New Trimethoxybenzamides and Trimethoxyphenylureas Derived from Dimethylcarbazole as Cytotoxic Agents. Part I

A convenient synthesis of novel functionalized 1,4‐dimethylcarbazole derivatives containing 3,4,5‐trimethoxybenzamido‐ureido or N‐(3,4,5‐trimethoxyphenyl)ureido group starting from their corresponding indole derivatives is reported. Three derivatives prepared ( 5g , 6c , and 6g ) were active against leukemia cell lines HL60. Both 5g and 6g showed potent antiproliferative activity against KB cell lines, likely associated with the inhibition of tubulin polymerization.     

NMR‐Solution Structures and Affinities for the Human Somatostatin G‐Protein‐Coupled Receptors hsst1–5 of CF3 Derivatives of Sandostatin® (Octreotide)

The previously reported (Helv. Chim. Acta 2008 , 91, 2035) derivatives of octreotide ( 1 ) with a (CF₃)‐Trp substitution, i.e., 3 , and with open‐chain structures, i.e., 2, 4 , and 5 , have been tested for their affinities to hsst_1–5 receptors and subjected to a detailed NMR analysis. Their affinities vary from 15 nM to 5 μM , as compared to 0.6 nM to 0.8 μM for octreotide itself (Table 1). This decreased bioactivity may have had to be expected for the open‐chain compounds 4 and 5 ; possible reasons for this decrease in the case of CF₃ derivative of octreotide, 3 , are discussed. NMR Analysis (Tables 2 and 3) provides evidence for increased dynamics of all new derivatives 2 – 5 . The dynamics of the octreotide molecule 1 was analyzed by (natural‐abundance) longitudinal ¹³C‐T₁‐relaxation time measurements (Table 4), from which the conclusion is drawn that the backbone of the macrocycle is rather rigid on the time scale of this method.     

Structure and magnetism in Fe-Gd based dinuclear and chain systems. The interplay of weak exchange coupling and zero field splitting effects

The synthesis and characterization of two Fe-Gd systems based on bpca(-) (Hbpca = bis(2-pyridilcarbonyl)amine) as bridging ligand is presented, taking the systems as a case study for structure-property correlations. Compound 1, [Fe(LS)(II)(μ-bpca)(2)Gd(NO(3))(2)(H(2)O)]NO(3)·2CH(3)NO(2), is a zigzag polymer, incorporating the diamagnetic low spin Fe(LS)(II) ion. The magnetism of 1 is entirely determined by the weak zero field splitting (ZFS) effect on the Gd(III) ion. Compound 2 is a Fe(III)-Gd(III) dinuclear compound, [Fe(LS)(III)(bpca)(μ-bpca)Gd(NO(3))(4)]·4CH(3)NO(2)·CH(3)OH, its magnetism being interpreted as due to the antiferromagnetic coupling between the S(Fe) = ? and S(Gd) = 7/2 spins, interplayed with the local ZFS on the lanthanide center. In both systems, the d-f assembly is determined by the bridging capabilities of the ambidentate bpca(-) ligand, which binds the d ion by a tridentate moiety with nitrogen donors and the f center by the diketonate side. We propose a spin delocalization and polarization mechanism that rationalizes the factors leading to the antiferromagnetic d-f coupling. Although conceived for compound 2, the scheme can be proposed as a general mechanism. The rationalization of the weak ZFS effects on Gd(III) by multiconfiguration and spin-orbit ab initio calculations allowed us to determine the details of the small but still significant anisotropy of Gd(III) ion in the coordination sites of compounds 1 and 2. The outlined methodologies and generalized conclusions shed new light on the field of gadolinium coordination magnetochemistry.     

Nanomolar inhibitors of AmpC beta-lactamase

beta-lactamases are the most widespread resistance mechanism to beta-lactam antibiotics, such as the penicillins and the cephalosporins. In an effort to combat these enzymes, a combination of stereoselective organic synthesis, enzymology, microbiology, and X-ray crystallography was used to design and evaluate new carboxyphenyl-glycylboronic acid transition-state analogue inhibitors of the class C beta-lactamase AmpC. The new compounds improve inhibition by over 2 orders of magnitude compared to analogous glycylboronic acids, with K(i) values as low as 1 nM. On the basis of the differential binding of different analogues, the introduced carboxylate alone contributes about 2.1 kcal/mol in affinity. This carboxylate corresponds to the ubiquitous C3(4)' carboxylate of beta-lactams, and this energy represents the first thermodynamic measurement of the importance of this group in molecular recognition by class C beta-lactamases. The structures of AmpC in complex with two of these inhibitors were determined by X-ray crystallography at 1.72 and 1.83 A resolution. These structures suggest a structural basis for the high affinity of the new compounds and provide templates for further design. The highest affinity inhibitor was 5 orders of magnitude more selective for AmpC than for characteristic serine proteases, such as chymotrypsin. This inhibitor reversed the resistance of clinical pathogens to the third generation cephalosporin ceftazidime; it may serve as a lead compound for drug discovery to combat bacterial resistance to beta-lactam antibiotics.     

Microcalorimetric study of thermal unfolding of lysozyme in water/glycerol mixtures: an analysis by solvent exchange model

Folded protein stabilization or destabilization induced by cosolvent in mixed aqueous solutions has been studied by differential scanning microcalorimetry and related to difference in preferential solvation of native and denatured states. In particular, the thermal denaturation of a model system formed by lysozyme dissolved in water in the presence of the stabilizing cosolvent glycerol has been considered. Transition temperatures and enthalpies, heat capacity, and standard free energy changes have been determined when applying a two-state denaturation model to microcalorimetric data. Thermodynamic parameters show an unexpected, not linear, trend as a function of solvent composition; in particular, the lysozyme thermodynamic stability shows a maximum centered at water molar fraction of about 0.6. Using a thermodynamic hydration model based on the exchange equilibrium between glycerol and water molecules from the protein solvation layer to the bulk, the contribution of protein-solvent interactions to the unfolding free energy and the changes of this contribution with solvent composition have been derived. The preferential solvation data indicate that lysozyme unfolding involves an increase in the solvation surface, with a small reduction of the protein-preferential hydration. Moreover, the derived changes in the excess solvation numbers at denaturation show that only few solvent molecules are responsible for the variation of lysozyme stability in relation to the solvent composition.     

2D MXenes as Perspective Immobilization Platforms for Design of Electrochemical Nanobiosensors

MXenes are a new group of 2D nanomaterials with fascinating properties including high electrical conductivity, hydrophilic nature, easily tunable structure and high surface area. This is why MXene modified interfaces are extremely promising for the preparation of sensitive electrochemical biosensors. While there are numerous reports on MXene‐based enzymatic biosensors for detection of a wide range of analytes, application of MXene for construction of affinity biosensors is in its infancy. The review article summarizes current state‐of the‐art in the field with a focus on MXene modifications needed for construction of robust and high performance MXene electrochemical biosensors.     

Seasonal trend of Anisakidae infestation in South Mediterranean bluefish

Abstract

A total of 1104 fish samples from markets of Sicily were analysed for the detection and species identification of Anisakidae nematodes. The preliminary analysis of the fish samples showed the presence of 2459 larvae. All the fish species revealed different prevalence of infestation, with a maximum of 100% for Lepidopus caudatus and a minimum of 4.5% in Sardina pilchardus. The 80% of the larvae examined by PCR-RFLP analysis belonged to Anisakis pegreffii species. The seasonal infestation trend of Anisakis was evaluated in all the fish sample examined. The results of the seasonal infestation trend showed a marked connection with the ecological aspects of the fish species examined. As far as we know, this work report for the first time important ecological aspects of Lepidopus caudatus specimens of South Mediterranean. This work could be useful to plan a seasonal fishing strategy aimed at reducing the health risks related to Anisakis.     

Computational study of alkynes insertion into metal-hydride bonds catalyzed by bimetallic complexes

Density Functional Theory investigations on the insertion mechanism of phenylacetylene into metal-hydride bonds in bimetallic (Pt,Os) catalysts have been carried out. The results obtained have been also compared with the non-reactive monometallic (Os-based) system, to elucidate the cooperative effects and to explain the observed absence of reactivity. The identified reaction path involves phenylacetylene coordination followed by the insertion into the metal-hydride bond, leading to the formation of the experimentally observed products. Both steps do not require large energies compatible with the experimental conditions. The comparison with the reaction path for the monometallic species gives some hints on the cooperative effects due to the presence of the second metal which is related to its role in the CO release for creating a coordination site for phenylacetylene and not in the insertion energetics. The calculations provide a detailed analysis of the reaction complexity and provide a rationale for the efficiency of the process.     

Ortho-spirocarbonates and ortho-spirothiocarbonates: synthesis, functionalization and coupling

This paper describes a new efficient synthesis of 2,2′-spirobi-(1,3-benzoxathiole) (1), 2,2′-spirobi-(1,3-benzodithiole) (2) and 2,2′-spirobi-(1,3-benzodioxole) (3). Compound 3 has been functionalized by means of metallation reaction followed by electrophilic quenching to give carboxylic acids, aldehydes and alcohols. Furthermore compound 3 was subjected to homo-coupling and its dimeric structure was determined by XRD analysis.     

Structural, spectroscopic and magnetic investigation of the LiFe1−xMnxPO4 (x=0-0.18) solid solution

Different solid state and sol-gel preparations of undoped and Mn substituted cathode material LiFePO₄ are investigated. Li₃PO₄, Fe₂P₂O₇ and Li₄P₂O₇ are detected and quantified by XRPD only in solid state synthesis. In addition, micro-Raman spectra reveal low amount of different iron oxides clusters. EPR data, combined with the results of magnetization measurements, evidence signals from Fe³⁺ ions in maghemite nanoclusters, and in Li₃Fe₂(PO₄)₃. The sol-gel synthesis, showing the lowest amount of impurity phases, seems the most suitable to obtain a promising cathode material. The structural refinement gives new insights into the cation distribution of the Mn doped triphylite structure: (i) about 85% of Mn²⁺ ions substitutes Fe²⁺, the remaining 15% being located on the Li site, thus suggesting a structural disorder also confirmed by EPR and micro-Raman results; (ii) Mn ions on the Li site are responsible for the observed slight cell volume expansion.