By X-ray diffraction analysis and IR spectroscopy, it was established here that vinyl carbocations CH/CH with carborane counterion CHBCl form stable monosolvates CH⋅CH/CH⋅CH with molecules of alkenes CH/CH. They contain molecular group =C⋯H-C= with a new type of bond formed by the H atom of the H-C= group of the alkene with the C atom of the C=C group of the carbocation. The short C----C distance, equal to 2.
View Article and Find Full Text PDFThere is a growing interest in glial cells in the central nervous system due to their important role in maintaining brain homeostasis under physiological conditions and after injury. A significant amount of evidence has been accumulated regarding their capacity to exert either pro-inflammatory or anti-inflammatory effects under different pathological conditions. In combination with their proliferative potential, they contribute not only to the limitation of brain damage and tissue remodeling but also to neuronal repair and synaptic recovery.
View Article and Find Full Text PDFIntroduction of Cl and O atoms into C-vinyl carbocations was studied by X-ray diffraction analysis and IR spectroscopy. Chlorine atoms are weak electron acceptors in ordinary molecules but, within vinyl carbocations, manifest themselves as strong electron donors that accept a positive charge. The attachment of a Cl atom directly to a C=C bond leads to an increase in the e-density on it, exceeding that of the common double bond.
View Article and Find Full Text PDFX-ray diffraction analysis and IR spectroscopy were used to study the products of the interaction of vinyl cations CH and CH (Cat) (as salts of carborane anion CHBCl) with basic molecules of water, alcohols, and acetone that can crystallize from solutions in dichloromethane and CHF. Interaction with water, as content increased, proceeded via three-stages. (1) adduct Cat·OH forms in which HO binds (through the O atom) to the C=C bond of the cation with the same strength as seen in the binding to Na in Na(HO).
View Article and Find Full Text PDFIt was found that alkyl carbocations, when their salts are dissolved in common organochlorine solvents, decompose to unsaturated vinyl-type carbocations that are stabler in solutions. This is a convenient method for obtaining salts of vinyl cations and their solutions for further research.
View Article and Find Full Text PDFThe neuronal cell adhesion and recognition molecule L1 does not only 'keep cells together' by way of homophilic and heterophilic interactions, but can also promote cell motility when cleaved into fragments by several proteases. It has largely been thought that such fragments are signs of degradation. Now, it is clear that proteolysis contributes to the pronounced functional diversity of L1, which we have reviewed in this work.
View Article and Find Full Text PDFSolid salts of the divinyl chloronium (CH)Cl cation () and unsaturated CHCl and CH carbocations with the highly stable CHBHal anion (Hal=F, Cl) were obtained for the first time. At 120 °C, the salt of the chloronium cation decomposes, yielding a salt of the CH cation. This thermally stable (up to 200 °C) carbocation is methyl propargyl, CH≡C-C-H-CH (), which, according to quantum chemical calculations, should be energetically much less favorable than other isomers of the CH cations.
View Article and Find Full Text PDFThe butylene carbocation in its salts with anions CHBF and CHBCl forms isomers CH=C-CH-CH () and CH-C=CH-CH (), which were characterized here by infrared (IR) spectroscopy and X-ray diffraction analysis. The strongest influence on the structure of the cations is exerted by geometric ordering of their anionic environment. In the crystalline phase, the cations uniformly interact with neighboring anions, and the C=C bond is located in the middle part of the cations forming a -CH=C- moiety with the highest positive charge on it and the lowest νC=C frequency, at 1490 cm.
View Article and Find Full Text PDFThe nature of brain impairment after hypoxia is complex and recovery harnesses different mechanisms, including neuroprotection and neurogenesis. Experimental evidence suggests that hypoxia may trigger neurogenesis postnatally by influencing the expression of a variety of transcription factors. However, the existing data are controversial.
View Article and Find Full Text PDFThree isomers of the allyl cation CH were obtained in salts with the carborane anion CHBCl . Two of them, angular CH-CH=CH () and linear CH-C=CH (), were characterized by X-ray crystallography, and the third one, (CHCHCH) (), is formed in an amorphous salt. The stretch vibration of the charged double bond C=C of and is decreased by 162 cm () or 76 cm () as compared to that of neutral propene.
View Article and Find Full Text PDFThe isobutylene carbocation (CH)C=CH was obtained in amorphous and crystalline salts with the carborane anion CHBCl . The cation was characterized by X-ray crystallography and IR spectroscopy. Its crystal structure shows a relatively uniform ionic interaction of the cation with the surrounding anions, with a slightly shortened distance between the C atom of the =CH group and the Cl atom of the anion, pointing to a higher positive charge on this group.
View Article and Find Full Text PDFFront Cell Dev Biol
March 2021
The nervous system is highly vulnerable to different factors which may cause injury followed by an acute or chronic neurodegeneration. Injury involves a loss of extracellular matrix integrity, neuronal circuitry disintegration, and impairment of synaptic activity and plasticity. Application of pleiotropic molecules initiating extracellular matrix reorganization and stimulating neuronal plasticity could prevent propagation of the degeneration into the tissue surrounding the injury.
View Article and Find Full Text PDFAn experimental study on protonation of simple weakly basic molecules (L) by the strongest solid superacid, H(CHB F ), showed that basicity of SO is high enough (during attachment to the acidic H atoms at partial pressure of 1 atm) to break the bridged H-bonds of the polymeric acid and to form a mixture of solid mono- LH ⋅⋅⋅An , and disolvates, L-H -L. With a decrease in the basicity of L=CO (via C), N O, and CO (via O), only proton monosolvates are formed, which approach L-H -An species with convergence of the strengths of bridged H-bonds. The molecules with the weakest basicity, such as CO and weaker, when attached to the proton, cannot break the bridged H-bond of the polymeric superacid, and the interaction stops at stage of physical adsorption.
View Article and Find Full Text PDFAdsorption of gaseous NO on the acidic surface Brønsted centers of the strongest known solid acid, H(CHBF), results in formation of the N≡N-OH cation. Its positive charge is localized mainly to the H-atom, which is H-bonded to the CHBF anion forming an asymmetric proton disolvate of the L-HL type, where L = NO and L = CHBF. NO protonation under the same conditions leads to the formation of the highly reactive cation radical NOH˙, which reacts rapidly with an NO molecule according to the equation NOH + NO → [NOH] → NOH + O resulting in the formation of two types of NOH cations: (i) a typical Brønsted superacid, N[triple bond, length as m-dash]N-OH, with a strongly acidic OH group involved in a rather strong H-bond with the anion, and (ii) a typical strong Lewis acid, N[triple bond, length as m-dash]N-OH, with a positive charge localized to the central N atom and ionic interactions with the surrounding anions via the charged central N atom.
View Article and Find Full Text PDFComatose patients after cardiac arrest have a poor prognosis. Approximately half never awakes as a result of severe diffuse postanoxic encephalopathy. Several neuroprotective agents have been tested, however without significant effect.
View Article and Find Full Text PDFExtremely synchronized firing patterns such as those observed in brain diseases like epilepsy may result from excessive network excitability. Although network excitability is closely related to (excitatory) connectivity, a direct measure for network excitability remains unavailable. Several methods currently exist for estimating network connectivity, most of which are related to cross-correlation.
View Article and Find Full Text PDFBackground: While ghrelin was initially related to appetite stimulation and growth hormone secretion, it also has a neuroprotective effect in neurodegenerative diseases and regulates cognitive function. The cellular basis of those processes is related to synaptic efficacy and plasticity. Previous studies have shown that ghrelin not only stimulates synapse formation in cultured cortical neurons and hippocampal slices, but also alters some of the electrophysiological properties of neurons in the hypothalamus, amygdala and other subcortical areas.
View Article and Find Full Text PDFWhat is the strongest acid? Can a simple Brønsted acid be prepared that can protonate an alkane at room temperature? Can that acid be free of the complicating effects of added Lewis acids that are typical of common, difficult-to-handle superacid mixtures? The carborane superacid H(CHB11 F11 ) is that acid. It is an extremely moisture-sensitive solid, prepared by treatment of anhydrous HCl with [Et3 SiHSiEt3 ][CHB11 F11 ]. It adds H2 O to form [H3 O][CHB11 F11 ] and benzene to form the benzenium ion salt [C6 H7 ][CHB11 F11 ].
View Article and Find Full Text PDFArtificial nerve guidance channels enhance the regenerative effectiveness in an injured peripheral nerve but the existing design so far has been limited to basic straight tubes simply guiding the growth to bridge the gap. Hence, one of the goals in development of more effective neuroprostheses is to create bidirectional highly selective neuro-electronic interface between a prosthetic device and the severed nerve. A step towards improving selectivity for both recording and stimulation have been made with some recent in vitro studies which showed that three-dimensional (3D) bifurcating microchannels can separate neurites growing on a planar surface and bring them into contact with individual electrodes.
View Article and Find Full Text PDFGhrelin was initially related to appetite stimulation and growth hormone secretion. However, it also has a neuroprotective effect in neurodegenerative diseases and regulates cognitive function. The cellular basis of these processes is related to synaptic efficacy and plasticity.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
September 2012
Environmentally sensitive: A combination of C-H anion hydrogen bonding and hyperconjugative charge delocalization explains the sensitivity of the IR spectrum of the tert-butyl cation to its anion (see high-resolution X-ray structure with a CHB(11)Cl(11)(-) counterion). The νCH vibration of the cation scales linearly with the basicity of carborane anions on the νNH scale. The same also holds for the C(6)H(7)(+) benzenium ion.
View Article and Find Full Text PDFCell Mol Neurobiol
January 2012
Orexin A (OXA) is an excitatory hypothalamic neurotransmitter and ligand for Orexin Receptor-1 (OR1), isolated from a small group of hypothalamic neurons. OXA orchestrates different brain functions, and at the cognitive level some of the effects of insufficiency of OXA are well-known, for example in Parkinson's disease. It is widely assumed that deteriorated cognitive processes are related to impaired network connectivity.
View Article and Find Full Text PDFThe protonation of chloroethane by the strongest known solid superacid, the carborane acid H(CHB(11)Cl(11)), has been studied by quantitative IR spectroscopic methods to track mass balance and uncover previously unobserved chemistry. In the first step, an intermediate EtCl·H(CHB(11)Cl(11)) species without full proton transfer to EtCl can be observed when d(5)-deuterated chloroethane is used. It rapidly eliminates HCl (but not DCl) to form ethyl carborane, Et(CHB(11)Cl(11)), which binds a second molecule of chloroethane to form the Et(2)Cl(+) chloronium ion.
View Article and Find Full Text PDFThe 2-oxa-5-adamantyl carbocation 4 is shown to be a viable intermediate in several S(N)1 substitution reactions. However, attempts to observe the formation of 4 from various precursors by NMR methods (which succeed for the 1-adamantyl cation 5) failed, suggesting that 4 does not survive on longer timescales. DFT calculations suggest that the retro-Prins process (beta-cleavage, Grob fragmentation) to give enantiomeric (1R,5R)- and (1S,5S)-7-methylene-2-oxoniabicyclo[3.
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