pH-sensitive cavity in cubic insulin crystals.

Gursky

Fontano

Bhyravbhatla

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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“…Protein crystallography data have been collected successfully for more than 20 years using charge-coupled device (CCD) detectors. Many groups have been involved in developing CCD detectors (Strauss et al, 1990;Stanton et al, 1993;Phillips et al, 1993;Thiel et al, 1995;Tate et al, 1995;Pokrić et al, 2002), including a very successful program located at Argonne National Laboratory, which created several CCD detectors with fiber-optic tapers that were used for many years at the Structural Biology Center, sector 19, at the Advanced Photon Source (APS) (Westbrook & Naday, 1997;Naday et al, 1998Naday et al, , 1999. These detectors were eventually replaced by commercial detectors from Area Detector Systems Corporation (ADSC) (12550 Stowe Drive, Poway, California 92064, USA).…”

Section: Introductionmentioning

confidence: 99%

Taking a look at the calibration of a CCD detector with a fiber-optic taper

et al. 2016

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At the Structural Biology Center beamline 19BM, located at the Advanced Photon Source, the operational characteristics of the equipment are routinely checked to ensure they are in proper working order. After performing a partial flat-field calibration for the ADSC Quantum 210r CCD detector, it was confirmed that the detector operates within specifications. However, as a secondary check it was decided to scan a single reflection across one-half of a detector module to validate the accuracy of the calibration. The intensities from this single reflection varied by more than 30% from the module center to the corner of the module. Redistribution of light within bent fibers of the fiber-optic taper was identified to be a source of this variation. The degree to which the diffraction intensities are corrected to account for characteristics of the fiber-optic tapers depends primarily upon the experimental strategy of data collection, approximations made by the data processing software during scaling, and crystal symmetry.

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“…A number of CCD-based x-ray detectors have been developed at Brandeis University for macromolecular crystallography. [1][2][3][4][5][6] The detector we describe here is based on these designs, with components and parameters optimized for screening mammography. The design is based on an array of cooled CCDs, each fiber optically coupled to a common phosphor.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the detective quantum efficiency of a developmental detector for digital mammography

et al. 1999

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We are developing a modular detector for applications in full field digital mammography and for diagnostic breast imaging. The detector is based on a design that has been refined over the past decade for applications in x-ray crystallography [Kalata et al., Proc. SPIE 1345, 270-279 (1990); Phillips et al. ibid. 2009, 133-138 (1993), Phillips et al., Nucl. Instrum. Methods Phys. Rev. A 334, 621-630 (1993)]. The full field mammographic detector, currently undergoing clinical evaluation, is formed from a 19 cm x 28 cm phosphor screen, read out by a 2 x 3 array of butted charge-coupled device (CCD) modules. Each 2k x 2k CCD is optically coupled to the phosphor via a fiber optic taper with dimensions of 9.4 cm x 9.4cm at the phosphor. This paper describes the imaging performance of a two-module prototype, built using a similar design. In this paper we use cascaded linear systems analysis to develop a model for calculating the spatial frequency dependent noise power spectrum (NPS) and detective quantum efficiency (DQE) of the detector using the measured modulation transfer function (MTF). We compare results of the calculation with the measured NPS and DQE of the prototype. Calculated and measured DQEs are compared over a range of clinically relevant x-ray exposures and kVps. We find that for x-ray photon energies between 10 and 28 keV, the detector gain ranges between 2.5 and 3.7 CCD electrons per incident x-ray, or approximately 5-8 electrons per absorbed x ray. Using a Mo/Mo beam and acrylic phantom, over a detector entrance exposure range of approximately 10 to 80 mR, the volume under the measured 2-d NPS of the prototype detector is proportional to the x-ray exposure, indicating quantum limited performance. Substantial agreement between the calculated and measured values was obtained for the frequency and exposure dependent NPS and DQE over a range of tube voltage from 25 to 30 kVp.

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A CCD-based area detector for X-ray crystallography using synchrotron and laboratory sources

Cited by 14 publications

References 18 publications

Stereospecific dihaloalkane binding in a pH-sensitive cavity in cubic insulin crystals.

Stereospecific dihaloalkane binding in a pH-sensitive cavity in cubic insulin crystals.

Taking a look at the calibration of a CCD detector with a fiber-optic taper

Analysis of the detective quantum efficiency of a developmental detector for digital mammography

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