Patrícia Martins

Supported iron(III)porphyrins pentafluorophenyl-derivatives as catalysts in epoxidation reactions by H2O2: the role of the silica-support and sulfonatophenyl residues in the activation of the peroxidic bond

Abstract Ionic Fe(III)porphyrins pentafluorophenyl-derivatives: 5,10,15-tris(pentafluorophenyl)-20-(4- N -methylpyridyl)porphyrin iron(III) ([Fe{M(4- N -MePy)TPFP}] 2+ ), 5,10,15-tris(4- N -methylpyridyl)-20-(pentafluorophenyl)porphyrin iron(III) ([Fe{T(4- N -MePy)MPFP}] 4+ ) and 5,10,15-tris(pentafluorophenyl)-20-(3-sulfonatophenyl)porphyrin iron(III) ([Fe{M(3-SO 3 P)TPFP}]) immobilised on silica gel (SiO 2 ) and modified silica with sulfonatophenyl (SiSO 3 − ), propylimidazole (IPG), sulfonatophenyl plus propylimidazole (SiSO 3 − (IPG)), propyltrimethylammonium (SiN + ) and propyltrimethylammonium plus propylimidazole (SiN + (IPG)) were studied in the epoxidation of ( Z )-cyclooctene by H 2 O 2 . The better yields of product, cis -epoxycyclooctane, were achieved with the catalytic systems, [Fe{M(4- N -MePy)TPFP}]-SiSO 3 (IPG), [Fe{M(3-SO 3 P)TPFP}]-IPG and [Fe{M(3-SO 3 P)TPFP}]-SiO 2 , where is more probable to have available sulfonatophenyl groups. That is, where there is no ionic binding Fe(III)porphyrin-support via sulfonatophenyl. A charge effect supplied by the available sulfonatophenyl residues and a more polar microenvironment provided by the silica-support promote the heterolytic cleavage of the OO bond, which is essential to obtain high yields of products in oxidation reactions. Effects of general acid–base catalysis, as occurs in enzymes, and higher reduction potential provided by electron-withdrawing groups, present on porphyrin ring or axial ligand, as recently reported by Nam and coworkers for homogeneous Fe(III)porphyrins, to promote the heterolysis of the OO bond are ruled out.

Characterization and catalytic activity of iron(III) mono(4-n-methyl pyridyl)-tris(halophenyl) porphyrins in homogeneous and heterogeneous systems

Abstract The synthesis, characterization and catalytic activity of the cationic iron porphyrins Fe[M(4-N-MePy)TDCPP]Cl2 and Fe[M(4-N-MePy)TFPP]Cl2 in the epoxidation of (Z)-cyclooctene by PhIO in homogeneous solution and supported on silica gel (SG), imidazole propyl gel (IPG) or SG modified with 2-(4-sulfonatophenyl)ethyl groups (SiSO3) have been accomplished. When supported on IPG, both cationic FeP bind to the support via Fe–imidazole coordination. Fe[M(4-N-MePy)TDCPP]IPG contains a mixture of low-spin bis-coordinated FeIIIP and high-spin mono-coordinated FeIIIP species, whereas Fe[M(4-N-MePy)TFPP]IPG only contains high-spin mono-coordinated FeIIIP. These FePIPG catalysts also contain FeIIP species, whose presence was confirmed by EPR spectroscopy using NO as a paramagnetic probe. Both cationic FePs coordinate to SG through Fe–O ligation and they are present as high-spin FeIIIP species. The cationic FePs supported on SiSO3− are also high-spin FeIIIP species and they bind to the support via electrostatic interaction between the 4-N-methylpyridyl groups and the SO3− groups present on the matrix. In homogeneous solution, both Fe[M(4-N-MePy)TDCPP]Cl2 and Fe[M(4-N-MePy)TFPP]Cl2 have similar catalytic activity to Fe(TDCPP)Cl and Fe(TFPP)Cl, leading to cis-epoxycyclooctane yields of 92%. When supported on inorganic matrices, both FePs lead to epoxide yields comparable to their homogeneous analogues and their anchoring enables catalyst recovery and re-use. Recycling of Fe[M(4-N-MePy)TDCPP]SiSO3− shows that this FeP maintains its activity in a second reaction.

Modulation of mouse embryonic stem cell proliferation and neural differentiation by the P2X7 receptor.

Background Novel developmental functions have been attributed to the P2X7 receptor (P2X7R) including proliferation stimulation and neural differentiation. Mouse embryonic stem cells (ESC), induced with retinoic acid to neural differentiation, closely assemble processes occurring during neuroectodermal development of the early embryo. Principal Findings P2X7R expression together with the pluripotency marker Oct-4 was highest in undifferentiated ESC. In undifferentiated cells, the P2X7R agonist Bz-ATP accelerated cell cycle entry, which was blocked by the specific P2X7R inhibitor KN-62. ESC induced to neural differentiation with retinoic acid, reduced Oct-4 and P2X7R expression. P2X7R receptor-promoted intracellular calcium fluxes were obtained at lower Bz-ATP ligand concentrations in undifferentiated and in neural-differentiated cells compared to other studies. The presence of KN-62 led to increased number of cells expressing SSEA-1, Dcx and β3-tubulin, as well as the number of SSEA-1 and β3-tubulin-double-positive cells confirming that onset of neuroectodermal differentiation and neuronal fate determination depends on suppression of P2X7R activity. Moreover, an increase in the number of Ki-67 positive cells in conditions of P2X7R inhibition indicates rescue of progenitors into the cell cycle, augmenting the number of neuroblasts and consequently neurogenesis. Conclusions In embryonic cells, P2X7R expression and activity is upregulated, maintaining proliferation, while upon induction to neural differentiation P2X7 receptor expression and activity needs to be suppressed.

A novel chlorin derivative of Meso-tris(pentafluorophenyl)-4-pyridylporphyrin: synthesis, photophysics and photochemical properties

Photodynamic therapy (PDT) is based on the accumulation of a photosensitizer, such as a porphyrin or a chlorin, in a malignant tissue after its administration. Chlorins exhibit photophysical properties similar to those of the porphyrin macrocycles, but with intensified and red-shifted Q bands, making chlorin-containing systems even better candidates for PDT. In this contribution, we report the synthesis of 5,10,15-tris(pentafluorophenyl)-20-(4-pyridyl)porphyrin, (2) and its transformation to the novel chlorin derivatives 4, (5,10,20-tris(pentafluorophenyl)-15-(4-pyridyl)-tetrahydro-1H- N-methyl-pyrrolo [3,4-b]porphyrin and 5, (5,10,15-tris(pentafluorophenyl)-20-(4-pyridyl)-tetrahydro-1H- N-methyl-pyrrolo[3,4-b]porphyrin) by 1,3-dipolar cycloaddition with an azomethine ylide. The new products have been characterized by UV-Vis, 1H NMR and FAB-MS. The photophysics, photochemical and photobleaching properties of chlorin 4 have been evaluated. Its quantum yield of photobleaching (fPb, mol Einstein-1) was 0.047±0.014. In order to demonstrate the production of 1O2 when 4 is used as a photosensitizer, uric acid tests have been carried out. The results indicate that chlorin 4 can be considered a promising photosensitizer in PDT.

Aminoterminal B-Type Natriuretic Peptide (NT-proBNP) in End-Stage Renal Failure Patients on Regular Hemodialysis: Does It Have Diagnostic and Prognostic Implications?

Background: Amino-terminal B-type natriuretic peptide (NT-proBNP) quantification is a useful cardiovascular diagnostic and prognostic test. In renal failure its use may have constraints, as it depends on renal clearance. We aimed to evaluate the clinical usefulness of NT-proBNP in hemodialysis (HD) patients. Methods: We measured NT-proBNP levels in 44 patients before and after a regular high-flux HD. Cardiac parameters were evaluated by echocardiography. Patients were followed up for 656.5 ± 476.4 days for the occurrence of hospital admission or death. Results: NT-proBNP levels decreased after HD (p < 0.0001) without correlation with ultrafiltration volume, Kt/V index, weight decrease or pulse pressure decrease. Pre- and post-HD NT-proBNP were similar in patients with and without left ventricular hypertrophy. Pre-HD levels were not significantly associated with prognosis, probably due to a type 2 error; post-HD NT- proBNP and NT-proBNP reduction ratio (RR) were predictive of the outcome by Kaplan-Meier analysis, but only RR remained associated with prognosis on multivariate regression analysis (hazard ratio 0.96; 95% confidence interval 0.93–0.99). Conclusion: Our results do not support the use of NT-proBNP in the diagnosis of left ventricular hypertrophy or volume status in HD patients, but suggest its utility in prognostic stratification. HD-related variation in NT-proBNP was associated with prognosis.

Unwanted effects: Is there a negative side of meditation? A multicentre survey

Objectives Despite the long-term use and evidence-based efficacy of meditation and mindfulness-based interventions, there is still a lack of data about the possible unwanted effects (UEs) of these practices. The aim of this study was to evaluate the occurrence of UEs among meditation practitioners, considering moderating factors such as the type, frequency, and lifetime duration of the meditation practices. Methods An online survey was developed and disseminated through several websites, such as Spanish-, English- and Portuguese-language scientific research portals related to mindfulness and meditation. After excluding people who did not answer the survey correctly or completely and those who had less than two months of meditation experience, a total of 342 people participated in the study. However, only 87 reported information about UEs. Results The majority of the practitioners were women from Spain who were married and had a University education level. Practices were more frequently informal, performed on a daily basis, and followed by focused attention (FA). Among the participants, 25.4% reported UEs, showing that severity varies considerably. The information requested indicated that most of the UEs were transitory and did not lead to discontinuing meditation practice or the need for medical assistance. They were more frequently reported in relation to individual practice, during focused attention meditation, and when practising for more than 20 minutes and alone. The practice of body awareness was associated with UEs to a lesser extent, whereas focused attention was associated more with UEs. Conclusions This is the first large-scale, multi-cultural study on the UEs of meditation. Despite its limitations, this study suggests that UEs are prevalent and transitory and should be further studied. We recommend the use of standardized questionnaires to assess the UEs of meditation practices.