K-edge anomalous scattering in rubidium hydrogen tartrate

Templeton, L. K.; Templeton, David H.

doi:10.1107/s002188988901023x

Cited by 10 publications

(13 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Using the computer program of Blessing (1984), integrated intensities were derived from the intensity prof'lle recorded at 96 points for each reflection. An analytical absorption correction (Templeton & Templeton, 1973) gave intensity correction factors in the range 1.029-1.038. A total of 7233 independent reflections were obtained, of which 5564 showed F 2 > 2.5tr(F2).…”

Section: Methodsmentioning

confidence: 99%

Electrostatic properties of β-cytidine and cytosine monohydrate from Bragg diffraction

Chen¹,

Craven²

1995

Acta Crystallogr Sect B

View full text Add to dashboard Cite

1081electrostatic potential in the expected N lone-pair position as XN is increased incrementally from 0 to 48.5 ° . These calculations are consistent with the crystallographic evidence that all N...H contacts within the sum of van der Waals radii (2.75 A) that have XN > 35° and PH > 130° may be classified as hydrogen bonds. These N...H contacts are closely aligned with the assumed N lone-pair vector and such evidence is normally taken to infer an interaction between H(8+) and the lone-pair density. However, by analogy with the perpendicular approach of truly 'non-bonded' H to planar Nsp 2 systems (XIV), the lone-pair direction is also the approach direction of minimal steric hindrance to sp 3 hybridized N atoms (XV). Despite this analogy, we feel that the crystallographic results presented here provide tentative evidence that the incoming donor H atom tracks the changing direction of the N lone-pair vector as XN increases from 35 ° to --,60 ° during the latter phases of the Nsp2--+ Nsp 3 transition.We are indebted to Professor G. Gilli AbstractThe charge-density distribution in the crystal structure of the nucleoside fl-cytidine at 123 K has been determined * Author for correspondence.© 1995 International Union of Crystallography Printed in Great Britain -all rights reserved from X-ray diffraction data (Ag Kot, 2 = 0.5608 J~) using all 7233 reflections with sin0/2 < 1.14,~ -1. Maps of electrostatic potential for the cytosine base in cytidine are similar to those derived from previous charge-density studies of cytosine monohydrate and 1-fl-D-arabinosylcytosine, after taking chemical differences into account.

show abstract

Section: Methodsmentioning

confidence: 99%

Electrostatic properties of β-cytidine and cytosine monohydrate from Bragg diffraction

Chen¹,

Craven²

1995

Acta Crystallogr Sect B

View full text Add to dashboard Cite

show abstract

“…), respectively [see e.g. the tabulated values off ~ and f" in Templeton, Templeton & Phizackerley (1980) and Templeton, Templeton, Phillips & Hodgson (1980)]. For each wavelength the crystallographic data were collected in a total of 15 blocks whereby each block comprised two exposures, each involving a 4 ° rotation.…”

Section: Introductionmentioning

confidence: 99%

MAD Phasing Strategies Explored with a Brominated Oligonucleotide Crystal at 1.65Å Resolution

Peterson¹,

Harrop²,

McSweeney³

et al. 1996

J Synchrotron Radiat

View full text Add to dashboard Cite

The crystal structure of a brominated oligonucleotide d(CGCG(Br)CG), chemical formula C(114)N(48)O(68)P(10)Br(2), has been analysed by multiwavelength anomalous dispersion (MAD) methods. The oligonucleotide crystallizes in space group P2(1)2(1)2(1) with a = 17.97, b = 30.98, c = 44.85 A, alpha = beta = gamma 90 degrees . Data to a resolution of 1.65 A were collected at four wavelengths about the K-absorption edge of the bromine atom (lambda(1) = 0.9323 A, a reference wavelength at the long-wavelength side of the edge; lambda(2) = 0.9192 A, at the absorption-edge inflection point; lambda(3) = 0.9185 A, at the ;white line' absorption maximum; lambda(4) = 0.8983 A, a reference wavelength at the short-wavelength side) using synchrotron radiation at Station PX9.5, SRS, Daresbury. Multiwavelength data could be collected on a single-crystal as the sample was radiation stable. Anomalous and dispersive Patterson maps were readily interpretable to give the bromine anomalous scatterer positions. Phase calculations to 1.65 A, resolution, using all four wavelengths, gave a figure of merit of 0.825 for 2454 reflections. The electron-density map was readily interpretable showing excellent connectivity for the sugar/phosphate backbone and each base was easily characterized. The two nucleotide strands paired up as expected in an antiparallel Watson-Crick-type manner. The structure was refined to 1.65 A using all the data (R-factor = 17.0% based on 3151 reflections, with a data-to-parameter ratio of 2.6). In addition to the four-wavelength analysis, a variety of other phasing strategies, and the associated quality of the resulting electron-density maps, were compared. These included use of either of the reference wavelength data sets in the two possible three-wavelength phasing combinations to assess their relative effectiveness. Moreover, the time dependence upon measuring the Bijvoet differences and its effect upon phasing was also investigated. Finally, the use of only two wavelengths, including Friedel pairs, is demonstrated (the theoretical minimum case); this is of particular interest when considering overall beam time needs and is clearly a feasible experimental strategy, as shown here.

show abstract

“…Intensities in one quadrant from co/20 stepscans, fixed widths A2tg= 3.0 ° for sin0/2 < 0.40/~-~; A20= (1.48 + 3.1 ltan0) ° for 0.4 < sin0/2 < 0.69/~-~; points in scans: 59-87; count time/ point: ~_ 1.9 s as determined by preset monitor count of direct beam; two reflections monitored at ~3 h intervals, intensities constant within 2%; number of observations (including standards): 843 (15 K), 878 (60 K), 1007 (123 K), with ~,scans for 004 at 60 K and 002 at 123 K, and space-group-extinguished reflections (sin0/2 < 0.40/~-~) at 123 K. Background (B) taken as first and last tenths of each scan, thus cr2(I)=I+ 5B; absorption corrections by analytical procedure (de Meulenaer & Tompa, 1965;Templeton & Templeton, 1973), mass absorption 2643 mmZg -I for bound hydrogen (McMullan & Koetzle, 1979), linear absorption 1.979cm -i. Minimum and maximum transmission: 0.76 and 0.93; non-symmetryrelated reflections for refinement: 807 (15 K), 805 (60 K), 815 (123 K); of these 12 (15 K), 20 (60K) and 37 (123 K) had Fo z < 0.0.…”

Section: Methodsmentioning

confidence: 99%

Crystal structure of 1-methyluracil from neutron diffraction at 15, 60 and 123 K

McMullan¹,

Craven²

1989

Acta Crystallogr Sect B

View full text Add to dashboard Cite

show abstract

K-edge anomalous scattering in rubidium hydrogen tartrate

Abstract: Anomalous X‐ray scattering terms for Rb+ near the K‐edge measured in diffraction experiments with synchrotron radiation range up to 4.71 (6) for f′′ and down to −9.80 (11) for f′, in agreement with values derived from the absorption spectrum.

Cited by 10 publications

References 6 publications

Electrostatic properties of β-cytidine and cytosine monohydrate from Bragg diffraction

Electrostatic properties of β-cytidine and cytosine monohydrate from Bragg diffraction

MAD Phasing Strategies Explored with a Brominated Oligonucleotide Crystal at 1.65Å Resolution

Crystal structure of 1-methyluracil from neutron diffraction at 15, 60 and 123 K

Contact Info

Product

Resources

About