Nature of beryllium, magnesium, and zinc bonds in carbene ⋯MX2⋯MX_2 (M = Be, Mg, Zn; X = H, Br) dimers revealed by the IQA, ETS-NOCV and LED methods

The nature of beryllium–, magnesium– and zinc–carbene bonds in the cyclopropenylidene⋯MX [Formula: see text] (M = Be, Mg, Zn; X = H, Br) and imidazol-2-ylidene⋯MBr [Formula: see text] dimers is investigated by the joint use of the topological QTAIM-based IQA decomposition scheme, the molecular orbital-based ETS-NOCV charge and energy decomposition method, and the LED energy decomposition approach based on the state-of-the-art DLPNO-CCSD(T) method. All these methods show that the C⋯M bond strengthens according to the following order: Zn < Mg [Formula: see text] Be. Electrostatics is proved to be the dominant bond component, whereas the orbital component is far less important. It is shown that QTAIM/IQA underestimates electrostatic contribution for zinc bonds with respect to both ETS-NOCV and LED schemes. The [Formula: see text] carbene→MX [Formula: see text] donation appears to be much more important than the MX [Formula: see text] carbene back-donation of [Formula: see text] symmetry. The substitution of hydrogen atoms by bromine (X in MX [Formula: see text]) strengthens the metal–carbene bond in all cases. The physical origin of rotational barriers has been unveiled by the ETS-NOCV approach

Denture-related stomatitis is associated with endothelial dysfunction

Oral inflammation, such as periodontitis, can lead to endothelial dysfunction, accelerated atherosclerosis, and vascular dysfunction. The relationship between vascular dysfunction and other common forms of oral infections such as denture-related stomatitis (DRS) is unknown. Similar risk factors predispose to both conditions including smoking, diabetes, age, and obesity. Accordingly, we aimed to investigate endothelial function and major vascular disease risk factors in 44 consecutive patients with dentures with clinical and microbiological features of DRS (n = 20) and without DRS (n = 24). While there was a tendency for higher occurrence of diabetes and smoking, groups did not differ significantly in respect to major vascular disease risk factors. Groups did not differ in main ambulatory blood pressure, total cholesterol, or even CRP. Importantly, flow mediated dilatation (FMD) was significantly lower in DRS than in non-DRS subjects, while nitroglycerin induced vasorelaxation (NMD) or intima-media thickness (IMT) was similar. Interestingly, while triglyceride levels were normal in both groups, they were higher in DRS subjects, although they did not correlate with either FMD or NMD. Conclusions. Denture related stomatitis is associated with endothelial dysfunction in elderly patients with dentures. This is in part related to the fact that diabetes and smoking increase risk of both DRS and cardiovascular disease

Mechanisms of oxidative stress in human aortic aneurysms — association with clinical risk factors for atherosclerosis and disease severity

Aortic abdominal aneurysms (AAA) are important causes of cardiovascular morbidity and mortality. Oxidative stress may link multiple mechanisms of AAA including vascular inflammation and increased metalloproteinase activity. However, the mechanisms of vascular free radical production remain unknown. Accordingly, we aimed to determine sources and molecular regulation of vascular superoxide (O2radical dot−) production in human AAA. Methods and results: AAA segments and matched non-dilated aortic samples were obtained from 40 subjects undergoing AAA repair. MDA levels (determined by HPLC/MS) were greater in plasma of AAA subjects (n = 16) than in risk factor matched controls (n = 16). Similarly, superoxide production, measured by lucigenin chemiluminescence and dihydroethidium fluorescence, was increased in aneurysmatic segments compared to non-dilated aortic specimens. NADPH oxidases and iNOS are the primary sources of O2radical dot− in AAA. Xanthine oxidase, mitochondrial oxidases and cyclooxygenase inhibition had minor or no effect. Protein kinase C inhibition had no effect on superoxide production in AAA. NADPH oxidase subunit mRNA levels for p22phox, nox2 and nox5 were significantly increased in AAAs while nox4 mRNA expression was lower. Superoxide production was higher in subjects with increased AAA repair risk Vanzetto score and was significantly associated with smoking, hypercholesterolemia and presence of CAD in AAA cohort. Basal superoxide production and NADPH oxidase activity were correlated to aneurysm size. Conclusions: Increased expression and activity of NADPH oxidases are important mechanisms underlying oxidative stress in human aortic abdominal aneurysm. Uncoupled iNOS may link oxidative stress to inflammation in AAA. Oxidative stress is related to aneurysm size and major clinical risk factors in AAA patients

T cells are dominant population in human abdominal aortic aneurysms and their infiltration in the perivascular tissue correlates with disease severity

Abdominal Aortic Aneurysm (AAA) is a major cause of cardiovascular mortality. Adverse changes in vascular phenotype act in concert with chronic inflammation to promote AAA progression. Perivascular adipose tissue (PVAT) helps maintain vascular homeostasis but when inflamed and dysfunctional, can also promote vascular pathology. Previous studies suggested that PVAT may be an important site of vascular inflammation in AAA; however, a detailed assessment of leukocyte populations in human AAA, their anatomic location in the vessel wall and correlation to AAA size remain undefined. Accordingly, we performed in depth immunophenotyping of cells infiltrating the pathologically altered perivascular tissue (PVT) and vessel wall in AAA samples at the site of maximal dilatation (n=51 patients). Flow cytometry revealed that T cells, rather than macrophages, are the major leukocyte subset in AAA and that their greatest accumulations occur in PVT. Both CD4+ and CD8+ T cell populations are highly activated in both compartments, with CD4+ T cells displaying the highest activation status within the AAA wall. Finally, we observed a positive relationship between T cell infiltration in PVT and AAA wall. Interestingly, only PVT T cell infiltration was strongly related to tertiles of AAA size. In summary, this study highlights an important role for PVT as a reservoir of T lymphocytes and potentially as a key site in modulating the underlying inflammation in AAA

Theoretical description of isoelectronic, inorganic (BN), and mixed (BN/CC) butane analogues.

Modyfikacje układów organicznych podukładami borowo-azotowymi w celu zmiany niektórych ich właściwości, takich jak reaktywność, stabilność, czy przewodnictwo, stają się coraz bardziej popularne przy badaniu nowych materiałów. Jest to możliwe, gdyż para atomów bor-azot jest izoelektronowa w stosunku do pary węgiel-węgiel, a suma ich promieni walencyjnych jest bardzo zbliżona do podwojonego promienia walencyjnego atomu węgla.Celem niniejszej pracy jest teoretyczna charakterystyka grupy związków będących izoelektronowymi, organiczno-nieorganicznymi analogami butanu, w których pary atomów węgla systematycznie zastępowano parami atomów boru i azotu. Pod uwagę wzięto związki: BH3NH2BH2NH3, BH3CH2CH2NH3, CH3BH2NH2CH3, BH3CH2NH2CH3, NH3CH2BH2CH3 i NH3BH2CH2CH3. Przy użyciu metody DFT (BLYP/TZ2P) wspomaganej podejściami QTAIM oraz ETS-NOCV, opisano stabilności, geometrię i strukturę elektronową cząsteczek oraz obecne w nich oddziaływania wewnątrzcząsteczkowe. Wyróżniono grupę związków podobnych do butanu pod względem geometrii (CH3BH2NH2CH3, BH3CH2NH2CH3, NH3CH2BH2CH3 i NH3BH2CH2CH3), oraz drugą, znacznie się od niego różniącą (BH3NH2BH2NH3, BH3CH2CH2NH3). Związki należące do drugiej grupy, w odróżnieniu od butanu, są stabilne w konformacji gauche, w czym dużą rolę odgrywają występujące w nich oddziaływanie dwuwodorowe (B-H•••H-N). Uzyskane wyniki obliczeń wskazują na stabilność termodynamiczną badanych pochodnych organiczno-nieorganicznych, co sugeruje, że mogą zostać one uzyskane na drodze eksperymentalnej. Zaproponowano schemat syntezy jednej z pochodnych (NH3BH2CH2CH3).Boron and nitrogen based modifications of organic compounds are becoming more and more popular in new material science. They are known to be able to change a range of properties, such as reactivity, stability and conductivity, without dramatically altering the structure. Modifications like these are possible because of the isoelectronic nature of the boron-nitrogen pair in comparison to carbon-carbon pair, as well as similarity between the sum of the valence radii of the boron-nitrogen pair to carbon-carbon pair. The main goal of the thesis is theoretical description of the group of isoelectronic, organic-inorganic compounds based on butane, composed of boron and nitrogen atoms. Systematical replacement of two carbon atoms by boron and nitrogen were considered; BH3NH2BH2NH3, BH3CH2CH2NH3, CH3BH2NH2CH3, BH3CH2NH2CH3, NH3CH2BH2CH3 and NH3BH2CH2CH3 were taken into account. Geometries, their stability, the electronic structure and intramolecular interactions have been studied with the use of DFT method (BLYP/TZ2P), supported by QTAIM and ETS-NOCV calculations. The two groups of compounds can be distinguished: those that are very similar to fully organic butane in the terms of geometry (CH3BH2NH2CH3, BH3CH2NH2CH3, NH3CH2BH2CH3 and NH3BH2CH2CH3), and those that are very different. The compounds belonging to the second group (BH3NH2BH2NH3, BH3CH2CH2NH3) are more stable in the gauche conformation, unlike butane which prefers the trans conformation. Dihydrogen interactions (B-H•••H-N) between the hydrogen atoms in terminal BH3 and NH3 groups play major role in this phenomenon. The obtained data suggests that the molecules under study are thermodynamically stable, and thus, are viable experimentally. Synthesis scheme of the one of compounds (NH3BH2CH2CH3) has been proposed

Kinetic and potential energy contributions to a chemical bond from the charge and energy decomposition scheme of extended transition state natural orbitals for chemical valence

This work provides novel physical insight into the nature of a chemical bond by exploring qualitative and quantitative relations between the natural orbitals for chemical valence (NOCV)-based deformation density bonding channels Δρ<i>_i</i> (<i>i</i> = σ, π, δ, etc.) and the corresponding kinetic Δ<i>T_i</i> and potential energy Δ<i>V_i</i> contributions within the charge and energy decomposition scheme ETS-NOCV implemented in the Kohn–Sham-based Amsterdam Density Functional (ADF) package. It is determined that interfragment dative and covalent-type electron charge reorganizations upon formation of a series of strong and weak bonds employing main-group elements are due to lowering of the negative kinetic energy contributions, as opposed to the intrafragment polarizations (e.g., hyperconjugations in ethane), which are, in contrary, driven by the potential energy (electrostatic) component. Complementary, formation of π-contributions in N₂ is accompanied by lowering of both kinetic and potential energy constituents. Remarkably, well-known globally stabilizing back-donation (M → ligand, where M is a transition metal) and donation (ligand → M) processes, ubiquitous in organometallic species, have been discovered for the first time to be driven by the opposite Δ<i>T_i</i>/Δ<i>V_i</i> mechanisms, namely, the former contribution is associated with the negative kinetic term (which outweighs the positive potential energy), whereas the latter charge delocalization into electrophilic transition metals leads to an attractive electrostatic stabilization (and positive kinetic energy)

Origin of remarkably different acidity of hydroxycoumarins : joint experimental and theoretical studies

In the present work the origin of highly varied acidity of hydroxycoumarins (p<i>K</i>_a values) has been for the first time investigated by joint experimental and computational studies. The structurally simple regio-isomers differing in the location of hydroxyl group, 3-hydroxycoumarin (3-HC), 4-hydroxycoumarin (4-HC), 6-hydroxycoumarin (6-HC), 7-hydroxycoumarin (7-HC), as well as 4,7-dihydroxycoumarin (4,7-HC) and the larger 4-hydroxycoumarin-based derivatives: warfarin (WAR), 7-hydroxywarfarin (W7), coumatetralyl (CT), and 10-hydroxywarfarin (W10), have been compared in terms of enthalpy–entropy relationships accounting for the observed p<i>K</i>_a values. We have revealed that in the case of large molecules the acidic proton is stabilized by the following noncovalent interactions OH···O (WAR and W7), OH···π (CT), and OH···OH···O (W10), this effect leads to a compensatory enthalpy–entropy relation and yields a moderate p<i>K</i>_a increase. On the other hand, different location of the hydroxyl group in the regio-isomers (3-HC, 4-HC, 6-HC, and 7-HC) leads to the massive changes in acidity due to a lack of enthalpy–entropy compensation. Our results suggest that the solvent–solute interactions and electron delocalization degree in anions contribute to the observed behaviors. Such knowledge can be useful in the future to design novel systems exhibiting desired acid–base properties, and to elucidate enthalpy–entropy compensation phenomena

Non-Covalent Interactions in Hydrogen Storage Materials LiN(CH3)2BH3 and KN(CH3)2BH3

In the present work, an in-depth, qualitative and quantitative description of non-covalent interactions in the hydrogen storage materials LiN(CH3)2BH3 and KN(CH3)2BH3 was performed by means of the charge and energy decomposition method (ETS-NOCV) as well as the Interacting Quantum Atoms (IQA) approach. It was determined that both crystals are stabilized by electrostatically dominated intra- and intermolecular M∙∙∙H–B interactions (M = Li, K). For LiN(CH3)2BH3 the intramolecular charge transfer appeared (B–H→Li) to be more pronounced compared with the corresponding intermolecular contribution. We clarified for the first time, based on the ETS-NOCV and IQA methods, that homopolar BH∙∙∙HB interactions in LiN(CH3)2BH3 can be considered as destabilizing (due to the dominance of repulsion caused by negatively charged borane units), despite the fact that some charge delocalization within BH∙∙∙HB contacts is enforced (which explains H∙∙∙H bond critical points found from the QTAIM method). Interestingly, quite similar (to BH∙∙∙HB) intermolecular homopolar dihydrogen bonds CH∙∙∙HC appared to significantly stabilize both crystals—the ETS-NOCV scheme allowed us to conclude that CH∙∙∙HC interactions are dispersion dominated, however, the electrostatic and σ/σ*(C–H) charge transfer contributions are also important. These interactions appeared to be more pronounced in KN(CH3)2BH3 compared with LiN(CH3)2BH3