Mechanistic investigation of charge-remote and charge-driven fragmentation processes in 2,5-diphenyl-3,4-ethylenedioxythiophene diamidines.

RATIONALE: Diphenylfuran diamidines represent an important class of DNA minor groove binders of high therapeutic interest as antitumor and antibacterial agents. This study aimed to investigate fragmentation patterns in mass spectra of four diamidine derivatives with significant antitumor activity, in order to gain more insight into the structures and stability of their putative biological metabolites. METHODS: Compounds were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) using low-energy collision-induced dissociation (CID). Density functional theory calculations were performed to confirm the main fragmentation paths. RESULTS: The most abundant ion present in mass spectra is the doubly protonated molecule, whereas singly protonated molecules are present to a lesser extent. In the simplest compound, 2,5-bis(4-amidinophenyl)-3,4-ethylenedioxythiophene, the main fragmentation path was loss of ammonia, followed by loss of HCN where possible. The fragmentation of the N-alkyl derivatives (N-isopropyl-, N-isobutyl-, N-cyclopentyl-) includes competition between loss of alkene and the corresponding amine, followed by loss of another alkene and formation of fragment ions present in the pathway of the parent compound. CONCLUSIONS: The primary sites of fragmentations of investigated compounds are amidine groups, while breaking the core 3,4-ethylenedioxythiophene ring system does not take place. Fragmentation of the singly protonated molecule [M + H](+) occurs primarily on the charged side of the molecule, but a charge-remote process is energetically viable. The fragmentation mechanism of the alkyl derivatives revealed that singly and doubly protonated molecules cleave to the singly and doubly protonated molecules of the parent compound. Once formed, they are gradually transformed into nitrile. Copyright © 2016 John Wiley & Sons, Ltd.

Clinical application of autologous fibroblast cell culture in gingival recession treatment.

BACKGROUND AND OBJECTIVE: Gingival recession is defined as soft and hard tissue displacement resulting in root surface exposure. The optimal outcome of gingival recession treatment is complete, predictable and long-lasting root coverage with a significant level of tissue regeneration. Tissue engineering, which applies active regeneration principles, presents the contemporary treatment approach in the restitution and regeneration of lost tissues. The objective of the present study was to evaluate and compare the clinical results of application of an autologous fibroblast cell culture (AFCC) on a collagen matrix and a connective tissue graft (CTG) placed under a coronally advanced flap (CAF), in the treatment of single and multiple gingival recessions. MATERIAL AND METHODS: Eighteen patients from the Department of Periodontology, School of Dentistry, University of Belgrade, were randomly enrolled in this study. Inclusion criteria were the bilateral presence of Miller Class I or II single or multiple maxillary gingival recessions. A split-mouth design was used in the study. The experimental group was treated with AFCC on a collagen scaffold, which was placed under a CAF. The control group received a combination of CTG and CAF. Clinical parameters such as gingival recession coverage, keratinized tissue width, clinical attachment level and gingival index were recorded at baseline and at 12 mo postoperatively. The oral hygiene level was assessed by plaque index evaluation. Postoperative healing was evaluated through the healing index, recorded 1, 2 and 3 wk postoperatively. The final esthetic outcome was assessed using the mean root coverage esthetic score (RES). RESULTS: Statistically significant improvement of all parameters assessed was found compared with baseline. A statistically significant difference between groups was observed only in keratinized tissue width. Greater keratinized tissue width is still obtained with the use of CTG. Regarding the tissue-healing results, no statistically significant difference was achieved. The RES results were similar for both groups. CONCLUSIONS: Within the limitations of the present study, both procedures proved to be efficient in gingival recession treatment. AFCC, as a novel tissue-engineering concept and living cell-based therapy, proved to be a reliable and successful treatment concept.

Novel symmetric bis-benzimidazoles: Synthesis, DNA/RNA binding and antitrypanosomal activity.

The novel benzimidazol-2-yl-fur-5-yl-(1,2,3)-triazolyl dimeric series with aliphatic and aromatic central linkers was successfully prepared with the aim of assessing binding affinity to DNA/RNA and antitrypanosomal activity. UV-Visible spectroscopy, thermal denaturation showed interaction of heterocyclic bis-amidines with ctDNA. Circular dichroism studies indicated uniform orientation of heterocyclic bis-amidines along the chiral double helix axis, revealing minor groove binding as the dominant binding mode. The amidino fragment and 1,4-bis(oxymethylene)phenyl spacer were the main determinants of activity against Trypanosoma brucei. The bis-benzimidazole imidazoline 15c, which had antitrypanosomal potency in the submicromolar range and DNA interacting properties, emerged as a candidate for further structural optimization to obtain more effective agents to combat trypanosome infections.

Extended aromatic furan amidino derivatives as anti-Pneumocystis carinii agents.

The syntheses of nine new derivatives of 2, 5-bis[4-(N-alkylamidino)phenyl]furans with extended aromatic systems are reported. The interaction of these dicationic furans with poly(dA)poly(dT) and with the duplex oligomers d(CGCGAATTCGCG)2 and d(GCGAATTCGC)2 was determined by Tm measurement, and the effectiveness of these compounds against the immunosuppressed rat model of Pneumocystis carinii was evaluated. At a screening dose of 10 micromol/kg, 4 of the 12 amidino furans described here are more active than the parent compound 1. In general, extension of the aromatic system in the absence of a substitution of the amidino nitrogens resulted in higher affinity for DNA than the parent compound as judged by the larger DeltaTm values and suggests enhanced van der Waals interactions in the amidino furan-DNA complex. Three of the compounds, 3, 5, and 11, yield cysts counts of less than 0.1% of control when administered at a dosage of 10 micromol/kg. Compound 3, which does not have an extended aromatic system, is the most active derivative. Although a direct correlation between anti-P. carinii activity and DNA binding affinity was not observed, all compounds which have significant activity have large DeltaTm values.

Morphodynamic reactive response of the pineal gland of rats chronically exposed to stable strong magnetic field.

Mature male Wistar rats were affected by a strong magnetic field of 0.70 T for 20 min per day for 2 weeks. A short distance between the electromagnet pole expansions allowed interposition of one restrained animal only. The results obtained showed that the immobilization stress increased the peptidergic activity of both light and dark pinealocytes. In the animals exposed to the magnetic field, a dual morphodynamic response was observed: the peptidergic activity of light pinealocytes was obviously reduced versus the unimpaired stress-stimulated functional engagement of dark pinealocytes. The probability that the retina----pineal gland magnetoreceptor-magnetoeffector circuit is formed through the accentuation of the suppression of the noradrenaline input on light pinealocytes is discussed. It is also hypothesized that a potentially harmful bioeffect of a strong magnetic field could be manifested second to the impairment of the activity of light pinealocytes in organisms coping with stress.

An Aromatic Diamidine That Targets Kinetoplast DNA, Impairs the Cell Cycle in Trypanosoma cruzi, and Diminishes Trypomastigote Release from Infected Mammalian Host Cells

Trypanosoma cruzi is the etiological agent of Chagas disease, affecting approximately 10 million people in the Americas and with some 40 million people at risk. The objective of this study was to evaluate the anti-T. cruzi activity of three new diamidines that have a 3,4-ethylenedioxy extension of the thiophene core, designated MB17, MB19, and MB38. All three diamidines exhibited dose-dependent inhibition of epimastigote replication. The mechanisms of action of these diamidines were investigated. Unlike MB17 and MB19, MB38 exhibited a significant increase in the number of annexin-propidium iodide double-labeled cells compared to levels in control parasites. As MB17 had shown a lower 50% inhibitory concentration (IC50) against epimastigote growth, the mechanism of action of this drug was studied in more detail. MB17 triggered a decrease in the intracellular ATP levels. As a consequence, MB17 affected the genomic DNA and kinetoplast DNA (kDNA) and impaired the parasite cell cycle. Moreover, MB17 caused DNA fragmentation, with a more severe effect on kDNA than on nuclear DNA, resulting in dyskinetoplastic cells. MB17 was tested for toxicity and effectiveness for the treatment of infected CHO-K-1 cells, exhibiting a 50% cytotoxic concentration (CC50) of 13.47 +/- 0.37 mu Mand an IC50 of 0.14 +/- 0.12 mu Magainst trypomastigote release. MB17 also diminished the infection index by 60% at 0.5 mu M. In conclusion, despite belonging to the same family, these diamidines have different efficiencies. To summarize, MB17 was the most potent of these diamidines against epimastigotes, producing DNA damage preferentially in kDNA, impairing the parasite cell cycle, and decreasing the infection index and trypomastigote release from infected mammalian host cells, with a high selectivity index (SI) (< 90). These data suggest that MB17 could be an interesting lead compound against T. cruzi

Benzdiamidine.

The molecule of benzene-1,4-dicarboxamidine or benzdiamidine, C(8)H(10)N(4), reveals C(i) symmetry. Hydrogen bonds utilize the amino groups as double donors, whereas the imino groups act as double acceptors. The network formed is similar to that observed in the crystal packing of terephthalamide.

Electron impact mass spectra of some bis-(2-benzothiazolyl)furans and bis-(2-benzothiazolyl)thiophenes.

The electron impact mass spectra of some bis-(2-benzothiazolyl)furans and bis-(2-benzothiazolyl)thiophenes have been recorded and the identity of various ions in the mass spectra established. Compounds 1 and 2 present model substances and it is found that their fragmentation pathway is similar to the mono-(2-benzothiazoles). Compounds where the benzothiazolyl groups are directly substituted on the furan nuclei, but in different positions, exhibit two main pathways of fragmentation: fragmentation of the furan nucleus and fragmentation of the benzothiazole nucleus. Other compounds studied show specific fragmentation characteristic for divinyl furan compounds and for compounds with a phenyl substituent between two heterocyclic nuclei.

Mass spectral fragmentation patterns of some 2-methyl-3-furancarboxanilides and 2-methyl-3-furancarbothioanilides. II.

The electron impact mass spectra of some 2-methyl-3-furancarboxanilides and 2-methyl-3-furancarbothioanilides are discussed. Dominant peaks are formed by simple cleavage of a C-N bond in the anilides as well as in the thioanilides. Thioanilides show some additional fragmentation pathways recently reported which are not seen in the anilides. (T. Jagodzinski and M. Stobiecki, Org. Mass Spectrom., Vol. 25, p. 333 (1990)).

Mass spectral fragmentation patterns of some new 3,7-dichloro-benzo[1,2-b:4,5-b']dithiophene-2,6-dicarboxylic acid dianilides and 3,5-dichloro-dithieno[3,2-b:2',3'-d]thiophene-2,6-dicarboxylic acid dianilides. II.

The electron impact mass spectra of some benzo[1,2-b:4,5-b']dithiophene-2,6-dicarboxylic acid dianilides and dithieno[3,2-b:2',3'-d]thiophene-2,6-dicarboxylic acid dianilides are discussed. Dominant peaks in these dianilides are formed by the cleavage of a C-N bond on one side of an anilino group. These ions fragment further by the cleavage of a C-C bond on the other side of an anilino group and a CONRPhR' group may be lost directly. After loss of CO, the characteristic benzodithiophene radical cation, C10H2S2Cl2[symbol: see text], at m/z 256 and the dithienothiophene radical cation, C8S3Cl2[symbol: see text], at m/z 262 are formed from their respective precursor compounds.

Mass spectral fragmentation patterns of some new benzo[b]thiophene- and thieno[2,3-b]thiophene-2,5-dicarbonyldichlorides and -dicarbonyldianilides and anilidoquinolones.

The electron impact mass spectra of some benzo[b]thiophene- and thieno[2,3-b]thiophene-2,5-dicarbonyldichlorides, 2,5-dicarbonyldianalides, 9-anilido-benzo[b]thienyl[2,3-c]quinolones and 9-anilidothieno[4,5-b']thienyl[2,3-c]quinolones are discussed. Dominant peaks in dianilides are formed by cleavage of the C-N bond on one side of the anilido group, as well as on the anilido group itself in anilidoquinolones. These ions fragment further by the cleavage of a C-C bond in dianilides and the CONRPh group is lost directly, while the quinolonic part of the molecule in quinolones fragments with low probability. Characteristic fragment ions of dicarbonyldichlorides arise by the cleavage of the C-C1 bond.

Specific molecular recognition of mixed nucleic acid sequences: an aromatic dication that binds in the DNA minor groove as a dimer.

Phenylamidine cationic groups linked by a furan ring (furamidine) and related compounds bind as monomers to AT sequences of DNA. An unsymmetric derivative (DB293) with one of the phenyl rings of furamidine replaced with a benzimidazole has been found by quantitative footprinting analyses to bind to GC-containing sites on DNA more strongly than to pure AT sequences. NMR structural analysis and surface plasmon resonance binding results clearly demonstrate that DB293 binds in the minor groove at specific GC-containing sequences of DNA in a highly cooperative manner as a stacked dimer. Neither the symmetric bisphenyl nor bisbenzimidazole analogs of DB293 bind significantly to the GC containing sequences. DB293 provides a paradigm for design of compounds for specific recognition of mixed DNA sequences and extends the boundaries for small molecule-DNA recognition.

Structure-in vitro activity relationships of pentamidine analogues and dication-substituted bis-benzimidazoles as new antifungal agents.

Twenty analogues of pentamidine, 7 primary metabolites of pentamidine, and 30 dicationic substituted bis-benzimidazoles were screened for their inhibitory and fungicidal activities against Candida albicans and Cryptococcus neoformans. A majority of the compounds had MICs at which 80% of the strains were inhibited (MIC80s) comparable to those of amphotericin B and fluconazole. Unlike fluconazole, many of these compounds were found to have potent fungicidal activity. The most potent compound against C. albicans had an MIC80 of

Inhibition of the HIV-1 rev-RRE complex formation by unfused aromatic cations.

RNA viruses cause a wide range of human diseases. Development of new agents to target such viruses is an active area of research. Towards this goal, a series of diphenylfuran cations as potential inhibitors of the Rev-RRE complex have been designed and synthesized. Analysis of the interaction of the diphenylfurans with RRE and TAR RNA model systems by gel shift assays indicates that they exhibit both sequence and structure-dependent binding modes. Our results show a strong interaction between the diphenylfuran ring system and RRE bases, while the TAR interactions are much weaker with the compounds that are the best inhibitors of Rev-RRE.