Synthesis, spectral and thermal study on new Fe(III) complexes with N,N-dimethylbiguanide as antibacterial agents

New complexes [FeO(DMBG)]₂ and [Fe(DMBG)₂]Cl·0.5H₂O (HDMBG: N,N-dimethylbiguanide) have been synthesized and characterized by microanalytical, IR and UV–Vis data. Electronic spectra of the complexes are characteristic for a tetrahedral stereochemistry, whilst the modifications in the IR spectra indicate the presence of the DMBG anion as chelate. The thermal decomposition investigated in air by thermal analysis confirmed the proposed formulas for the complexes and provided information concerning the modifications during heating and also the thermodynamic effects accompanying them. The thermal transformations are complex, according to TG and DTG curves including dehydration, hydrochloric acid elimination, oxidative degradation and condensation of –C=N– unit. The final product of decomposition was iron (III) oxide as powder XRD indicates. Complexes were screened for their antimicrobial properties against Gram-positive, Gram-negative bacterial, as well as fungal pathogenic strains. The results indicate that Fe(III) complexes exhibit an improved antibacterial activity against S. aureus and E. coli strains in comparison with free biguanide. The Fe(III) complexes also inhibit the ability of S. aureus, B. subtilis, P. aeruginosa and E. coli strains to colonize the inert substratum, accounting for their possible use as anti-biofilm agents.     

Physico-chemical and thermal characterisation of new Co(II) complexes with pyrazole derivatives

Four new complexes having general formula [CoL₂(acr)₂] (L: 1H-pyrazole (Hpz) (1); 3-methyl-1H-pyrazole (3-Me-Hpz) (2); 4-methyl-1H-pyrazole (4-Me-Hpz) (3); 3,5-dimethyl-1H-pyrazole (Hdmpz) (4); acr: acrylato ion) were synthesised and characterised. The infrared and UV–vis spectral data indicate that these pyrazole derivatives act as unidentate while acrylato ions act as bidentate chelate ligands generating Co(II) complexes with octahedral stereochemistry. TG experiments revealed the nature of complex species as anhydrous and confirmed those compositions. The biological assays revealed a good activity against Bacillus subtilis for all complexes.     

Frequency effects on the surface coverage of nitrophenyl films ultrasonically grafted onto indium tin oxide

The covalent attachment of various organic molecules on conductive supports including indium tin oxide (ITO) using diazonium chemistry has been known for many years. A commonly used method to achieve this is the electrochemical reduction of diazonium compounds leading to radicals, followed by binding of the radicals to the support. In the present report, an alternative method using ultrasound at different frequencies (20, 582, 863, and 1142 kHz) to induce the surface grafting of nitrobenzene diazonium onto an ITO surface is described. It is shown that the grafting on ITO is more efficient in the lower ultrasonic frequency range that is ascribed to changes in the balance between the physical and chemical effects of cavitation with frequency. Both the physical and chemical effects of cavitation play important roles at all frequencies, but at high ultrasound frequencies, the physical effects are relatively small. At 20 kHz, the physical component, including mass transport, is larger than at higher frequencies, and mechanisms based on these observations have been proposed. Ultrasonic grafting has an advantage over electrografting in that it may provide more control over surface coverage, thus it is suggested that the ultrasonic method is used where the surface concentration of the organic layer must be controlled.     

A deep insight into the mechanism of the acid‐catalyzed rearrangement of the Z‐phenylhydrazone of 5‐amino‐3‐benzoyl‐1,2,4‐oxadiazole in a non‐polar solvent

The conversion of the Z‐phenylhydrazone of 5‐amino‐3‐benzoyl‐1,2,4‐oxadiazole ( 1a ) into the relevant 1,2,3‐triazole ( 2a) has been quantitatively studied in toluene in the presence of several halogenoacetic acids ( HAA s, 3a – h ). Again, the occurrence of two reaction pathways has been pointed out: they require one or two moles of acid, respectively, thus repeating the situation previously observed in the presence of trichloroacetic acid. The observed rate constant ratios (k_III/k_II) are only slightly affected by the nature of the acid used. To gain a deeper insight into the action of the acids used we have measured the association constants of the HAA s ( 3a – h) with 4‐nitroaniline ( 4 ) in toluene. Also in this case, the formation of two complexes requiring one (K₂) or two (K₃) moles of acid has been evidenced, but now the K₃/K₂ ratios are significantly affected by the strength of the acid examined. The variation of the K₃/K₂ ratios larger than those concerning the k_III/k_II ratios appears useful to enlighten the very nature of the acid‐catalyzed pathways in toluene, which has been elucidated also carrying out the rearrangement in the presence of mixtures of tribromo‐ and trichloro‐acetic acids at different concentrations. Copyright © 2010 John Wiley & Sons, Ltd.     

Isomerization and rearrangement of (E)‐ and (Z)‐phenylhydrazones of 3‐benzoyl‐5‐phenyl‐1,2,4‐oxadiazole: evidence for a ‘new’ type of acid‐catalysis by copper(II) salts in mononuclear rearrangement of heterocycles

A kinetic investigation in methanol of the title reaction has evidenced the occurrence of two processes: the 1‐ E 1‐ Z isomerization and the rearrangement of the (Z)‐isomer into the relevant 4‐benzoylamino‐2,5‐diphenyl‐1,2,3‐triazole ( 1‐ Z → T ). The latter reaction is in line with the ability of the (Z)‐phenylhydrazones of 3‐benzoyl‐1,2,4‐oxadiazoles to undergo the so called mononuclear rearrangement of heterocycles (MRH). The occurrence of both the examined reactions is dependent on a Lewis‐acid‐catalysis. The obtained results have shown the possibility of a ‘new’ type of acid‐catalysis (bifunctional catalysis by Lewis salts) in the MRH. This catalysis operates through a completely different mechanism with respect to the one recently observed, and deeply investigated, in the presence of protic acids for the (Z)‐phenylhydrazone of 5‐amino‐3‐benzoyl‐1,2,4‐oxadiazole, in both dioxane/water and toluene, for which the catalytic process was dependent on the protonation of N(4) ring‐nitrogen of the 1,2,4‐oxadiazole. As a matter of fact, the copper salts seem able to interact with the >C?N? NH? C₆H₅ moiety, yielding adducts which, in some cases, are prone to both isomerize and rearrange. Therefore, a similar behaviour in some manner parallel to that already observed in benzene in the presence of aliphatic amines (base‐catalysis) has been evidenced. Copyright © 2008 John Wiley & Sons, Ltd.     

Functional MRI changes in the central motor system in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a multisystemic disease involving multiple organ systems including central nervous system (CNS) and muscles. Few studies have focused on the central motor system in DM1, pointing to a subclinical abnormality in the CNS. The aim of our study was to investigate patterns of cerebral activation in DM1 during a motor task using functional MRI (fMRI). Fifteen DM1 patients, aged 20 to 59 years, and 15 controls of comparable age were scanned during a self-paced sequential finger-to-thumb opposition task of their dominant right hand. Functional MRI images were analyzed using SPM99. Patients underwent clinical and genetic assessment; all subjects underwent a conventional MR study. Myotonic dystrophy type 1 patients showed greater activation than controls in bilateral sensorimotor areas and inferior parietal lobules, basal ganglia and thalami, in the ipsilateral premotor area, insula and supplementary motor area (corrected P<.05). Analysis of the interaction between disease and age showed that correlation with age was significantly greater in patients than in controls in bilateral sensorimotor areas and in contralateral parietal areas. Other clinical and MR characteristics did not correlate with fMRI. Functional changes in DM1 may represent compensatory mechanisms such as reorganization and redistribution of functional networks to compensate for ultrastructural and neurochemical changes occurring as part of the accelerated aging process.     

Focus on the Protein Fraction of Sports Nutrition Supplements

Increasing awareness of balanced diet benefits is boosting the demand for high-protein food and beverages. Sports supplements are often preferred over traditional protein sources to meet the appropriate dietary intake since they are widely available on the market as stable ready-to-eat products. However, the protein components may vary depending on both sources and processing conditions. The protein fraction of five commercial sports supplements was characterized and compared with that of typical industrial ingredients, i.e., whey protein concentrates and isolates and whey powder. The capillary electrophoresis profiles and the amino acid patterns indicated that, in some cases, the protein was extensively glycosylated and the supplemented amino acids did not correspond to those declared on the label by manufacturers. The evaluation by confocal laser scanning microscopy evidenced the presence of large aggregates mainly enforced by covalent crosslinks. The obtained findings suggest that, beside composition figures, provisions regarding sports supplements should also consider quality aspects, and mandatory batch testing of these products would provide more reliable information to sport dieticians.     

Electrode-Potential-Driven Dissociation of N-Heterocycle/BF3 Adducts: A Possible Manifestation of the Electro-Inductive Effect

Recently, non-Faradaic effects were used to modify the electronic structure and reactivity of electrode-bound species. We hypothesize that these electrostatic perturbations could influence the chemical reactivity of electrolyte species near an electrode in the absence of Faradaic electron transfer. A prime example of non-Faradaic effects is acid-base dissociation near an interface. Here, we probed the near-electrode dissociation of N-heterocycle-BF₃ Lewis adducts upon electrode polarization, well outside of the redox potential window of the adducts. Using scanning electrochemical microscopy and confocal fluorescence spectroscopy, we detected a potential-dependent depletion of the adduct near the electrode. We propose an electro-inductive effect where a more positive potential leads to electron withdrawal on the N-heterocycle. This study takes a step forward in the use of electrostatics at electrochemical interfaces for field-driven electrocatalytic and electro-synthetic processes.