Bischelated complexes of a dithiocarbazate <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">S</Emphasis> Schiff base ligand: synthesis,characterization and antimicrobial activities

The N,S bidentate proligand S-hexyl-β-N-(4-methoxybenzylidene)dithiocarbazate (HL), obtained by condensation of S-hexyldithiocarbazate with 4-methoxybenzaldehyde, has been used to synthesize six metal complexes, namely NiL₂, CuL₂, ZnL₂, CdL₂, PdL₂ and PbL₂, which have been characterized by physicochemical techniques and spectroscopic methods. Single crystal structural analyses for NiL₂, CuL₂ and PdL₂ show that these are square-planar complexes with each metal bischelated by the Schiff base in its deprotonated monoanionic form. In all three cases, the ligands show a trans configuration, although they crystallize in different space groups. All the metal complexes with the exception of the nickel derivative show a significant decrease in fluorescence intensity with respect to the free proligand HL. Free HL and all six complexes were tested for antibacterial activity against three pathogenic gram-negative organisms. The metal complexes show moderate although diverse activities; however, free HL as well as the copper(II) complex did not reveal any antibacterial activity against the tested organisms.     

In vitro study of iron coordination properties,anti-inflammatory potential,and cytotoxic effects of <Emphasis Type="Italic">N</Emphasis>-salicylidene and <Emphasis Type="Italic">N</Emphasis>-vanillidene anil Schiff bases

N-Salicylidene and N-vanillidene anil Schiff bases SB-1–5 were evaluated for their iron-coordinating properties. For this purpose, reactions with Fe(III) chloride were performed. The obtained results showed that salicylaldehyde bases SB-1 and SB-2 are the best coordinating ligands among the investigated SBs. The corresponding complexes are obtained in good yield and investigated using UV–Vis spectrophotometry and IR spectroscopy. The inhibitory potential of SB-1–5 against iron-containing enzyme lipoxygenase (LOX) was also tested. Salicylidene bases exerted better activity then vanilliden. The cytotoxic in vitro activities against human breast carcinoma MDA-MB-231 and human colon carcinoma HCT-116 cell lines were determined. Based on these results, SB-1 and SB-2 can be considered as interesting compounds for further in vivo investigations.     

Synthesis of <Emphasis Type="Italic">P,N</Emphasis>-protected phosphinic pseudoprolylglycine block

The phosphine block N-Cbz-Pro-ψ[P(O)(OAd)CH₂]-GlyOH has been synthesized for subsequent peptide assembly. A procedure has been proposed for the preparation of phosphorus prolylglycine isostere by three-center two-component amide version of the Kabachnik–Fields reaction. A combination of amide and carbonyl fragments in the molecule of 4-N-Cbz-aminobutyraldehyde makes it possible to accomplish cyclization with generation in situ of a cyclic pyrrolidine Schiff base, followed by Arbuzov phosphorylation of the latter with diacetyl 2-(ethoxycarbonyl)ethyl phosphonite generated in situ.     

Synthesis and Characterization of Disulfide-Schiff Base Derivatives and <Emphasis Type="Italic">in vitro</Emphasis> Investigation of Their Antibacterial Activity Against Multidrug-Resistant <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis> Isolates: A New Study

In this study two different methods without a catalyst and with a CeO₂ nano catalyst were used for the synthesis of dimeric disulfide-Schiff bases. The dimeric disulfide-Schiff base derivatives were characterized by FT-IR, NMR, and MS spectra, and elemental analysis. The disulfide-Schiff bases and their derivatives 2–5c were screened for in vitro antibacterial activity against 40 multidrug-resistant strains of Acinetobacter baumannii, and their minimum inhibitory concentrations were determined. Most of products exhibited high antibacterial activity against Acinetobacter baumannii.     

Analysis of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> PAO1 Biofilm Protein Profile After Exposure to <Emphasis Type="Italic">n</Emphasis>-Butanolic <Emphasis Type="Italic">Cyclamen coum</Emphasis> Extract Alone and in Combination with Ciprofloxacin

Pseudomonas aeruginosa biofilm-related infections are the major cause of premature death in cystic fibrosis patients. Strategies to induce biofilm dispersal are of interest, because of their potential in preventing biofilm-related infections. Our previous work demonstrated that n-butanolic Cyclamen coum extract with ciprofloxacin could eliminate 1- and 3-day-old P. aeruginosa PAO1 biofilms. To gain new insights into the role of C. coum extract and its synergistic effect with ciprofloxacin in eliminating P. aeruginosa PAO1 biofilms, two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry-based protein identification were used. Changes in the bacterial protein expression were analyzed when 3-day-old biofilm cells were exposed to the C. coum extract alone and in combination with ciprofloxacin. Proteins involved in alginate biosynthesis, quorum sensing, adaptation/protection, carbohydrate and amino acid metabolism showed a weaker expression in the C. coum extract-ciprofloxacin-treated biofilm cells compared to those in the untreated cells. Interestingly, the proteome of C. coum extract-ciprofloxacin-treated biofilm revealed more resemblance to the planktonic phenotype than to the biofilm phenotype. It appears that saponin extract in combination with ciprofloxacin causes biofilm disruption due to several mechanisms such as motility induction, cell envelope integrity perturbation, stress protein expression reduction, and more importantly, signal transduction perturbation. In conclusion, exposure to a combination of biofilm dispersal such as saponin extract and antimicrobial agents may offer a novel strategy to control preestablished, persistent P. aeruginosa biofilms and biofilm-related infections.     

Synthesis and properties of manganese complexes of <Emphasis Type="Italic">meso</Emphasis>-tetraphenyltetrabenzoporphyrin

The coordination of meso-tetraphenyltetrabenzoporphyrin and metal exchange of its Cd(II) complex with manganese(II) chloride and acetate in DMF and a chloroform–methanol mixture have been studied by spectrophotometry. The Mn(III) chloride and acetate acido complexes formed in these reactions have been isolated and characterized. The dissolution of the synthesized complexes in DMF in the presence of solid KOH gives Mn(II) meso-tetraphenyltetrabenzoporphyrinate.     

Sensitive fluorescent imaging of <Emphasis Type="Italic">Salmonella enteritidis</Emphasis> and <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> using a polyvalent directed peptide polymer

The authors describe three fluorescein-conjugated peptides generated by cell-phage display for use as a diagnostic probes for fluorescent detection and imaging of Salmonella enteritidis and Salmonella typhimurium. The authors also designed a polyvalent-directed peptide polymer synthesized with poly-D-lysine and bifunctional succinimidyl 3-(2-pyridyldithio)propionate with an affinity and sensitivity that is higher by more than an order of magnitude compared to single peptides due to multiple binding site interactions. In order to establish a diagnostic system for food poisoning, imaging analysis was performed using fluorescence microscopy. The limit of detection of the diagnostic system based on polyvalent directed peptide interaction is 10² colony-forming units per mL for Salmonella.

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Graphical abstract Schematic of a fluorescent method for detection and imaging of Salmonella enteritidis and Salmonella typhimurium by using a fluorescein labeled polyvalent-directed peptide polymer (PDPP) with a high affinity and sensitivity as a diagnostic probe. The system uses a microplate reader and was applied to the detection of food poisoning.

     

Synthesis and antibacterial activity of new <Emphasis Type="Italic">N</Emphasis>-substituted 7-amino-4-methyl-2<Emphasis Type="Italic">H</Emphasis>-chromen-2-ones

N-Substituted 7-amino-4-methyl-2H-chromen-2-ones containing one or two functionalized azole or azine moieties were synthesized. The structures of all synthesized compounds were confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy. Some of the synthesized compounds exhibited weak antibacterial activity against Rhizobium radiobacter, Escherichia coli, and Xanthomonas campestris.     

Synthesis,characterization and X-ray crystal structures of two non-molecular coordination polymers of manganese(II) and copper(II) with <Emphasis Type="Italic">N</Emphasis>-(2-pyridylmethyl)-<Emphasis Type="SmallCaps">l</Emphasis>-alanine and isothiocyanato ligands

The reduced Schiff base, N-(2-pyridylmethyl)-l-alanine (Pyala), has been prepared and used as a ligand for the synthesis of two new non-centrosymmetrical isothiocyanate mixed-ligand coordination polymers, [MnPyalaSCN] _n and [CuPyalaSCN] _n . Pyala and the metal complexes were characterized by physico-chemical and spectroscopic methods. The single-crystal X-ray structures of the complexes reveal both compounds to be non-molecular coordination polymers which crystallize in the orthorhombic system. The ligand acts as a bridge between two metal centres in both compounds, forming two six-membered rings around each Mn atom and two five-membered rings around each Cu centre. The 1D chains are assembled via N–H?O, N–H?S hydrogen bonds and S–S interactions building 3D helical supramolecular networks in both compounds. Packing of the polymers of both compounds along the b-axis gives chiral channels.     

Synthesis of ethyl (2<Emphasis Type="Italic">E</Emphasis>,4<Emphasis Type="Italic">E</Emphasis>)- and (2<Emphasis Type="Italic">E</Emphasis>,4<Emphasis Type="Italic">Z</Emphasis>)-5-chloropenta-2,4-dienoates

An efficient synthetic approach to 2E,4E and 2E,4Z isomers of ethyl 5-chloropenta-2,4-dienoate has been developed on the basis of one-pot oxidation–olefination of readily accessible (E)- and (Z)-3-chloroprop-2-en-1-ols by the action of barium manganate and ethyl (triphenyl-λ⁵-phosphanylidene)acetate.     

Splitting of the <Emphasis Type="Italic">d</Emphasis><Superscript><Emphasis Type="Italic">N</Emphasis></Superscript> atomic states in icosahedral 3<Emphasis Type="Italic">d</Emphasis> metal endofullerenes M@C<Subscript>60</Subscript>

Group-theoretical and quantum-chemical investigations of the spectrum of low-lying excited states have been performed by the ROHF and FCI-RAS (Full CI in Restricted Active Space) methods for 3d metal endofullerenes (MEFs) M@C₆₀ (M =Mn, Cr, and Fe) in different charged states. The major purpose of this study is quantum-chemical verification of the anomalous (“non-Bethe’s”) character of splitting of the d ^N atomic states in an electrostatic field with icosahedral symmetry, predicted previously within the theory of integral invariants theory. The interrelation between the integral invariants theory and the quantumchemical methods applied in this work is considered in detail. Our calculations suggest that the d ^N atomic states in the icosahedral field generated by fullerene C60 (I _h ) on a metal atom (ion) remain non-split for different charged states of the metal and C₆₀. Reasons for this phenomenon and other possible approaches to verification of the prediction are discussed. It is demonstrated that the d ^N states of the encapsulated metal are split in icosahedral 3d MEFs only under very strong compression of these structures.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-Allyl- and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Diallyltrifluoromethanesulfonamides with Carboxylic Acid Amides under Oxidizing Conditions

Reactions of acetamide and benzamide with N-allyltrifluoromethanesulfonamide in the presence of t-BuOCl–NaI afforded exclusively 2,5-bis(chloromethyl)-1,4-bis(trifluoromethanesulfonyl)piperazine. Analogous reaction with N,N-diallyltrifluoromethanesulfonamide gave mixed halogenation product at only one C=C double bond of the substrate.     

Synthesis and antibacterial evaluation of novel Schiff base derivatives containing 4(3<Emphasis Type="Italic">H</Emphasis>)-quinazolinone moiety

A series of novel Schiff base derivatives containing 4(3H)-quinazolinone moiety were synthesised and their antibacterial activities against tobacco and tomato bacterial wilts evaluated in vitro. Out of the synthesised compounds, 5g, 5j, 5n, 5m and 5p exhibited excellent antibacterial activities against tobacco bacterial wilt, with half maximal effective concentrations (EC50): 160.34, 158.03, 125.94, 148.09 and 133.67 (all in εg mL^?1), respectively, which were better than the EC50 of thiodiazole–copper (216.70 εg mL^?1). Compounds 5j, 5n and 5o also showed good antibacterial activities against tomato bacterial wilt, with EC50 of 95.20, 90.03 and 83.21 (all in εg mL^?1) respectively, which were better than the EC50of thiodiazole–copper (99.80 εg mL^?1). These compounds may prove to be useful as potential antibacterial agents.     

Properties and <Emphasis Type="Italic">N</Emphasis>-glycosylation of recombinant endoglucanase II from <Emphasis Type="Italic">Penicillium verruculosum</Emphasis>

Cellulases are the main components of enzyme complexes used in biotransformation processes of plant raw materials into valuable commercial products. Endoglucanase II (EG II) from the Penicillium verruculosum fungus was cloned into Penicillium canescens. The homogeneous recombinant EGII form is isolated and its properties are studied in comparison with the native enzyme. The N-glycosylation sites and the structure of the N-linked glycans are been determined using mass spectrometry. The biochemical and catalytic properties, as well as the N-glycosylation type of the obtained recombinant EGII form, appear to be close to the native enzyme. At the two potential N-glycosylation sites (N42 and N194) of both forms of the enzyme, N-linked high mannose glycans (or their enzymatic “trimming” products) according to the general formula (Man)_1–9(GlcNAc)₂ are detected. No glycosylation is found at the third potential site (N19).     

<Emphasis Type="Italic">CrMAPK3</Emphasis> regulates the expression of iron-deficiency-responsive genes in <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

Background

Under iron-deficient conditions, Chlamydomonas exhibits high affinity for iron absorption. Nevertheless, the response, transmission, and regulation of downstream gene expression in algae cells have not to be investigated. Considering that the MAPK pathway is essential for abiotic stress responses, we determined whether this pathway is involved in iron deficiency signal transduction in Chlamydomonas.

Results

Arabidopsis MAPK gene sequences were used as entry data to search for homologous genes in Chlamydomonas reinhardtii genome database to investigate the functions of mitogen-activated protein kinase (MAPK) gene family in C. reinhardtii under iron-free conditions. Results revealed 16 C. reinhardtii MAPK genes labeled CrMAPK2–CrMAPK17 with TXY conserved domains and low homology to MAPK in yeast, Arabidopsis, and humans. The expression levels of these genes were then analyzed through qRT-PCR and exposure to high salt (150 mM NaCl), low nitrogen, or iron-free conditions. The expression levels of these genes were also subjected to adverse stress conditions. The mRNA levels of CrMAPK2, CrMAPK3, CrMAPK4, CrMAPK5, CrMAPK6, CrMAPK8, CrMAPK9, and CrMAPK11 were remarkably upregulated under iron-deficient stress. The increase in CrMAPK3 expression was 43-fold greater than that in the control. An RNA interference vector was constructed and transformed into C. reinhardtii 2A38, an algal strain with an exogenous FOX1:ARS chimeric gene, to silence CrMAPK3. After this gene was silenced, the mRNA levels and ARS activities of FOX1:ARS chimeric gene and endogenous CrFOX1 were decreased. The mRNA levels of iron-responsive genes, such as CrNRAMP2, CrATX1, CrFTR1, and CrFEA1, were also remarkably reduced.

Conclusion

CrMAPK3 regulates the expression of iron-deficiency-responsive genes in C. reinhardtii.

     

Solution Thermodynamics of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis><Superscript>/</Superscript>-Ethylenebis-(salicylideneiminato)-diaquochromium(III) Chloride in Aqueous Dimethylsulphoxide

The densities, viscosities and refractive indices of N,N ^/-ethylene-bis(salicylideneiminato)-diaquochromium(III) chloride, [Cr(salen)(H₂O)₂]Cl, in aqueous dimethylsulfoxide (DMSO) with different mass fractions (w ₂ = 0.20, 0.40, 0.60, 0.80 and 1.00) of DMSO were determined at 298.15, 308.15 and 318.15 K under atmospheric pressure. From measured densities, viscosities and refractive indices the apparent molar volumes (V _φ ), standard partial molar volume (V _φ ⁰ ), the slope (S _V ^* ), standard isobaric partial molar expansibility (φ _E ⁰ ) and its temperature dependence (?φ _E ⁰ /?T) _p , the viscosity B-coefficient, its temperature dependence (?B/?T), solvation number (S _n ) and apparent molar refractivity (R _D ^φ ), etc., were calculated and discussed on the basis of ion–ion and ion–solvent interactions. These results revealed that the solutions are characterized by ion–solvent interactions rather than by ion–ion interactions and the complex behaves as a long range structure maker. Thermodynamics of viscous flow was discussed in terms of transition state theory.     

Coordination Polyhedra MC<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (M Is <Emphasis Type="Italic">s</Emphasis>-Metal Atom) in Crystal Structures

The crystallochemistry of compounds containing s-metal atoms in the carbon environment has been analyzed using the method of Voronoi–Dirichlet intersecting sectors and polyhedra. The chemical nature of the s metal has been found to affect the characteristics of the Voronoi–Dirichlet polyhedra. It is shown that the volume of Voronoi–Dirichlet polyhedron is practically independent of the coordination number of the s-metal atom.     

Viscosities and Surface Tensions of Phenetole with <Emphasis Type="Italic">N</Emphasis>-Methyl-2-pyrrolidone, <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylformamide and Tetrahydrofuran Binary Systems at Three Temperatures

Viscosities, η, and surface tensions, σ, of binary systems of phenetole (ethoxy benzene or ethyl phenyl ether) with N-methyl-2-pyrrolidone, N,N-dimethylformamide or with tetrahydrofuran were measured over the entire mole fraction range and at (298, 303 and 308) K. The experimental data was used to compute the deviations in viscosity, Δη, and surface tension, Δσ. Values of the excess Gibbs energy of activation G*^E, surface entropy S _σ and surface enthalpy H _σ were calculated. Viscosity data of the binary systems were calculated using the Grunberg and Nissan and the three-body and four-body McAllister correlations. The Redlich–Kister method was used for evaluation of coefficients and standard deviations for Δη, Δσ and G*^E. The results were interpreted in terms of the probable effect of molecular interactions between components as well as polarity.     

Synthesis and in vitro antibacterial evaluation of 6-substituted 4-amino-pyrazolo[3,4-<Emphasis Type="Italic">d</Emphasis>]pyrimidines

Pyrazolo[3,4-d]pyrimidines are one of the most important classes of fused heterocyclic compounds which exhibit a broad range of biological and medicinal properties. They are known as anticancer, antifungal, antibacterial, antiviral and anti-inflammatory agents. In this study, some new 6-substituted 4-amino-pyrazolo[3,4-d]pyrimidine derivatives were prepared via reaction of 5-amino-3-methyl-1-phenyl-1H-pyrazole-4-carbonitrile with various nitriles in the presence of sodium ethoxide as catalyst. The inhibitory properties of synthesized compounds were studied according to CLSI guidelines against some pathogenic bacteria including four gram-positive strains (Streptococcus pyogenes, Staphylococcus aureus, Bacillus cereus and Bacillus subtilis subsp. spizizenii) and three gram-negative strains (Pseudomonas aeruginosa, Shigella flexneri and Salmonella enterica subsp. enterica). The antibacterial effects of all derivatives were compared with those of antibiotics belonging to different classes. The values were reported as inhibition zone diameter (IZD), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The effect of substituents on the biological activity of derivatives was discussed as well. The inhibitory effect of compound 6a, was shown to be the most, with MIC values in the range of 32–4096 μg/mL. Since most of the synthesized compounds were effective against Streptococcus pyogenes and Pseudomonas aeruginosa, they can be considered as inhibitors of these two bacteria.     

Synthesis of amino acid conjugates of glycyrrhizic acid using <Emphasis Type="Italic">N</Emphasis>-hydroxyphthalimide and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-dicyclohexylcarbodiimide

Synthesis of amino acid conjugates of glycyrrhizic acid with the use of N-hydroxyphthalimide, N,N'-dicyclohexylcarbodiimide, and tert-butyl esters of L-amino acids (valine, isoleucine, phenylalanine, and methionine) was performed followed by deprotection with trifluoroacetic acid. The target amino acid conjugates were isolated by column chromatography on silica gel in 40–45% yield. The structure of the prepared compounds was confirmed by IR and ¹³C NMR spectroscopy.