scholarly journals X-ray Fiber Diffraction and Computational Analyses of Stacked Hexads in Supramolecular Polymers: Insight into Self-Assembly in Water by Prospective Prebiotic Nucleobases

2021 ◽  
Author(s):  
Asem Alenaizan ◽  
Carlos H. Borca ◽  
Suneesh C. Karunakaran ◽  
Amy K. Kendall ◽  
Gerald Stubbs ◽  
...  
Keyword(s):  
Self Assembly ◽  
Supramolecular Polymers ◽  
X Ray ◽  
Fiber Diffraction ◽  
Computational Analyses ◽  
Insight Into

R factors in X-ray fiber diffraction. III. Asymptotic approximations to largest likely R factors

1990 ◽  
Vol 46 (1) ◽  
pp. 68-72 ◽  
Author(s):  
R. P. Millane
Keyword(s):  
Asymptotic Approximations ◽  
X Ray ◽  
Fiber Diffraction ◽  
Structure Determinations ◽  
R Factors ◽  
Insight Into

The largest likely R factor is useful for evaluating the significance of R factors obtained in structure determinations, and is smaller in fiber diffraction than in traditional crystallography. Very simple approximations to functions used to calculate the largest likely R factor in fiber diffraction are derived. For example, the largest R factor (R m) for m overlapping terms is very well approximated by Rm ≃ (2/π)1/2 m -1/2. These are a useful alternative to the exact, but quite complicated, expressions derived previously. More significantly, they provide insight into the behavior of R factors in fiber diffraction and may be useful in further analysis.

Hydrogen bonded supramolecular structures: a further insight into the diamine-diol recognition and self-assembly

2000 ◽  
Vol 78 (6) ◽  
pp. 723-731 ◽  
Author(s):  
Stefano Roelens ◽  
Paolo Dapporto ◽  
Paola Paoli
Keyword(s):  
Molecular Recognition ◽  
Gas Phase ◽  
Self Assembly ◽  
Supramolecular Assembly ◽  
Supramolecular Structures ◽  
Unique Role ◽  
X Ray ◽  
Molecular Code ◽  
Insight Into

A new H-bonded supramolecular assembly of the diamine-diol family has been obtained from (1R,2R)-1,2-diaminocyclohexane (DAC) and (S)-1-phenyl-1,2-ethanediol (PED). The structure was characterized by single-crystal X-ray analysis and showed the typical architecture of DAC based assemblies, consisting of a three-stranded helicate coiling around a H-bonded core, with a predictable helicity sense determined by the configuration of DAC. The new assembly, while reconfirming the unique role of DAC as a powerful assembler of supramolecular structures, demonstrated that the C2 symmetry of diol partners employed so far is not essential for assembling helicates, although chirality is. In the case of the adduct between (1R,2R)-1,2-diaminocyclohexane and (2R,3R)-2,3-butanediol, molecular recognition and self-assembly have been shown to take place even in the absence of solvent, in the gas phase, where long crystals were formed by spontaneous organized aggregation of diamine-diol units. A thorough analysis of the results from the present and previous investigations has lead to a deeper understanding of the key features of the diamine-diol molecular code and of the requirements for recognition and assembly.Key words: supramolecular, hydrogen bonding, molecular recognition, self-assembly, diamines, diols.

Supramolecular self-assembly of chiral helical tubular polymers with amplified circularly polarized luminescence

2020 ◽  
Vol 4 (9) ◽  
pp. 2772-2781
Author(s):  
Xianhui Tang ◽  
Dandan Chu ◽  
Hong Jiang ◽  
Wei Gong ◽  
Chao Jiang ◽  
...  
Keyword(s):  
Single Crystal ◽  
Self Assembly ◽  
Supramolecular Polymers ◽  
Circularly Polarized ◽  
X Ray ◽  
Circularly Polarized Luminescence ◽  
Polarized Luminescence

Two chiral tubular supramolecular polymers with amplified CPL that can be rationalized by single-crystal X-ray structures are demonstrated.

Structural Insight into the Self-Assembly of a Pharmaceutically Optimized Insulin Analogue Obtained by Small-Angle X-ray Scattering

2020 ◽  
Vol 17 (8) ◽  
pp. 2809-2820
Author(s):  
Lasse Sander Dreyer ◽  
Jesper Nygaard ◽  
Leila Malik ◽  
Thomas Hoeg-Jensen ◽  
Rasmus Høiberg-Nielsen ◽  
...  
Keyword(s):  
Small Angle ◽  
Self Assembly ◽  
Insulin Analogue ◽  
The Self ◽  
X Ray ◽  
X Ray Scattering ◽  
Structural Insight ◽  
Insight Into ◽  
Ray Scattering

Morphological orders of spherulitic crystal textures in Belousov–Zhabotinsky-type oscillatory reaction system

2015 ◽  
Vol 69 (4) ◽  
Author(s):  
Narendra Yadav ◽  
Syam Sundar Majhi ◽  
Sudhir Kumar Saw ◽  
Prem Kumar Srivastava
Keyword(s):  
Self Assembly ◽  
Reaction System ◽  
Nucleation Mechanism ◽  
Oscillatory Reaction ◽  
X Ray Diffraction ◽  
Growth Behaviour ◽  
Large Crystal ◽  
X Ray ◽  
Crystal Phases ◽  
Insight Into

AbstractThe morphological orders of spherulitic crystal patterns in a Belousov-Zhabotinsky-type oscillatory reaction system were studied. The experiments showed that the morphology of crystal patterns were highly dependent on the reaction temperature. The reaction was initially carried out at 30°C, leading to the growth of multi-centred spherulitic patterns. The single-centred spherulitic patterns with fairly large crystal fibrils were obtained at 35°C. A number of undersized crystal assemblies with fractal geometry were also investigated at 25°C. The gross morphology of the crystal patterns was examined using optical microscopy and a scanning electron microscope which revealed the fibrous organisations. A particle-mediated self-assembly scheme was proposed for the growth of the spherulitic patterns. The insight into the nucleation mechanism, growth behaviour, and morphological orders of the growing patterns is discussed in detail. The crystal phases, ordering of textures, and composition of the crystals were characterised by thermal and X-ray diffraction techniques

Quantitative Analysis Of X-Ray Images From Geological Materials

1990 ◽  
Vol 48 (2) ◽  
pp. 244-245
Author(s):  
J. M. Paque ◽  
R. Browning ◽  
P. L. King ◽  
P. Pianetta
Keyword(s):  
Quantitative Analysis ◽  
Bulk Composition ◽  
Principal Component ◽  
Analytical Description ◽  
Bulk Sample ◽  
Geological Samples ◽  
X Ray ◽  
Software And Hardware ◽  
And Storage ◽  
Insight Into

Geological samples typically contain many minerals (phases) with multiple element compositions. A complete analytical description should give the number of phases present, the volume occupied by each phase in the bulk sample, the average and range of composition of each phase, and the bulk composition of the sample. A practical approach to providing such a complete description is from quantitative analysis of multi-elemental x-ray images.With the advances in recent years in the speed and storage capabilities of laboratory computers, large quantities of data can be efficiently manipulated. Commercial software and hardware presently available allow simultaneous collection of multiple x-ray images from a sample (up to 16 for the Kevex Delta system). Thus, high resolution x-ray images of the majority of the detectable elements in a sample can be collected. The use of statistical techniques, including principal component analysis (PCA), can provide insight into mineral phase composition and the distribution of minerals within a sample.

In situ Time-Resolved Small-Angle X-ray Scattering Reveals the Formation Kinetics of Polyelectrolyte Complex Micelles

2019 ◽  
Author(s):  
Hao Wu ◽  
Jeffrey Ting ◽  
Siqi Meng ◽  
Matthew Tirrell
Keyword(s):  
Small Angle ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Polyelectrolyte Complex ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

We have directly observed the <i>in situ</i> self-assembly kinetics of polyelectrolyte complex (PEC) micelles by synchrotron time-resolved small-angle X-ray scattering, equipped with a stopped-flow device that provides millisecond temporal resolution. This work has elucidated one general kinetic pathway for the process of PEC micelle formation, which provides useful physical insights for increasing our fundamental understanding of complexation and self-assembly dynamics driven by electrostatic interactions that occur on ultrafast timescales.

Copper–oxygen Dynamics in Tyrosinase

2019 ◽  
Author(s):  
Nobutaka Fujieda ◽  
Sachiko Yanagisawa ◽  
Minoru Kubo ◽  
Genji Kurisu ◽  
Shinobu Itoh
Keyword(s):  
Catalytic Mechanism ◽  
Substrate Binding ◽  
Active Form ◽  
Copper Ion ◽  
Atomic Resolution ◽  
Oxygen Species ◽  
X Ray ◽  
Oxygen Dynamics ◽  
Insight Into ◽  
Copper Centre

To unveil the activation of dioxygen on the copper centre (Cu<sub>2</sub>O<sub>2</sub>core) of tyrosinase, we performed X-ray crystallograpy with active-form tyrosinase at near atomic resolution. This study provided a novel insight into the catalytic mechanism of the tyrosinase, including the rearrangement of copper-oxygen species as well as the intramolecular migration of copper ion induced by substrate-binding.<br>

scholarly journals Self-Assembled Bimetallic Aluminum-Salen Catalyst for the Cyclic Carbonates Synthesis

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4097
Author(s):  
Wooyong Seong ◽  
Hyungwoo Hahm ◽  
Seyong Kim ◽  
Jongwoo Park ◽  
Khalil A. Abboud ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Self Assembly ◽  
Reaction Pathway ◽  
Kinetic Studies ◽  
Cyclic Carbonate ◽  
Reaction Conditions ◽  
Formation Reaction ◽  
X Ray ◽  
Carbonate Formation ◽  
Salen Aluminum

Bimetallic bis-urea functionalized salen-aluminum catalysts have been developed for cyclic carbonate synthesis from epoxides and CO2. The urea moiety provides a bimetallic scaffold through hydrogen bonding, which expedites the cyclic carbonate formation reaction under mild reaction conditions. The turnover frequency (TOF) of the bis-urea salen Al catalyst is three times higher than that of a μ-oxo-bridged catalyst, and 13 times higher than that of a monomeric salen aluminum catalyst. The bimetallic reaction pathway is suggested based on urea additive studies and kinetic studies. Additionally, the X-ray crystal structure of a bis-urea salen Ni complex supports the self-assembly of the bis-urea salen metal complex through hydrogen bonding.

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