Analysis of the Unusual Chemical Bonds and Dipole Moments of AeF- (Ae=Be-Ba): A Lesson in Covalent Bonding.

Quantum chemical calculations of the anions AeF- (Ae=Be-Ba) have been carried out using ab initio methods at the CCSD(T)/def2-TZVPP level and density functional theory employing BP86 with various basis sets. The detailed bonding analyses using different charge- and energy partitioning methods show that the molecules possess three distinctively different dative bonds in the lighter species with Ae=Be, Mg and four dative bonds when Ae=Ca, Sr, Ba. The occupied 2p atomic orbitals (AOs) and to a lesser degree the occupied 2s AO of F- donate electronic charge into the vacant spx(σ) and p(π) orbitals of Be and Mg which leads to a triple bond Ae F-. The heavier Ae atoms Ca, Sr, Ba use their vacant (n-1)d AOs as acceptor orbitals which enables them to form a second σ donor bond with F- that leads to quadruply bonded Ae F- (Ae=Ca-Ba). The presentation of molecular orbitals or charge distribution using only one isodensity value may give misleading information about the overall nature of the orbital or charge distribution. Better insights are given by contour line diagrams. The ELF calculations provide monosynaptic and disynaptic basins of AeF- which nicely agree with the analysis of the occupied molecular orbitals and with the charge density difference maps. A particular feature of the covalent bonds in AeF- concerns the inductive interaction of F- with the soft valence electrons in the (n)s valence orbitals of Ae. The polarization of the (n)s2 electrons induces a (n)spx hybridized lone-pair orbital at atom Ae, which yields a large dipole moment with the negative end at Ae. The concomitant formation of a vacant (n)spx AO of atom Ae, which overlaps with the occupied 2p(σ) AO of F-, leads to a strong covalent σ bond.

Case report: Hyponatremia is an initial presentation of Neuromyelitis optica spectrum disorder.

OBJECTIVE: Neuromyelitis optica spectrum disorders (NMOSD) is often misdiagnosed or delayed because of the complex and diverse clinical manifestations, especially the atypical initial presentation. Hyponatremia can be an infrequently isolated initial presentation of NMOSD and is associated with hypothalamus involvement. Awareness of this mechanism will help clinicians to identify NMOSD early, treat it in time and improve the prognosis. METHODS: We describe a 36-year-old woman who developed repeated hyponatremia and then experienced diplopia. Serum AQP4, MOG, MBP and GFAP antibody were detected, and NMOSD was finally diagnosed. RESULTS: She responded well to high-dose glucocorticoids. Sequential treatment with mycophenolate mofetil (MMF) was prescribed. Two-month follow-up revealed full recovery. So far, after 10 months, the patient still has no recurrence. CONCLUSION: For young patients, repeated hyponatremia, with or without slight fever, and no evidence of obvious infection, brain magnetic resonance imaging (MRI) and serum AQP4/MOG antibody detection may be useful to determine whether there is a possibility of NMOSD.

Diversification of the Carbodicarbene Class by Embedding an Anionic Component in its Scaffold.

Carbodicarbene (CDC) has become an emerging ligand in many fields due to its strong σ-donating ability.

Genuine quadruple bonds between two main-group atoms. Chemical bonding in AeF- (Ae = Be-Ba) and isoelectronic EF (E = B-Tl) and the particular role of d orbitals in covalent interactions of heavier alkaline-earth atoms.

Quantum chemical calculations of anions AeF- (Ae = Be-Ba) and isoelectronic group-13 molecules EF (E = B-Tl) have been carried out using ab initio methods at the CCSD(T)/def2-TZVPP level and density functional theory employing BP86 various basis sets. The equilibrium distances, bond dissociation energies and vibrational frequencies are reported. The alkali earth fluoride anions AeF- exhibit strong bonds between the closed-shell species Ae and F- with bond dissociation energies between 68.8 kcal mol-1 for MgF- and 87.5 kcal mol-1 for BeF- and they show an unusual increasing trend MgF- < CaF- < SrF- < BaF-. This is in contrast to the isoelectronic group-13 fluorides EF where the BDE continuously decreases from BF to TlF. The calculated dipole moments of AeF- are very large between 5.97 D for BeF- and 1.78 D for BaF- with the negative end always at the Ae atom (Ae→F-). This is explained by the location of the electronic charge of the lone pair at Ae, which is rather distant from the nucleus. The analysis of the electronic structure of AeF- suggests significant charge donation Ae←F- into the vacant valence orbitals of Ae. A bonding analysis with the EDA-NOCV method suggests that the molecules are mainly covalently bonded. The strongest orbital interaction in the anions comes from the inductive polarization of the 2pσ electrons of F-, which leads to a hybridization of the (n)s and (n)pσ AOs at Ae. There are two degenerate π donor interactions Ae←F- in all anions AeF-, which provide 25-30% to the covalent bonding. There is another σ orbital interaction in the anions, which is very weak in BeF- and MgF-. In contrast, the second stabilizing σ orbital interaction in CaF-, SrF- and BaF- yields a strongly stabilizing σ orbital, because the Ae atoms use their (n - 1)dσ AOs for bonding. The energy lowering of the second σ interaction in the latter anions is even stronger than the π bonding. The EDA-NOCV results suggest that BeF- and MgF- have three strongly polarized bonds, whereas CaF-, SrF- and BaF- have four bonding orbitals. The quadruple bonds in the heavier alkaline earth species are made possible because they use s/d valence orbitals like transition metals for covalent bonding. The EDA-NOCV analysis of the group-13 fluorides EF gives a conventional picture with one very strong σ bond and two rather weak π interactions.

Discovery and synthesis of cyclohexenyl derivatives as modulators of CC chemokine receptor 2 activity.

A novel cyclohexenyl series of CCR2 antagonists has been discovered. This series of small, rigid compounds exhibits submicromolar binding affinity for CCR2. Modification of the substituents on the cyclohexene ring led to the identification of potent CCR2 antagonists. Progress from initial lead 5 (IC50=700nM) to (-)-38 (IC50=9.0nM) is discussed.

Characterization of the interactions between ß-amyloid peptide and the membranes of human SK-N-SH cells.

Interaction of ß-amyloid peptide (Aß) with cell membranes is thought to be an initial step in Alzheimer's disease (AD). However, some data are controversial and the underlying mechanisms remain unclear. In this report, two populations of Aß were found in human SK-N-SH neuroblastoma cells. Notably, one of the Aß populations was tightly inserted into the plasma membrane whilst the other was only peripherally associated with it. Here we show that reducing membrane cholesterol decreased the number of membrane-embedded Aßs and increased the number of membrane-attached Aßs. We also found that cholesterol depletion inhibited Aß degradation and exacerbated Aß-mediated cytotoxicity. Our detailed and direct observations provide specific insights into the mechanism of Aß membrane-associated toxicity.

Crystal structure of N'-(2,6-di-methyl-phen-yl)benzene-carboximidamide tetra-hydro-furan monosolvate.

The asymmetric unit of the title compound, C15H16N2·C4H8O, contains two amidine mol-ecules (A and B) with slightly different conformations and two tetra-hydro-furan (THF) solvent mol-ecules. In the amidine mol-ecules, the di-methyl-phenyl ring and the NH2 group lie to the same side of the N=C bond and the dihedral angles between the aromatic rings are 54.25 (7) (mol-ecule A) and 58.88 (6) ° (mol-ecule B). In the crystal, N-H⋯N hydrogen bonds link the amidine mol-ecules into [100] C(4) chains of alternating A and B mol-ecules. Both amidine mol-ecules form an N-H⋯O hydrogen bond to an adjacent THF solvent mol-ecule.

A lifespan observation of a novel mouse model: in vivo evidence supports aß oligomer hypothesis.

Transgenic mouse models are powerful tools in exploring the mechanisms of AD. Most current transgenic models of AD mimic the memory impairment and the main pathologic features, among which the formation of beta-amyloid (Aß) plaques is considered a dominant pathologic event. Recently, Aß oligomers have been identified as more neurotoxic than Aß plaques. However, no ideal transgenic mouse model directly support Aß oligomers as a neurotoxic species due to the puzzling effects of amyloid plaques in the more widely-used models. Here, we constructed a single-mutant transgenic (Tg) model harboring the PS1V97L mutation and used Non-Tg littermates as a control group. Employing the Morris water maze, electrophysiology, immunohistochemistry, biochemistry, and electron microscopy, we investigated behavioral changes and pathology progression in our single-mutant transgenic model. We discovered the pathological alteration of intraneuronal accumulation of Aß oligomers without Aß plaques in the PS1V97L-Tg mouse model, which might be the result of PS1 gene mutation. Following Aß oligomers, we detected synaptic alteration, tau hyperphosphorylation and glial activation. This model supports an initial role for Aß oligomers in the onset of AD and suggests that Aß plaques may not be the only prerequisite. This model provides a useful tool for studying the role of Aß oligomers in AD pathogenesis.

Decreased serum levels of the angiogenic factors VEGF and TGF-ß1 in Alzheimer's disease and amnestic mild cognitive impairment.

Growing evidence suggests that angiogenesis might represent a new pathogenic mechanism involved in the progression of Alzheimer's disease (AD). Vascular endothelial growth factor (VEGF) and transforming growth factor-ß1 (TGF-ß1) are two cytokines having a pivotal role in angiogenesis. In the present study, serum VEGF and TGF-ß1 levels were measured with ELISA in 31 AD patients, 28 amnestic mild cognitive impairment (aMCI) patients and 29 controls. VEGF concentration in serum of AD patients was significantly lower than that in aMCI patients and controls (p<0.05). Serum VEGF levels in aMCI patients were also significantly decreased compared to controls (p<0.05). Serum TGF-ß1 levels in AD patients were significantly lower than those in controls (p<0.05). There was a negative correlation between serum VEGF/TGF-ß1 levels and the Clinical Dementia Rating (CDR) scores (p<0.05) and a positive correlation between serum VEGF levels and TGF-ß1 levels (p<0.05). These observations suggest that angiogenesis might be involved in the onset process of AD and the decrease of angiogenic factors might be related to the severity of cognitive impairment.

N-Cyclo-hexyl-3-methyl-benzamidine.

The title amidine compound, C14H20N2, prepared by a one-pot reaction, is asymmetric as only one N atom has an alkyl substituent. The terminal cyclo-hexyl group connected to the amino N atom is located on the other side of the N-C-N skeleton to the 4-methylbenzene ring and has a chair conformation. The dihedral angle between the phenyl ring and the NCN plane is 47.87 (12)°. In the crystal, mol-ecules are linked via N-H⋯N hydrogen bonds, forming chains propagating along the a-axis direction.

Discovery and lead optimization of a novel series of CC chemokine receptor 1 (CCR1)-selective piperidine antagonists via parallel synthesis.

A series of novel, potent CCR1 inhibitors was developed from a moderately active hit using an iterative parallel synthesis approach. The initial hit (composed of three subunits: an amine, a central amino acid, and an N-terminal cap) became the basis for a series of parallel chemical libraries designed to generate SAR data. Libraries were synthesized that explored each of the three subunits; the CCR1 binding data obtained revealed the following: (1) changes to the amine are not well tolerated; (2) small alkylamino acids are preferred in the center of the molecule; (3) substitutions at the N-terminus are generally well tolerated. These data were used to drive the optimization of the series, ultimately providing a lead with a CCR1 binding IC(50) of 28 nM (48). This lead demonstrates high selectivity for CCR1 over other CCR-family members, high microsomal stability, and good pharmacokinetics in mice.

Membrane localization of beta-amyloid 1-42 in lysosomes: a possible mechanism for lysosome labilization.

beta-Amyloid peptide (Abeta42) is the core protein of amyloid plaque in Alzheimer disease. The intracellular accumulation of Abeta42 in the endosomal/lysosomal system has been under investigation for many years, but the direct link between Abeta42 accumulation and dysfunction of the endosomal/lysosomal system is still largely unknown. Here, we found that both in vitro and in vivo, a major portion of Abeta42 was tightly inserted into and a small portion peripherally associated with the lysosomal membrane, whereas its soluble portion was minimal. We also found that the Abeta42 molecules inserted into the membrane tended to form multiple oligomeric aggregates, whereas Abeta40 peptides formed only dimers. Neutralizing lysosomal pH in differentiated PC12 cells decreased the lysosomal membrane insertion of Abeta42 and moderated Abeta42-induced lysosomal labilization and cytotoxicity. Our findings, thus, suggest that the membrane-inserted portion of Abeta42 accumulated in lysosomes may destabilize the lysosomal membrane and induce neurotoxicity.

Cellular internalization of exosomes occurs through phagocytosis.

Exosomes play important roles in many physiological and pathological processes. However, the exosome-cell interaction mode and the intracellular trafficking pathway of exosomes in their recipient cells remain unclear. Here, we report that exosomes derived from K562 or MT4 cells are internalized more efficiently by phagocytes than by non-phagocytic cells. Most exosomes were observed attached to the plasma membrane of non-phagocytic cells, while in phagocytic cells these exosomes were found to enter via phagocytosis. Specifically, they moved to phagosomes together with phagocytic polystyrene carboxylate-modified latex beads (biospheres) and were further sorted into phagolysosomes. Moreover, exosome internalization was dependent on the actin cytoskeleton and phosphatidylinositol 3-kinase, and could be inhibited by the knockdown of dynamin2 or overexpression of a dominant-negative form of dynamin2. Further, antibody pretreatment assays demonstrated that tim4 but not tim1 was involved in exosomes uptake. We also found that exosomes did not enter the internalization pathway involving caveolae, macropinocytosis and clathrin-coated vesicles. Our observation that the cellular uptake of exosomes occurs through phagocytosis has important implications for exosome-cell interactions and the exosome intracellular trafficking pathway.

Potent, exceptionally selective, orally bioavailable inhibitors of TNF-alpha Converting Enzyme (TACE): novel 2-substituted-1H-benzo[d]imidazol-1-yl)methyl)benzamide P1' substituents.

Novel ((2-substituted-1H-benzo[d]imidazol-1-yl)methyl)benzamides were found to be excellent P1' substituents in conjunction with unique constrained beta-amino hydroxamic acid scaffolds for the discovery of potent selective inhibitors of TNF-alpha Converting Enzyme (TACE). Optimized examples proved potent for TACE, exceptionally selective over a wide panel of MMP and ADAM proteases, potent in the suppression of LPS-induced TNF-alpha in human whole blood and orally bioavailable.

Alpha,Beta-cyclic-beta-benzamido hydroxamic acids: Novel oxaspiro[4.4]nonane templates for the discovery of potent, selective, orally bioavailable inhibitors of tumor necrosis factor-alpha converting enzyme (TACE).

Two novel oxaspiro[4.4]nonane beta-benzamido hydroxamic scaffolds have been synthesized in enantio- and diasteriomerically pure form. These templates proved to be exceptional platforms that have led to the discovery of potent inhibitors of TACE that are active in a cellular assay measuring suppression of LPS-induced TNF-alpha. Furthermore, these inhibitors are selective against related MMPs, demonstrate permeability in a Caco-2 assay, and display good oral bioavailability.

Potent, selective, orally bioavailable inhibitors of tumor necrosis factor-alpha converting enzyme (TACE): discovery of indole, benzofuran, imidazopyridine and pyrazolopyridine P1' substituents.

Potent and selective inhibitors of tumor necrosis factor-alpha converting enzyme (TACE) were discovered with several new heterocyclic P1' groups in conjunction with cyclic beta-amino hydroxamic acid scaffolds. Among them, the pyrazolopyridine provided the best overall profile when combined with tetrahydropyran beta-amino hydroxamic acid scaffold. Specifically, inhibitor 49 showed IC(50) value of 1 nM against porcine TACE and 170 nM in the suppression of LPS-induced TNF-alpha of human whole blood. Compound 49 also displayed excellent selectivity over a wide panel of MMPs as well as excellent oral bioavailability (F%>90%) in rat n-in-1 PK studies.

Alpha,beta-cyclic-beta-benzamido hydroxamic acids: novel templates for the design, synthesis, and evaluation of selective inhibitors of TNF-alpha converting enzyme (TACE).

Selective inhibitors of TNF-alpha Converting Enzyme (TACE) based on (1R,2S)-cyclopentyl, (3S,4S)-pyrrolidinyl, and (3R,4S)-tetrahydrofuranyl beta-benzamido hydroxamic acids have been synthesized and evaluated. This study has led to the discovery of novel inhibitors whose profiles include activity against TACE in an enzyme assay, potency in the suppression of LPS-stimulated TNF-alpha in human whole blood, selectivity against a panel of MMPs and oral bioavailability.

Discovery of beta-benzamido hydroxamic acids as potent, selective, and orally bioavailable TACE inhibitors.

Beta-benzamido hydroxamic acids were discovered as potent TACE inhibitors. A computer model was constructed to help understanding the binding activities and guiding SAR study. SAR optimization led to the discovery of compound 30 which met all in vitro and in vivo criteria for the program and was selected for further evaluation.

Pharmacokinetics and pharmacodynamics of DPC 333 ((2R)-2-((3R)-3-amino-3{4-[2-methyl-4-quinolinyl) methoxy] phenyl}-2-oxopyrrolidinyl)-N-hydroxy-4-methylpentanamide)), a potent and selective inhibitor of tumor necrosis factor alpha-converting enzyme in rodents, dogs, chimpanzees, and humans.

DPC 333 ((2R)-2-((3R)-3-amino-3{4-[2-methyl-4-quinolinyl) methoxy] phenyl}-2-oxopyrrolidinyl)-N-hydroxy-4-methylpentanamide)) is a potent and selective inhibitor of tumor necrosis factor (TNF)-alpha-converting enzyme (TACE). It significantly inhibits lipopolysaccharide-induced soluble TNF-alpha production in blood from rodents, chimpanzee, and human, with IC(50) values ranging from 17 to 100 nM. In rodent models of endotoxemia, DPC 333 inhibited the production of TNF-alpha in a dose-dependent manner, with an oral ED(50) ranging from 1.1 to 6.1 mg/kg. Oral dosing of DPC 333 at 5.5 mg/kg daily for 2 weeks in a rat collagen antibody-induced arthritis model suppressed the maximal response by approximately 50%. DPC 333 was distributed widely to tissues including the synovium, the site of action for antiarthritic drugs. Pharmacokinetic and pharmacodynamic studies in chimpanzee revealed a systemic clearance of 0.4 l/h/kg, a V(ss) of 0.6 l/kg, an oral bioavailability of 17%, and an ex vivo IC(50) for the suppression of TNF-alpha production of 55 nM (n = 1). In a phase I clinical trial with male volunteers after single escalating doses of oral DPC 333, the terminal half-life was between 3 and 6 h and the ex vivo IC(50) for suppressing TNF-alpha production was 113 nM. Measurement of the suppression of TNF-alpha production ex vivo may serve as a good biomarker in evaluating the therapeutic efficacy of TACE inhibitors. Overall, the pharmacological profiles of DPC 333 support the notion that suppression of TNF-alpha with TACE inhibitors like DPC 333 may provide a novel approach in the treatment of various inflammatory diseases including rheumatoid arthritis, via control of excessive TNF-alpha production.

Synthesis and structure-activity relationship of a novel, non-hydroxamate series of TNF-alpha converting enzyme inhibitors.

A novel series of TNF-alpha converting enzyme (TACE) inhibitors which are non-hydroxamate have been discovered. These compounds use a triazolethione moiety as the zinc binding ligand and exhibit IC50 values from 1.5 to 100 nM in a porcine TACE assay. They also have excellent selectivities over other MMPs.