scholarly journals Selectivity of cations and nonelectrolytes for acetylcholine-activated channels in cultured muscle cells.

1978 ◽  
Vol 71 (4) ◽  
pp. 397-410 ◽  
Author(s):  
L Y Huang ◽  
W A Catterall ◽  
G Ehrenstein
Keyword(s):  
Hydrogen Bond ◽  
Positive Charge ◽  
Binding Capacity ◽  
High Mobility ◽  
Muscle Cells ◽  
The Other ◽  
Organic Cations ◽  
Hydrogen Binding ◽  
Alkali Cations ◽  
Charged Site

The selectivity of acetylcholine (A-Ch)-activated channels for alkali cations, organic cations, and nonelectrolytes in cultured muscle cells has been studied. To test the effect of size, charge, and hydrogen-binding capacity of permeant molecules on their permeability, we have obtained the selectivity sequences of alkali cations, compared the permeability of pairs of permeant molecules with similar size and shape but differing in charge, and studied the permeability of amines of different hydrogen bonding capacity. ACh-activated channels transport alkali cations of small hydration radii and high mobility. The molecules with positive charge and (or) a hydrogen-bond donating moiety are more permeable than the ones without. On the other hand, several nonelectrolytes, i.e., ethylene glycol, formamide, and urea, do have a small, but measurable, permeability through the channels. These results are consistent with a model that ACh-activated channel is a water-filled pore containing dipoles or hydrogen bond accepting groups and a negative charged site with a pK of 4.8.

A Hydrogen Bond Between Linear Tetrapyrrole and Conserved Aspartate Causes the Far-Red Shifted Absorption of Phytochrome Photoreceptors

2020 ◽  
Author(s):  
Egle Maximowitsch ◽  
Tatiana Domratcheva
Keyword(s):  
Hydrogen Bond ◽  
Light Adaptation ◽  
Positive Charge ◽  
Pyrrole Ring ◽  
Md Simulations ◽  
Spectral Shift ◽  
Specific Domain ◽  
Study Guides ◽  
Rational Engineering ◽  
Tuning Mechanism

Photoswitching of phytochrome photoreceptors between red-absorbing (Pr) and far-red absorbing (Pfr) states triggers light adaptation of plants, bacteria and other organisms. Using quantum chemistry, we elucidate the color-tuning mechanism of phytochromes and identify the origin of the Pfr-state red-shifted spectrum. Spectral variations are explained by resonance interactions of the protonated linear tetrapyrrole chromophore. In particular, hydrogen bonding of pyrrole ring D with the strictly conserved aspartate shifts the positive charge towards ring D thereby inducing the red spectral shift. Our MD simulations demonstrate that formation of the ring D–aspartate hydrogen bond depends on interactions between the chromophore binding domain (CBD) and phytochrome specific domain (PHY). Our study guides rational engineering of fluorescent phytochromes with a far-red shifted spectrum.

scholarly journals The Properties of Cu Ions in Zeolites CuY Studied by IR Spectroscopy

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4686
Author(s):  
Jerzy Podobiński ◽  
Mariusz Gackowski ◽  
Grzegorz Mordarski ◽  
Katarzyna Samson ◽  
Michał Śliwa ◽  
...  
Keyword(s):  
Ir Spectroscopy ◽  
Positive Charge ◽  
Co Adsorption ◽  
The Other ◽  
Probe Molecules ◽  
Adsorption And Desorption ◽  
Other Hand ◽  
Close Proximity ◽  
No And Co Adsorption ◽  
Cu Ions

The properties of both Cu2+ and Cu+ ions in zeolite CuY were followed with NO and CO as probe molecules. Cu2+ was found to be located in SII, SII*, and SIII sites, whereas Cu+ was found in SII and SII* sites. The fine analysis of the spectra of Cu2+-NO and Cu+-CO adducts suggests that both in SII and in SII* sites two kinds of Cu cations exist. They differ in the positive charge, which may be related to the varying numbers of AlO4− in close proximity. The experiments of NO and CO adsorption and desorption evidenced that both Cu2+ and Cu+ sites of highest positive charge bind probe molecules most strongly but activate them to a lesser extent than the Cu sites of lowest positive charge. The experiments of reduction with hydrogen evidenced that the Cu ions of higher positive charge are first reduced by hydrogen. On the other hand, Cu sites of the lowest positive charge are first oxidized by oxygen. The experiments with CuNaY zeolites of various Cu contents suggest that the first introduced Cu (at low Cu contents) created Cu+, which was the most neutralized by framework oxygens. Such Cu cations are the most stabilized by framework oxygens.

Intercalation Processes in Cobalt Substituted Nickel Oxyhydroxides

1990 ◽  
Vol 210 ◽  
Author(s):  
Claude Delmas
Keyword(s):  
Ir Spectroscopy ◽  
Mechanical Treatment ◽  
Positive Charge ◽  
Van Der Waals ◽  
The Other ◽  
Hydrolysis Reaction ◽  
Water Molecules ◽  
Layered Oxides ◽  
Experimental Conditions ◽  
Cobalt Ions

AbstractChimie douce reactions (hydrolysis and reduction) from layered oxides : NaNiO2, NaxCoO2 and NaNil-xCoxO2 lead to numerous oxyhydroxides and hydroxides which differ by the composition of the intersheet space.According to the experimental conditions of the hydrolysis reaction, the oxyhydroxides can be unhydrated or intercalated with one or two layers of water molecules. From the most hydrated phases, the other ones can be obtained by chemical, thermal and even mechanical treatment.The reduction of Co-substituted nickel oxyhydroxides leads to hydroxides in which nickel and cobalt ions are respectively divalent and trivalent. In order to compensate the excess of positive charge in the (Ni, Co)O2 sheet, anions (OH-, CO32-, SO42-, NO3-) are inserted in the Van der Waals gap.For the highest anion amounts, well ordered α*-type materials are obtained. Water molecules are simultaneously inserted in the interslab space. Their structure is strongly related to the hydrotalcite one. When the amouit of anions in the intersheet space is not sufficient, interstratified materials are obtained. In this case the (Ni,Co)(OH)2 slabs are separated by a layer of CO32- anions and water molecules (α*-type) or by an empty Van der Waals gap (β(II)-type). The amount of α*-type planes in the structure increases with the cobalt amount. All these materials have been characterized by IR spectroscopy which allows to detect the existence of two types of O-H bonds (free in α*-type plane or hydrogen bonded in ²(II)-type plane).

Paranemin and the organization of desmin filament networks

2001 ◽  
Vol 114 (6) ◽  
pp. 1079-1089 ◽  
Author(s):  
S.C. Schweitzer ◽  
M.W. Klymkowsky ◽  
R.M. Bellin ◽  
R.M. Robson ◽  
Y. Capetanaki ◽  
...  
Keyword(s):  
Cell Lines ◽  
Intermediate Filament ◽  
Transgene Expression ◽  
De Novo ◽  
Muscle Cells ◽  
The Other ◽  
Intermediate Filament Proteins ◽  
Mouse Fibroblasts ◽  
Filament Networks ◽  
Filament Network

De novo expression of vimentin, GFAP or peripherin leads to the assembly of an extended intermediate filament network in intermediate filament-free SW13/cl.2 cells. Desmin, in contrast, does not form extended filament networks in either SW13/cl.2 or intermediate filament-free mouse fibroblasts. Rather, desmin formed short thickened filamentous structures and prominent spot-like cytoplasmic aggregates that were composed of densely packed 9–11 nm diameter filaments. Analysis of stably transfected cell lines indicates that the inability of desmin to form extended networks is not due to a difference in the level of transgene expression. Nestin, paranemin and synemin are large intermediate filament proteins that coassemble with desmin in muscle cells. Although each of these large intermediate filament proteins colocalized with desmin when coexpressed in SW-13 cells, expression of paranemin, but not synemin or nestin, led to the formation of an extended desmin network. A similar rescue of desmin network organization was observed when desmin was coexpressed with vimentin, which coassembles with desmin, or with keratins, which formed a distinct filament network. These studies demonstrate that desmin filaments differ in their organizational properties from the other vimentin-like intermediate filament proteins and appear to depend upon coassembly with paranemin, at least when they are expressed in non-muscle cells, in order to form an extended filament network.

Mast cells and histamine concentration in muscle and liver of dystrophic mice

1964 ◽  
Vol 206 (2) ◽  
pp. 338-340 ◽  
Author(s):  
Pierre Bois
Keyword(s):  
Mast Cells ◽  
Histidine Decarboxylase ◽  
Binding Capacity ◽  
The Other ◽  
Decarboxylase Activity ◽  
Histamine Concentration ◽  
Other Hand ◽  
Histamine Binding ◽  
Dystrophic Mice ◽  
Histidine Decarboxylase Activity

The distribution of mast cells in muscle and liver of dystrophic mice was studied; histamine and histidine decarboxylase activity was also measured in the same tissues. Mast cells were significantly more numerous in dystrophic muscles. On the other hand, very few cells could be counted in the liver of either control or dystrophic animals. Histamine concentration was higher in muscle and liver of dystrophic mice; no visible increase in histidine decarboxylase activity could be measured by the methods used. It is concluded that histamine-binding capacity is increased in some tissues of dystrophic mice.

On the Nature of Weak Spots in High-k Layers Submitted to Anneals

2004 ◽  
Vol 811 ◽  
Author(s):  
J. Pétry ◽  
W. Vandervorst ◽  
O. Richard ◽  
T. Conard ◽  
P. DeWolf ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Strong Correlation ◽  
Positive Charge ◽  
The Other ◽  
Physical Analysis ◽  
Force Microscopy ◽  
Atomic Force ◽  
Other Hand ◽  
High K ◽  
High K Dielectric

ABSTRACTIn the path to the introduction of high-k dielectric into IC components, a large number of challenges have still to be solved. Some of the major issues concern the low mobility of carriers and the reliability of the devices. Trapped charges in the stack have been identified as being the cause of these issues. With this in mind, we used Conducting Atomic Force Microscopy, combined with physical analysis to understand the nature of these charges. In this contribution, we have studied the uniformity of thin HfO2 layers, with and without anneal. The Conducting Atomic Force microscopy measurements show spots of higher conductivity. Recording local IV's in those ‘weak’ spots suggests that they consist of positive charge. On the other hand, XPS and ToFSIMS analysis show a diffusion of the interfacial SiO2 upwards into the high-k layer. Finally, the comparison of samples with differing high-k material and crystallinity indicates a strong correlation between the weak spots and the presence of silicon in the film.

scholarly journals N-(4-Ethoxy-2,5-dinitrophenyl)acetamide

IUCrData ◽  
2020 ◽  
Vol 5 (8) ◽  
Author(s):  
Sannihith N. Uppu ◽  
Ogad A. Agu ◽  
Curtistine J. Deere ◽  
Frank R. Fronczek
Keyword(s):  
Hydrogen Bond ◽  
Nitro Group ◽  
Benzene Ring ◽  
Title Compound ◽  
The Other ◽  
Ring Plane ◽  
Torsion Angles ◽  
Compound C ◽  
Bifurcated Hydrogen Bond

In the title compound, C10H11N3O6, the torsion angles about the bonds to the benzene ring are less than 4°, except for the nitro groups, which are twisted out of the ring plane by 25.27 (3) and 43.63 (2)°. The N—H group forms a bifurcated hydrogen bond, with an intramolecular component to a nitro group O atom and an intermolecular component to the other nitro group, thereby forming chains propagating in the [010] direction. Several weak C—H...O interactions are also present.

(1R*,5R*,7R*,8S*)-3-(3,4-Dihydroxybenzoyl)-4-hydroxy-8-methyl-1,5,7-tris(3-methyl-2-butenyl)-8-(4-methyl-3-pentenyl)bicyclo[3.3.1]non-3-ene-2,9-dione

2007 ◽  
Vol 63 (3) ◽  
pp. o1282-o1284 ◽  
Author(s):  
Bruno Ndjakou Lenta ◽  
Diderot Tchamo Noungoue ◽  
Krishna Prasad Devkota ◽  
Patrice Aime Fokou ◽  
Silvere Ngouela ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Medicinal Plant ◽  
Chair Conformation ◽  
The Other ◽  
Aryl Group ◽  
One Dimensional ◽  
Compound C ◽  
Bicyclic System ◽  
Symphonia Globulifera

The title compound, C38H50O6, also known as guttiferone A, was isolated from the medicinal plant Symphonia globulifera. It is a benzophenone derivative where one aryl group is derivatized to give a bicyclic system which has two prenyl groups attached to the bridgehead. One of the cyclohexane rings in the bicyclic system is in a chair form, while the other has a distorted half-chair conformation. In addition to an intramolecular O—H...O hydrogen bond, intermolecular O—H...O hydrogen bonds link molecules into one-dimensional chains.

Understanding distortions of inorganic substructures in chloridobismuthates(III)

2021 ◽  
Vol 77 (5) ◽  
Author(s):  
Maciej Bujak
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Inorganic Anions ◽  
Cambridge Structural Database ◽  
Molar Ratio ◽  
Organic Cations ◽  
Hybrid Crystals ◽  
Structural Database ◽  
Distortion Parameters

The molar ratio variations of organic and inorganic reactants of chloridobismuthates(III) with N,N-dimethylethane-1,2-diammonium, [(CH3)2NH(CH2)2NH3]2+, and N,N,N′,N′-tetramethylguanidinium, [NH2C{N(CH3)2}2]+, cations lead to the formation of four different products, namely, tris(N,N-dimethylethane-1,2-diammonium) bis[hexachloridobismuthate(III)], [(CH3)2NH(CH2)2NH3]3[BiCl6]2 (1), catena-poly[N,N-dimethylethane-1,2-diammonium [[tetrachloridobismuthate(III)]-μ-chlorido]], {[(CH3)2NH(CH2)2NH3][BiCl5]} n (2), tris(N,N,N′,N′-tetramethylguanidinium) tri-μ-chlorido-bis[trichloridobismuthate(III)], [NH2C{N(CH3)2}2]3[Bi2Cl9] (3), and catena-poly[N,N,N′,N′-tetramethylguanidinium [[dichloridobismuthate(III)]-di-μ-chlorido]], {[NH2C{N(CH3)2}2][BiCl4]} n (4). The hybrid crystals 1–4, containing relatively large but different organic cations, are composed of four distinct anionic substructures. They are built up from isolated [BiCl6]3− octahedra in 1, from face-sharing bioctahedral [Bi2Cl9]3− units in 3, from polymeric corner-sharing {[BiCl5]2−} n chains in 2 and from edge-sharing {[BiCl4]−} n chains in 4. The distortions shown by the single [BiCl6]3− polyhedra in 1–4 are associated with intrinsic interactions within the anionic substructures and the organic...inorganic substructures interactions, namely, N/C—H...Cl hydrogen bonds. The first factor is the stronger, which is evident in comparison of the experimentally determined geometrical and calculated distortion parameters for the isolated octahedron in 1 to the more complex inorganic substructures in 2–4. The formation of N—H...Cl hydrogen bonds, in terms of their number and strength, is favoured for 1 and 3 containing relatively easily accessed hydrogen-bond acceptors of isolated [BiCl6]3− and [Bi2Cl9]3− units. The studies of the deviations from regularity of the [BiCl6]3− octahedra within inorganic substructures were supported by a survey of the Cambridge Structural Database, which confirmed the role played by different factors in the variations in geometry of the inorganic anions.

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