Electron Spin-Dependent Electrocatalysis for the Oxygen Reduction Reaction in a Chiro-Self-Assembled Iron Phthalocyanine Device.

The chiral-induced spin selectivity effect (CISS) is a breakthrough phenomenon that has revolutionized the field of electrocatalysis. We report the first study on the electron spin-dependent electrocatalysis for the oxygen reduction reaction, ORR, using iron phthalocyanine, FePc, a well-known molecular catalyst for this reaction. The FePc complex belongs to the non-precious catalysts group, whose active site, FeN4, emulates catalytic centers of biocatalysts such as Cytochrome c. This study presents an experimental platform involving FePc self-assembled to a gold electrode surface using chiral peptides (L and D enantiomers), i.e., chiro-self-assembled FePc systems (CSAFePc). The chiral peptides behave as spin filters axial ligands of the FePc. One of the main findings is that the peptides' handedness and length in CSAFePc can optimize the kinetics and thermodynamic factors governing ORR. Moreover, the D-enantiomer promotes the highest electrocatalytic activity of FePc for ORR, shifting the onset potential up to 1.01 V vs. RHE in an alkaline medium, a potential close to the reversible potential of the O2 /H2 O couple. Therefore, this work has exciting implications for developing highly efficient and bioinspired catalysts, considering that, in biological organisms, biocatalysts that promote O2 reduction to water comprise L-enantiomers.

Comparison of the catalytic activity for O2 reduction of Fe and Co MN4 adsorbed on graphite electrodes and on carbon nanotubes.

We have compared the electrocatalytic activity of several substituted and unsubstituted Co and Fe N4-macrocyclic complexes (MN4) for the electro-reduction of oxygen with the complexes directly adsorbed on the edge plane of pyrolytic graphite or adsorbed on carbon nanotubes (CNTs). In the presence of CNTs, one order of magnitude higher surface concentrations of MN4 catalysts per geometric area unit could be adsorbed leading to a lower overpotential for the oxygen electro-reduction and activities in the same order of magnitude as the commercially available Pt/C catalysts in basic pH. From Koutecky-Levich regression analysis, the total number of electrons transferred was approximately 2 for all the Co complexes and 4 for all the Fe ones, both in the presence and in the absence of the carbon nanotubes. Furthermore, the Tafel slopes did not vary due to the presence of the CNTs and presented values in the range of -0.06 V decade-1 for the CoN4 compounds and in the range of -0.04 V decade-1 for FeN4. When plotting the log of kinetic current densities (i.e. log jk) at a constant potential for each complex divided by the surface concentration Γ, and the number of electrons transferred n for the ORR for each catalyst, versus the difference between the redox potential of the metal active site of the Co(ii)/(i) or Fe(iii)/(ii) catalyst and the reversible potential of the reaction they promote, the catalytic activity increases when the formal potential of the complex becomes more positive and the data obtained with complexes adsorbed on graphite are in agreement with the data obtained when using CNTs indicating that the increase in jk when CNTs are present is only due to an increase in the number of active sites per geometric area of the electrode.

The Phosphate Inhibition Paradigm: Host and Fungal Genotypes Determine Arbuscular Mycorrhizal Fungal Colonization and Responsiveness to Inoculation in Cassava With Increasing Phosphorus Supply.

A vast majority of terrestrial plants are dependent on arbuscular mycorrhizal fungi (AMF) for their nutrient acquisition. AMF act as an extension of the root system helping phosphate uptake. In agriculture, harnessing the symbiosis can potentially increase plant growth. Application of the AMF Rhizophagus irregularis has been demonstrated to increase the yields of various crops. However, there is a paradigm that AMF colonization of roots, as well as the plant benefits afforded by inoculation with AMF, decreases with increasing phosphorus (P) supply in the soil. The paradigm suggests that when fertilized with sufficient P, inoculation of crops would not be beneficial. However, the majority of experiments demonstrating the paradigm were conducted in sterile conditions without a background AMF or soil microbial community. Interestingly, intraspecific variation in R. irregularis can greatly alter the yield of cassava even at a full application of the recommended P dose. Cassava is a globally important crop, feeding 800 million people worldwide, and a crop that is highly dependent on AMF for P uptake. In this study, field trials were conducted at three locations in Kenya and Tanzania using different AMF and cassava varieties under different P fertilization levels to test if the paradigm occurs in tropical field conditions. We found that AMF colonization and inoculation responsiveness of cassava does not always decrease with an increased P supply as expected by the paradigm. The obtained results demonstrate that maximizing the inoculation responsiveness of cassava is not necessarily only in conditions of low P availability, but that this is dependent on cassava and fungal genotypes. Thus, the modeling of plant symbiosis with AMF under different P levels in nature should be considered with caution.

Basal cell carcinoma, blue-white variant: Dermatoscopic findings in 32 cases.

BACKGROUND: The diagnosis of basal cell carcinoma is histopathological, but there are dermatoscopic criteria that confer high sensitivity and specificity to help the clinician improve its identification. However, the basal cell carcinoma blue-white variant does not totally meet these dermatoscopic criteria, and thus can be confused with other pigmented tumors. In the literature reviewed, we found only five cases of this variant. AIMS: The present objective is to describe the dermatoscopic characteristics of the blue-white variant of basal cell carcinoma observed in a tertiary dermatology institute. METHODS: The dermatoscopy files of patients with a histopathological diagnosis of basal cell carcinoma between January 1, 2006 and December 31, 2015 were reviewed. RESULTS: A total of 32 cases with blue-white variant of basal cell carcinoma were observed over a period of 10 years. Of these cases, 97% presented dermatoscopic findings not included in the aforementioned criteria, such as whitish septa, structureless white areas, homogenous blue pigmentation and shiny white structures. LIMITATIONS: The small sample size and the retrospective nature of the design. CONCLUSION: We consider it important for dermatologists to know this rare variant of basal cell carcinoma and to familiarize themselves with their dermatoscopic findings, in order to prevent erroneous diagnoses or inadequate treatments.

Macrophage inhibitory factor (MIF) gene polymorphisms are associated with disease susceptibility and with circulating MIF levels in active non-segmental vitiligo in patients from western Mexico.

BACKGROUND: The macrophage migration inhibiting factor (MIF) is a protein that promotes the activation of immune cells and the production of other proinflammatory cytokines such as TNF-α, IL-1ß, and IFN-γ, which have proposed to play an essential role in the pathogenesis of vitiligo. The study aimed to assess the association between MIF polymorphisms (-794 CATT5-8 and -173 G>C), MIF in situ expression, and MIF serum concentrations with susceptibility and disease activity in patients with non-segmental vitiligo (NSV) from western Mexico. METHODS: The study included 111 patients with NSV and 201 control subjects. Genotyping was performed by conventional PCR (-794 CATT5-8 ) and PCR-RFLP (-173 G>C) methods. MIF mRNA expression was quantified by real-time PCR and MIF serum concentrations were determined by ELISA kit. Histopathological samples were analyzed by automated immunohistochemistry. RESULTS: The MIF polymorphisms were associated with NSV susceptibility. Serum concentrations of MIF were higher in patients with active NSV and correlated negatively with the years of evolution. The depigmented skin from patients with active vitiligo showed a high expression of MIF. CONCLUSION: MIF polymorphisms increase the risk of NSV in the western Mexican population. The serum concentrations of MIF and in situ expression are associated with active NSV.

Dermoscopy of non-pigmented eccrine poromas: study of Mexican cases.

BACKGROUND: Eccrine poroma is a benign neoplasm that can mimick a malignant neoplasm dermoscopically. The characteristic vascular pattern of this tumor has not been established. OBJECTIVE: To evaluate dermoscopic features of non-pigmented eccrine poroma in Mexican patients. METHOD: We retrospectively studied histologically proven cases of eccrine poroma from three Mexican hospitals analyzed by four dermoscopists. RESULTS: Thirteen cases were studied. A polymorphous vascular pattern was found in most cases. Four presented with irregular linear and branched vessels with semi-elliptical, or semicircular endings ("chalice-form" and "cherry-blossoms" vessels). Structureless pink-white areas were the most common other dermoscopic finding. CONCLUSIONS: "Chalice-form" and "cherry-blossom" vessels have not been reported in other benign or malignant neoplasms and can be a useful clue to the diagnosis of non-pigmented eccrine poroma. Due to the variability of dermoscopic patterns of eccrine poroma further studies are required to establish the specificity of our findings.