Molecular Model with Quantum Mechanical Bonding Information Bohórquez, Hugo J; Boyd, Russell J; Matta, Chérif F
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
11/2011, Letnik:
115, Številka:
45
Journal Article
Recenzirano
The molecular structure can be defined quantum mechanically thanks to the theory of atoms in molecules. Here, we report a new molecular model that reflects quantum mechanical properties of the ...chemical bonds. This graphical representation of molecules is based on the topology of the electron density at the critical points. The eigenvalues of the Hessian are used for depicting the critical points three-dimensionally. The bond path linking two atoms has a thickness that is proportional to the electron density at the bond critical point. The nuclei are represented according to the experimentally determined atomic radii. The resulting molecular structures are similar to the traditional ball and stick ones, with the difference that in this model each object included in the plot provides topological information about the atoms and bonding interactions. As a result, the character and intensity of any given interatomic interaction can be identified by visual inspection, including the noncovalent ones. Because similar bonding interactions have similar plots, this tool permits the visualization of chemical bond transferability, revealing the presence of functional groups in large molecules.
•Unregulated inflammation in autistic patients in the absence of insult or injury.•Microglia and astrocytes play physiological roles in synapse maintenance.•Altered glial function could contribute to ...neural deficits.•Emerging evidence for a role for the Gut-Brain Axis in ASD.•Glial-driven disruptions in neural connectivity may contribute to core behavioural traits in autism.
Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterised by deficits in social communication and restricted or repetitive behaviours. The clinical presentation of ASD is highly variable and diagnosis is based on the presence of impaired social communication and repetitive and/or restricted behaviours. Although the precise pathophysiologies underlying ASD are unclear, growing evidence supports a role for dysregulated neuroinflammation. The potential involvement of microglia and astrocytes reactive to inflammatory stimuli in ASD has generated much interest due to their varied roles including in mounting an immune response and regulating synaptic function. Increased numbers of reactive microglial and astrocytes in both ASD postmortem tissue and animal models have been reported. Whether dysregulation of glial subtypes exacerbates alterations in neural connectivity in the brain of autistic patients is not well explored. A role for the gut-brain axis involving microbial-immune-neuronal cross talk is also a growing area of neuroinflammation research. Greater understanding of these interactions under patho/physiological conditions and the identification of consistent immune profile abnormalities can potentially lead to more reliable diagnostic measures and treatments in ASD.
Bio scaffolds used for cutaneous tissue regeneration is a challenging issue in the healthcare system. To help this problem, we aimed to report on fabrication and characterization of citric acid ...cross-linked carboxymethyl guar gum (CMGG) nanocomposite films loaded with ciprofloxacin for faster wound healing application. Differential scanning calorimeter (DSC) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy studies, dynamic light scattering (DLS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used as analytical techniques for characterization of the nanocomposite film. The morphological characters of nanocomposite film were determined by SEM. The prepared scaffolds were evaluated for the carboxyl content and swelling ratio. Ciprofloxacin was loaded into scaffold and drug release was studied at pH 7.4. The hemolysis assay was used to study the biocompatibility of scaffold films. The formation of ester cross-links between citric acid and CMGG was confirmed by DSC and ATR- FTIR. The total carboxyl content of scaffold was found to be decreased when the amount of CMGG was increased. The swelling of scaffold film was found to be decreased with increase in curing temperature and time. CMGG scaffold films showed high drug loading with non-Fickian release mechanism suggesting controlled release of drug. In vivo wound healing studies were carried out for 5 days. In this study we observed a faster wound healing effect within 5 days by incorporation of ciprofloxacin in the CMGG film and found biocompatible. Hence, these Nanocomposite films show greater potential in treating wounds.
Abstract The classic view assumes banks prioritize immediate repayment by selling assets until default. We endogenize run frequency and study how general settlement rules trade off liquidity ...provision net of fire sale losses against induced run incentives. Panic runs are eliminated when all illiquid assets are sold under orderly resolution, but liquidity provision in a run is minimal. When suspension after some fire sales is followed by immediate liquidation, run frequency falls then rises in suspension delay. Thus, optimal suspension may require some sale of illiquid assets, in contrast to MMF norms. Ex post discretion induces excessive liquidation and more frequent runs. (JEL D8, G21)
Several plant species such as Pfaffia glomerata are widely used in traditional Brazilian medicine as stimulants and aphrodisiacs. In this regard, the aim of our study was to explore the effects of ...the long‐term intake of the hydro‐alcoholic root extract of P glomerata on the germ and somatic cells within the seminiferous tubules in adult Balb/c mice. The experimental groups were placed as: controls (water and DMSO), and treated with 300 and 400 mg/kg of the root extract. The number of germ and somatic cells, the proportion of pathological seminiferous tubules, and the germ cell apoptotic levels were evaluated. The volume and proportion of the seminiferous epithelium was decreased after the extract intake due to the increased germ cell apoptotic levels. Vacuolization of Sertoli cell cytoplasm was observed widely in pathological tubules, along with fully disorganized epithelia, showing multinucleated cells, which lead to decreased daily sperm production. Taken together, our results indicate that long‐term intake of the P glomerata caused deleterious effects on spermatogenesis by inducing apoptosis and altering the seminiferous tubule's epithelial dynamics.
Crystallography and quantum mechanics have always been tightly connected because reliable quantum mechanical models are needed to determine crystal structures. Due to this natural synergy, nowadays ...accurate distributions of electrons in space can be obtained from diffraction and scattering experiments. In the original definition of quantum crystallography (QCr) given by Massa, Karle and Huang, direct extraction of wavefunctions or density matrices from measured intensities of reflections or, conversely, ad hoc quantum mechanical calculations to enhance the accuracy of the crystallographic refinement are implicated. Nevertheless, many other active and emerging research areas involving quantum mechanics and scattering experiments are not covered by the original definition although they enable to observe and explain quantum phenomena as accurately and successfully as the original strategies. Therefore, we give an overview over current research that is related to a broader notion of QCr, and discuss options how QCr can evolve to become a complete and independent domain of natural sciences. The goal of this paper is to initiate discussions around QCr, but not to find a final definition of the field.
Between Two Worlds—A New World: An amalgamation of quantum mechanics and diffraction experiments is a magnifying lens for the quantum phenomena in molecules and materials. In this Review, the new research domain “quantum crystallography” is debated in the context of current research fields. The perspective of becoming an independent natural science is outlined.
Bader’s quantum theory of atoms in molecules (QTAIM) and chemical graph theory, merged in the localization–delocalization matrices (LDMs) and the electron-density-weighted connectivity matrices ...(EDWCM), are shown to benefit in computational speed from the kernel energy method (KEM). The LDM and EDWCM quantum chemical graph matrices of a 66-atom C46H20 hydrogen-terminated armchair graphene nanoribbon, in 14 (2×7) rings of C 2v symmetry, are accurately reconstructed from kernel fragments. (This includes the full sets of electron densities at 84 bond critical points and 19 ring critical points, and the full sets of 66 localization and 4290 delocalization indices (LIs and DIs).) The average absolute deviations between KEM and directly calculated atomic electron populations, obtained from the sum of the LIs and half of the DIs of an atom, are 0.0012 ± 0.0018 e – (∼0.02 ± 0.03%) for carbon atoms and 0.0007 ± 0.0003 e – (∼0.01 ± 0.01%) for hydrogen atoms. The integration errors in the total electron population (296 electrons) are +0.0003 e – for the direct calculation (+0.0001%) and +0.0022 e – for KEM (+0.0007%). The accuracy of the KEM matrix elements is, thus, probably of the order of magnitude of the combined precision of the electronic structure calculation and the atomic integrations. KEM appears capable of delivering not only the total energies with chemical accuracy (which is well documented) but also local and nonlocal properties accurately, including the DIs between the fragments (crossing fragmentation lines). Matrices of the intact ribbon, the kernels, the KEM-reconstructed ribbon, and errors are available as Supporting Information.
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