scholarly journals Adsorption of PTCDA and C60 on KBr(001): electrostatic interaction versus electronic hybridization

2016 ◽  
Vol 18 (16) ◽  
pp. 11008-11016 ◽  
Author(s):  
Qian Jia ◽  
Zhi-Xin Hu ◽  
Wei Ji ◽  
Sarah A. Burke ◽  
Hong-Jun Gao ◽  
...  
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Electrostatic Interaction ◽  
Density Variation ◽  
Electrostatic Attraction ◽  
Aromatic Molecules ◽  
Electron Density Variation ◽  
Interaction Versus ◽  
Primary Interaction

A plot of differential charge density shows opposite electron density variation in two slabs near PTCDA and KBr(001), revealing electrostatic attraction as the primary interaction between aromatic molecules and insulator substrates.

A Biological System Producing a Self-Assembling Cholesteric Protein Liquid Crystal

1971 ◽  
Vol 8 (1) ◽  
pp. 93-109
Author(s):  
A. C. NEVILLE ◽  
B. M. LUKE
Keyword(s):  
Liquid Crystal ◽  
Electron Density ◽  
Electron Micrographs ◽  
Self Assembly ◽  
Liquid Crystalline ◽  
Density Variation ◽  
Self Assembling ◽  
The Matrix ◽  
Electron Density Variation ◽  
Helicoidal Structure

The protein in the oothecal glands of praying mantids (Sphodromantis tenuidentata, Miomantis monacha) exists in the form of lamellar liquid crystalline spherulites, which coalesce as they flow out of a punctured gland tubule. Electron micrographs of sections of these spherulites after fixation show parabolic patterns of an electron-light component, set in a continuous matrix of protein. Such patterns arise in helicoidal systems (e.g. arthropod cuticle) and microdensitometric scans of the matrix show a rhythmical electron-density variation consistent with helicoidal structure. Double spiral patterns identical to those seen in liquid crystal spherulites are illustrated. These properties resemble those of cholesteric liquid crystals. The constructional units appear to be molecular rather than fibrillar as described by previous authors. The helicoidal architecture arises by self-assembly in the gland lumen. Lamellar surface structures self-assembled spontaneously on glass coverslips when the protein was left to stand for several days. When heated to 55 °C, the birefringent liquid crystalline protein abruptly changes to an isotropic gel, with associated loss of parabolic patterning in electron micrographs and of the rhythmical electron-density variation on microdensitometric scans. This behaviour is compared to the formation of gelatin from collagen, in terms of the randomization of an originally ordered secondary structure.

scholarly journals Investigation of the Electron Density Variation During the 21 August 2017 Solar Eclipse

2018 ◽  
Vol 45 (3) ◽  
pp. 1253-1261 ◽  
Author(s):  
B. W. Reinisch ◽  
P. B. Dandenault ◽  
I. A. Galkin ◽  
R. Hamel ◽  
P. G. Richards
Keyword(s):  
Electron Density ◽  
Solar Eclipse ◽  
Density Variation ◽  
Electron Density Variation

scholarly journals Charge density studies of interactions in macromolecules – the case of sunitinib

2014 ◽  
Vol 70 (a1) ◽  
pp. C970-C970
Author(s):  
Maura Malińska ◽  
Katarzyna Jarzembska ◽  
Anna Goral ◽  
Andrzej Kutner ◽  
Krzysztof Woźniak ◽  
...  
Keyword(s):  
Charge Density ◽  
Interaction Energy ◽  
Electron Density ◽  
Electrostatic Interaction ◽  
Tyrosine Kinases ◽  
Electrostatic Interactions ◽  
Kinase Inhibitor ◽  
Topological Analysis ◽  
3D Structure ◽  
X Ray

Electron density is a key factor in determining properties of molecules. Knowledge of the electron density distribution allows to determine not only the 3D structure of molecules, but also various one-electron properties (electric moments, electrostatic potential, electrostatic interaction energy, etc.). X-ray diffraction is a great tool for obtaining this kind of information. For macromolecules, however, quantitative determination of charge density from experiment is possible on rare occasions only. We will present that with the University at Buffalo pseudoatom database (UBDB) approach [1,2] it is now possible to reconstruct electron density of any macromolecular system for which atomic coordinates are available. The approach is fast and opens an excellent opportunity to investigate macromolecular complexes by means of topological analysis of electron density (and derivatives thereof), electrostatic interaction energy analysis, and many others. The results of our studies on sunitinib (SU) will illustrate the possibilities of the approach. SU is an inhibitor of tyrosine kinases and was approved as a drug in 2006. Comprehensive analysis of the SU malate crystal and SU complexes with a series of protein kinases was carried out. The high resolution single crystal X-ray measurement and UBDB approach served as the basis for the reconstruction of the charge density of SU and the protein complexes. Hirshfeld surface and topological analyses revealed a similar interaction pattern in the SU malate crystal to that in the protein binding pockets. SU forms nine preserved bond paths corresponding to hydrogen bonds and also to the C-H...O and C-H...π contacts common for all analyzed kinases. It interacts typically with similar electrostatic interaction energy with the studied proteins and can adjust its conformation to fit the binding pocket in a way to enhance the electrostatic interactions. Such behavior can be responsible for a broad spectrum of action of SU as kinase inhibitor.

scholarly journals Enhanced Radio Source Scintillation due to Comet Austin (1989c1)

1991 ◽  
Vol 44 (5) ◽  
pp. 565 ◽  
Author(s):  
P Janardhan ◽  
SK Alurkar ◽  
AD Bobra ◽  
OB Slee
Keyword(s):  
Solar Wind ◽  
Radio Source ◽  
Electron Density ◽  
Density Variation ◽  
Scintillation Index ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
Electron Density Variation ◽  
Comet Halley

Enhanced scintillations in the direction of the quasar 2204+29 (3C441) were observed on 13 May 1990 when the tail of Comet Austin passed in front of it. Comparison with previous observations at 103, 327 and 408 MHz of Comet Halley and at 408 MHz of Comet Wilson show that proper occultation geometry is essential for observing enhanced scintillations. It has been shown that the solar elongation ? during such observations should be large, typically greater than 60� and in no case less than 30� at 103 MHz. At the time of the occultation the scintillation index (r.m.s./mean source flux) was greater than that expected for this source by a factor of 3. The r.m.s. electron density variation /IN, at a distance of 0�9 A.U. from the sun and 7�3� downstream of the nucleus, was found to be 6 cm-3 as compared with 1 cm-3 for the normal solar wind at 1 A.U. The corresponding scale sizes of the turbulence were found to be much finer than normally found in interplanetary scintillation (IPS) caused by the solar wind.

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