The correct identification of plants is a common necessity not only to researchers but also to the lay public. Recently, computational methods have been employed to facilitate this task, however, there are few studies front of the wide diversity of plants occurring in the world. This study proposes to analyse images obtained from cross-sections of leaf midrib using fractal descriptors. These descriptors are obtained from the fractal dimension of the object computed at a range of scales. In this way, they provide rich information regarding the spatial distribution of the analysed structure and, as a consequence, they measure the multiscale morphology of the object of interest. In Biology, such morphology is of great importance because it is related to evolutionary aspects and is successfully employed to characterize and discriminate among different biological structures. Here, the fractal descriptors are used to identify the species of plants based on the image of their leaves. A large number of samples are examined, being 606 leaf samples of 50 species from Brazilian flora. The results are compared to other imaging methods in the literature and demonstrate that fractal descriptors are precise and reliable in the taxonomic process of plant species identification.

Aldehyde oxidoreductase from Desulfovibrio gigas (DgAOR) is a homodimeric molybdenum-containing protein that catalyzes the hydroxylation of aldehydes to carboxylic acids and contains a Mo-pyranopterin active site and two FeS centers called FeS 1 and FeS 2. The electron transfer reaction inside DgAOR is proposed to be performed through a chemical pathway linking Mo and the two FeS clusters involving the pyranopterin ligand. EPR studies performed on reduced as-prepared DgAOR showed that this pathway is able to transmit very weak exchange interactions between Mo(V) and reduced FeS 1. Similar EPR studies but performed on DgAOR samples inhibited with glycerol and ethylene glycol showed that the value of the exchange coupling constant J increases ~2 times upon alcohol inhibition. Structural studies in these DgAOR samples have demonstrated that the Mo-FeS 1 bridging pathway does not show significant differences, confirming that the changes in J observed upon inhibition cannot be ascribed to structural changes associated neither with pyranopterin and FeS 1 nor with changes in the electronic structure of FeS 1, as its EPR properties remain unchanged. Theoretical calculations indicate that the changes in J detected by EPR are related to changes in the electronic structure of Mo(V) determined by the replacement of the OHx labile ligand for an alcohol molecule. Since the relationship between electron transfer rate and isotropic exchange interaction, the present results suggest that the intraenzyme electron transfer process mediated by the pyranopterin moiety is governed by a Mo ligand-based regulatory mechanism.

The Cys-His bridge as electron transfer conduit in the enzymatic catalysis of nitrite to nitric oxide by nitrite reductase from Sinorhizobium meliloti 2011 (SmNir) was evaluated by site-directed mutagenesis, steady state kinetic studies, UV-vis and EPR spectroscopic measurements as well as computational calculations. The kinetic, structural and spectroscopic properties of the His171Asp (H171D) and Cys172Asp (C172D) SmNir variants were compared with the wild type enzyme. Molecular properties of H171D and C172D indicate that these point mutations have not visible effects on the quaternary structure of SmNir. Both variants are catalytically incompetent using the physiological electron donor pseudoazurin, though C172D presents catalytic activity with the artificial electron donor methyl viologen (k=3.9(4) s) lower than that of wt SmNir (k=240(50) s). QM/MM calculations indicate that the lack of activity of H171D may be ascribed to the NH…OC hydrogen bond that partially shortcuts the T1-T2 bridging Cys-His covalent pathway. The role of the NH…OC hydrogen bond in the pH-dependent catalytic activity of wt SmNir is also analyzed by monitoring the T1 and T2 oxidation states at the end of the catalytic reaction of wt SmNir at pH6 and 10 by UV-vis and EPR spectroscopies. These data provide insight into how changes in Cys-His bridge interrupts the electron transfer between T1 and T2 and how the pH-dependent catalytic activity of the enzyme are related to pH-dependent structural modifications of the T1-T2 bridging chemical pathway.

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Tratamientos intensificados se asocian con neutropenia severa, identificada como factor de riesgo de complicaciones infecciosas en pacientes con enfermedades neoplásicas. Objetivo: Evaluar la importancia del momento de inicio del tratamiento antibiótico en la evolución y pronóstico de pacientes con neutropenia febril (NF) por Cáncer ingresados al Hospital de Niños J.M. de los Ríos entre febrero 2020 – febrero 2022. Métodos: estudio descriptivo, prospectivo, transversal, analítico, se registró formulario de recolección de datos y base de datos Google Drive para análisis estadístico por distribución de frecuencias y porcentajes. Se entregó Consentimiento y Asentimiento Informado a padres y pacientes, ambos aprobados por Comisión de Bioética, capacitándose en manejo de fiebre neutropénica. Incluyó pacientes con fiebre durante la primera hora después de recibir quimioterapia, indicándoseles antibióticos. Resultados: sexo masculino 63,2% (36/57) de los casos de NF y preescolares 43,9% (25/57) fueron los más afectados. Leucemia Linfocítica Aguda fue el cáncer más frecuente 68,4% (39/57) y Bacteriemia 40,4% (23/57) la patología infecciosa predominante. Evolucionaron satisfactoriamente en la mayoría de los casos; la Media de la estancia hospitalaria fue 14,56 días, más prolongada en pacientes con Leucemia Linfocítica Aguda en fase de inducción. Gramnegativos los aislamientos predominantes 35,1 % (20/57), representados por Pseudomonas aeruginosa. El tiempo de cumplimiento de antibióticos fue 4 - 12 horas desde el inicio de fiebre. Mortalidad ocurrió por enfermedad de base mal controlada. Conclusiones: cumplimiento de antibióticos durante la primera hora de fiebre neutropénica en pacientes pediátricos con cáncer disminuye complicaciones infecciosas, estancia hospitalaria y mortalidad.

This work proposes an analytical method to identify plant species based on microscopy images of the midrib cross-section of leaves. Unlike previous shape-based approaches based on the individual shape of external contours and cells, an architectural analysis is proposed, where the midrib is semi-automatically segmented and partitioned into histologically relevant structures composed of layers of cells and vascular structures. Using a sequence of morphological operations, a set of geometrical measures from the cells in each layer is extracted to produce a vector of features for species categorization. The method applied to a database containing 10 species of plants from the Brazilian flora achieved a success rate of 91.7%, outperforming other classical shape-based approaches published in the literature.