Small angle neutron scattering at the National Institute of Standards and Technology

Hammouda, Boualem; Krueger, Susan; Cj, Glinka

doi:10.6028/jres.098.003

Cited by 117 publications

(128 citation statements)

References 78 publications

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“…SANS Measurements-The SANS measurements were performed on the NG3 30 m SANS instrument at the National Institute of Standards and Technology Center for Neutron Research in Gaithersburg, MD (15). Unligated CRP solutions were measured at 0.036 and 0.096 mM and unligated CRP* at 0.049 and 0.138 mM in the D 2 O solvent.…”

Section: Methodsmentioning

confidence: 99%

Determination of the Conformations of cAMP Receptor Protein and Its T127L,S128A Mutant with and without cAMP from Small Angle Neutron Scattering Measurements

Krueger¹,

Gorshkova

Brown

et al. 1998

Journal of Biological Chemistry

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The binding of 3Ј,5Ј cyclic adenosine monophosphate (cAMP) to cAMP receptor protein (CRP) 1 activates the transcription of over 20 genes that code for the catabolite enzymes involved in carbohydrate metabolism in Escherichia coli. Results from NMR (1, 2), Raman spectroscopy (3), proteolysis studies (4), small angle x-ray scattering measurements (5), and isothermal titration calorimetry (6) indicate that upon binding to cAMP, CRP undergoes a conformational change to a conformation that promotes specific binding to the catabolite operons to activate transcription in the presence of RNA polymerase. The nature of this conformational change is not known, because only the structures of the cAMP-ligated CRP complex and of the DNAcAMP-ligated CRP complex have been determined from x-ray crystallography studies (7,8).CRP exists as a homodimer of 45,000 g mol Ϫ1 consisting of a ␤-pleated sheet amino-terminal domain, which contains the cAMP binding site and a carboxyl-terminal domain consisting of several ␣-helices that bind to specific DNA sequences. In the crystal phase, the cAMP-ligated CRP dimer is asymmetric where one monomer is in an "open" form in which the ␣-helices are swung out away from the amino-terminal domain and the other monomer is in a "closed" form in which the ␣-helices are swung in close to the amino-terminal domain (7). The amino acid sequence connecting the two domains is, thus, called the "hinge" region. The x-ray crystal structure of the cAMP-ligated CRP dimer complexed with a 30-base pair DNA sequence is exclusively in the closed form (8). Recent energy minimization computations of the two forms in solution show that the lowest energy conformation of the cAMP-ligated CRP dimer is exclusively the closed form in solution (9). The implication is that the asymmetry of the CRP dimer in the crystal lattice is due to crystal packing forces and that the structural change responsible for the activation of transcription is a change from the open to the closed form in solution. This is substantiated by NMR measurements on fluorinated derivatives of CRP, which imply that the conformational change involves the hinge region (1), and proton NMR measurements, which show that CRP in solution tightens up and becomes more rigid upon binding of cAMP (2).There is, however, evidence that the conformational change may not simply involve a transition from the open to the closed form of CRP upon binding to cAMP in solution. A comparison of the secondary structure of free CRP and cAMP-ligated CRP by Raman spectroscopy (3) shows a structural shift from 44% ␣-helix, 28% ␤-strand, 18% turn, and 10% undefined in the free form to 37% ␣-helix, 33% ␤-strand, 17% turn, and 12% undefined in the ligated form, implying that the conformational change does not conserve the ␣-helical and ␤-strand structure as it would in a shift of the CRP dimer from the exclusively open to the closed form in solution. A conformational change involving alterations in the ␣-helical and ␤-strand structure of CRP is also implied by an empirical model of CR...

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Section: Methodsmentioning

confidence: 99%

Determination of the Conformations of cAMP Receptor Protein and Its T127L,S128A Mutant with and without cAMP from Small Angle Neutron Scattering Measurements

Krueger¹,

Gorshkova

Brown

et al. 1998

Journal of Biological Chemistry

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“…The SANS measurements were performed at the NIST-CNRF using the 30m NSF instrument (Hammouda, Krueger & Glinka, 1993). All samples were measured in a vacuum at room temperature with the instrument in two resolution configurations.…”

Section: Methodsmentioning

confidence: 99%

Small-angle neutron scattering study of dislocations in deformed single-crystal copper

Heuser

1994

J Appl Cryst

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Small-angle neutron scattering measurements of deformed single-crystal copper have been performed over a wave-vector transfer range of 0.0655 <__ Q < 1.32 nm -l. The measurements included four samples deformed in compression at room temperature along the [110] direction to 6.8, 15.6, 35.0 and 54.3% reduction in thickness and an undeformed reference sample. The response of the reference sample followed the Porod law at lowest (Q and was, at least in part, the result of scattering from the external surfaces of the sample. The radially averaged net cross sections were found to increase with increasing deformation, while the power-law exponent n (dZ'/d~ ~x 1/Q '~) decreased from 7t _~ 3 to n ~ 2.2 with increasing deformation. The scattering response of the two most deformed samples was noticeably anisotropic. Analysis of this anisotropy revealed strong 1/Q 2 scattering perpendicular to the { 111 } dislocation slip planes, in agreement with the theoretical work of Seeger [J. . Phys. (1959), 30, 629--637]. The decrease in the radially averaged power-law exponent is therefore attributed to strong 1/Q 2 behavior at the highest levels of deformation. Bulk-averaged edge dislocation densities that varied systematically from approximately 1 × 10 ~° to 5 × 101° cm -2 were obtained from the measured data. Appl

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“…The scattering data were corrected on a cell-by-cell basis for empty-beam scattering, spectral intensity, and detector efficiency following previous outlined procedures, and converted to an absolute differential scattering cross-section per unit sample volume (d⌺/d⍀(q), cm Ϫ1 ) using the absolute cross-section of standards determined by a direct neutron flux measurement (NIST PolyB1 (polystyrene) at 13.17m detector position and NIST Silica gel B1 at 5 m detector position). [25][26][27] The absolute calibration of the intensity is within Ϯ5%. 25 Neutron transmission of the samples ranged between 60 -70% for pellets 0.7-1.1 mm thick.…”

Section: Small-angle Neutron Scattering: Data Collectionmentioning

confidence: 99%

“…[25][26][27] The absolute calibration of the intensity is within Ϯ5%. 25 Neutron transmission of the samples ranged between 60 -70% for pellets 0.7-1.1 mm thick.…”

Section: Small-angle Neutron Scattering: Data Collectionmentioning

confidence: 99%

Chain conformation of rod-like polymers in the melt: Small-angle neutron scattering of poly(benzoyl paraphenylene)

Vaia

Krishnamoorti

Benner

et al. 1998

J. Polym. Sci. B Polym. Phys.

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Small angle neutron scattering at the National Institute of Standards and Technology

Cited by 117 publications

References 78 publications

Determination of the Conformations of cAMP Receptor Protein and Its T127L,S128A Mutant with and without cAMP from Small Angle Neutron Scattering Measurements

Determination of the Conformations of cAMP Receptor Protein and Its T127L,S128A Mutant with and without cAMP from Small Angle Neutron Scattering Measurements

Small-angle neutron scattering study of dislocations in deformed single-crystal copper

Chain conformation of rod-like polymers in the melt: Small-angle neutron scattering of poly(benzoyl paraphenylene)

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