Treatment of the Normal Vibrations of Helical Polymers; Methods for Factoring the B Matrix and for Calculating Atomic Displacements

1967 ◽  
Vol 47 (6) ◽  
pp. 2034-2039 ◽  
Author(s):  
Hiromu Sugeta ◽  
Tatsuo Miyazawa
Keyword(s):  
Normal Vibrations ◽  
Helical Polymers ◽  
Atomic Displacements

RNA polymerase: Preparation and structural analysis of helical polymers

1984 ◽  
Vol 42 ◽  
pp. 152-153
Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi
Keyword(s):  
Structural Analysis ◽  
Rna Polymerase ◽  
Molecular Level ◽  
X Ray Diffraction ◽  
Helical Polymers ◽  
X Ray ◽  
E Coli ◽  
The Past ◽  
Ordered Arrays ◽  
Low Ionic Strength

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.

Symmetry breaking in convergent-beam diffraction

1989 ◽  
Vol 47 ◽  
pp. 480-481
Author(s):  
D.J. Eaglesham
Keyword(s):  
Symmetry Breaking ◽  
Point Group ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
Space Groups ◽  
Atomic Displacements ◽  
Small Probe ◽  
Phase Sensitive ◽  
Convergent Beam

Convergent Beam Electron Diffraction is now almost routinely used in the determination of the point- and space-groups of crystalline samples. In addition to its small-probe capability, CBED is also postulated to be more sensitive than X-ray diffraction in determining crystal symmetries. Multiple diffraction is phase-sensitive, so that the distinction between centro- and non-centro-symmetric space groups should be trivial in CBED: in addition, the stronger scattering of electrons may give a general increase in sensitivity to small atomic displacements. However, the sensitivity of CBED symmetry to the crystal point group has rarely been quantified, and CBED is also subject to symmetry-breaking due to local strains and inhomogeneities. The purpose of this paper is to classify the various types of symmetry-breaking, present calculations of the sensitivity, and illustrate symmetry-breaking by surface strains.CBED symmetry determinations usually proceed by determining the diffraction group along various zone axes, and hence finding the point group. The diffraction group can be found using either the intensity distribution in the discs

scholarly journals Dinuclear Species versus Zigzag or Helical Polymers in Palladium, Zinc, and Copper Complexes with Ditopic Bis(pyrazolyl)methane Ligands

2013 ◽  
Vol 2013 (35) ◽  
pp. 5930-5930
Author(s):  
Gema Durá ◽  
M. Carmen Carrión ◽  
Félix A. Jalón ◽  
Blanca R. Manzano ◽  
Ana M. Rodríguez
Keyword(s):  
Copper Complexes ◽  
Helical Polymers

Synthesis of Helical Polymers by Polycondensation of Diboronic Acid and Chiral Tetrols

1995 ◽  
Vol 24 (7) ◽  
pp. 603-604 ◽  
Author(s):  
Masafumi Mikami ◽  
Seiji Shinkai
Keyword(s):  
Helical Polymers

scholarly journals Interactions of Ruddlesden-Popper Phases and Migration-Induced Field-Stabilized Polar Phase in Strontium Titanate

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 693
Author(s):  
Christian Ludt ◽  
Elena Ovchinnikova ◽  
Anton Kulikov ◽  
Dmitri Novikov ◽  
Sibylle Gemming ◽  
...  
Keyword(s):  
Strontium Titanate ◽  
Density Functional ◽  
Surface Region ◽  
Point Of View ◽  
Polar Phase ◽  
Near Surface ◽  
Atomic Displacements ◽  
Induced Field ◽  
And Migration ◽  
Novel Concept

This work focuses on the validation of a possible connection of the known Ruddlesden-Popper (RP) phases and the novel concept of the migration-induced field-stabilized polar (MFP) phase. To study this subject, model structures of RP phases in bulk strontium titanate are analyzed by means of density functional theory (DFT). The obtained geometries are compared to experimental MFP data. Good agreement can be found concerning atomic displacements in the pm range and lattice strain inferred by the RP phases. Looking at the energy point of view, the defect structures are on the convex hull of the Gibb’s free energy. Although the dynamics to form the discussed defect models are not addressed in detail, the interplay and stability of the described defect model will add to the possible structure scenarios within the near-surface region of strontium titanate. As a result, it can be suggested that RP phases generally favor the MFP formation.

The chemical bond and atomic displacements in SrTiO3 from X-ray diffraction analysis

1995 ◽  
Vol 51 (6) ◽  
pp. 942-951 ◽  
Author(s):  
Yu. A. Abramov ◽  
V. G. Tsirelson ◽  
V. E. Zavodnik ◽  
S. A. Ivanov ◽  
Brown I. D.
Keyword(s):  
Diffraction Analysis ◽  
Chemical Bond ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Displacements
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