Photochemical tyrosine oxidation with a hydrogen-bonded proton acceptor by bidirectional proton-coupled electron transfer

Amino acid radical generation and transport are fundamentally important to numerous essential biological processes to which small molecule models lend valuable mechanistic insights. Pyridyl-amino acid-methyl esters are appended to a rhenium(I) tricarbonyl 1,10-phenanthroline core to yield rhenium–amino acid complexes with tyrosine ([Re]–Y–OH) and phenylalanine ([Re]–F). The emission from the [Re] center is more significantly quenched for [Re]–Y–OH upon addition of base. Time-resolved studies establish that excited-state quenching occurs by a combination of static and dynamic mechanisms. The degree of quenching depends on the strength of the base, consistent with a proton-coupled electron transfer (PCET) quenching mechanism. Comparative studies of [Re]–Y–OH and [Re]–F enable a detailed mechanistic analysis of a bidirectional PCET process.National Institutes of Health (U.S.) (GM47274

Photoinitiated proton-coupled electron transfer and radical transport kinetics in class la ribonucleotide reductase

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.Cataloged from PDF version of thesis. Vita.Includes bibliographical references.Proton-coupled electron transfer (PCET) is a critical mechanism in biology, underpinning key processes such as radical transport, energy transduction, and enzymatic substrate activation. Ribonucleotide reductases (RNRs) rely on PCET to mediate the rate-limiting step in the synthesis of DNA precursors. E. coli class Ia RNR consists of two dimeric subunits: [alpha]₂ contains the active site, while [beta]₂ contains a stable diferric-tyrosyl radical cofactor. During turnover, transport occurs over 35 Ȧ, from Y₁₂₂ in [beta]₂ to C₄₃₉ in [alpha]₂) where an active-site thiyl radical mediates turnover. Radical transport is proposed to occur over a series of highly conserved redox-active amino acids, including Y₃₅₆ in [beta]₂,and Y₇₃₁ and Y₇₃₀ in [alpha]₂ . This thesis examines three subject areas of PCET that pertain to RNR: Small-molecule model systems provide insights into tyrosine oxidation and radical generation. Under physiological conditions, tyrosine oxidation is accompanied by deprotonation and occurs by PCET. A critical factor in PCET reactions is the nature ofthe proton acceptor and the presence ofhydrogen bonding. In a modular model system, pyridyl-amino acid-methyl esters are appended to rhenium(I) tricarbonyl phenanthroline to yield rhenium-amino acid complexes. In dichloromethane solution, bases coordinate to tyrosine by hydrogen bonding. Emission kinetics reveal base-dependent oxidation by PCET. A photopeptide composed of the 19 C-terminal residues of [beta]₂, fluorinated tyrosine in place of Y₃₅₆, and a rhenium(I) bipyridine photooxidant enables photoinitated radical transport into [alpha]₂. Transient absorption kinetics show rapid radical transport (10⁵ s-¹) that is only observed when both Y₇₃₁ and Y₇₃₀, are present, suggesting a critical role for the Y₇₃₁-Y₇₃₀, dyad for radical transport in RNR. An intact, photochemical [beta]₂ enables studies of an [alpha]₂:[beta]₂ complex. A bromomethylpyridine rhenium(I) phenanthroline photooxidant labels a single surface-cysteine mutant of [beta]₂ at position 355 to yield [Re]- [beta]₂. Under flash-quench conditions, transient absorption reveals a tyrosine radical. [Re] -[beta]₂ binds [alpha]₂ and is capable of light-initiated substrate turnover. Transient emission quenching experiments reveal Y₃₅₆ oxidation that is dependent on the presence of Y₇₃₁ in [alpha]₂. This result suggests that a Y₃₅₆-Y₇₃₁-Y₇₃₀ triad mediates radical transport across the subunit interface and into [alpha]₂.by Arturo A. Pizano.Ph.D

Application of the Trajectory Sensitivity Theory to Small Signal Stability Analysis

The security assessment of power systems represents one of the principal studies that must be carried out in energy control centers. In this context, small-signal stability analysis is very important to determine the corresponding control strategies to improve security under stressed operating conditions of power systems. This chapter details a practical approach for assessing the stability of power system’s equilibrium points in real time based on the concept of trajectory sensitivity theory. This approach provides complementary information to that given by selective modal analysis: it determines how the state variables linked with the critical eigenvalues are affected by the system’s parameters and also determines the way of judging how the system’s parameters affect the oscillatory behavior of a power system. The WSCC 9-bus and a 190-buses equivalent system of the Mexican power system are used to demonstrate the generality of the approach as well as how its application in energy management systems is suitable for power system operation and control

Histidine-tryptophan-ketoglutarate solution versus blood cardioplegia in cardiac surgery: A propensity-score matched analysis

Background: Choosing a cardioplegic solution is a significant issue in modern cardiac surgery. Although different options are available, the optimal strategy for myocardial protection has not been established. The aim of this study was to compare intraoperative and postoperative effects of histidine–tryptophan–ketoglutarate (HTK) solution with those of standard blood cardioplegia with St Thomas No 2 solution. The study was conducted using a large cohort of adult patients undergoing complex cardiac surgery. Methods: This study was a single center retrospective review of prospectively collected data. Between January 2008 and December 2015, 4480 patients underwent cardiac surgery using cardiopulmonary bypass (CPB) and cardioplegic arrest. Patients were divided into a blood cardioplegia group (n = 3852) and an HTK solution group (n = 628). Propensity score matching was used to adjust for differences between the two groups, and 292 matched pairs were identified. The primary end point was Intensive Care Unit (ICU) length of stay (LOS). Secondary end points included intraoperative changes in serum sodium concentration, readmission to ICU, transfusion of blood products, 30-day hospital readmission, 30-day mortality, and the incidence of major postoperative complications. Results: No significant differences were found between the matched groups with regard to baseline characteristics. Aortic cross-clamp and CPB times were longer for the blood cardioplegia (147.4 versus 132.8 min; P less than .001). Administration of HTK solution was associated with acute and transient hyponatremia (141 versus 130 mmol/L; P less than .001). ICU LOS was comparable between the groups (5.4 versus 5.4 days; P = .585). No significant differences were noted in any other secondary end point. Conclusions: During complex cardiac surgery, both cardioplegia techniques were equivalent in terms of early clinical outcomes. © 2018 Forum Multimedia Publishing, LLC

Isolated, neglected, and likely threatened: a new species of Magoniella (Polygonaceae) from the seasonally dry tropical forests of Northern Colombia and Venezuela revealed from nuclear, plastid, and morphological data

Seasonally tropical dry forests (SDTFs) in the American tropics are a highly diverse yet poorly understood and endangered ecosystem scattered from Northern Mexico to Southern Argentina. One floristic element of the STDFs is the genus Magoniella (Polygonaceae), which includes two liana species, M. laurifolia and M. obidensis, which have winged fruits and are distributed from Costa Rica to Southern Brazil. In a field expedition to the SDTFs of the Colombian Caribbean in 2015, morphologically distinctive individuals of Magoniella were found. In this study, we investigated the species boundaries within Magoniella and determined the phylogenetic position of these morphologically distinctive individuals in the tribe Triplaridae. We compiled morphological trait data across 19 specimens of both species and produced newly sequenced nuclear–plastid DNA data for M. obidensis. Morphometric analyses revealed significant differences in fruit length and perianth size among individuals from the Colombian Caribbean compared to M. obidensis and bract length when compared to M. laurifolia. Maximum likelihood analysis of non-conflicting nuclear and plastid datasets placed the Colombian Caribbean individuals as sister to M. obidensis with maximum statistical support. Additionally, pairwise sequence comparisons of the nuclear ribosomal ITS and the lfy2i loci consistently showed 15-point mutations (10 transitions, five transversions) and six 2 bp-long substitutions that differ between M. obidensis and the Colombian Caribbean individuals. Our morphological and molecular evidence thus suggests that the Colombian Caribbean individuals of Magoniella represent a divergent population from M. laurifolia and M. obidensis, which we describe and illustrate as a new species, M. chersina. Additionally, we provide nomenclatural updates for M. laurifolia and M. obidensis. This study highlights the power of combining morphological and molecular evidence in documenting and naming plant diversity

Simulación y revisión de un dispositivo de pequeña escala para la conversión de energía del oleaje

En este trabajo de investigación se aborda la exploración y el análisis del potencial energético undimotriz en la costa mexicana a través del análisis y la simulación electromagnética del dispositivo transductor, para la conversión de energía del oleaje en electricidad; un dispositivo que se desarrolló para este propósito es el generador eléctrico lineal (GEL) de imanes permanentes. El potencial energético del oleaje, obtenido en un trabajo preliminar, en diversos puntos en aguas costeras mexicanas, proporciona un panorama precedente para el diseño de estos dispositivos. La utilización de generadores eléctricos lineales para conseguir energía eléctrica por fuentes alternas es una temática que cada vez toma mayor fuerza para el progreso de nuevos sistemas de generación distribuida (microrredes), por lo que este trabajo, además de determinar el potencial energético a través de la simulación electromagnética del dispositivo, analiza el rendimiento y calidad energética proporcionada por GEL. El análisis de simulación desarrollado en este trabajo se fundamenta con base en la obtención del espectro de desplazamiento, en función de la altura significativa de las olas y su periodicidad en los puntos costeros mexicanos analizados en el trabajo preliminar. Además, se contribuye al diseño y desarrollo de dispositivos enfocados a la microgeneración por undimotriz, lo que abre el abanico de posibilidades para el modelado y desarrollo de convertidores de electrónica de potencia, para ayudar al control y la calidad energética de estos dispositivos generadores eléctricos lineales

Analysis of Optimal Steady-State Operation of Power Systems with Embedded FACTS Devices: A Matlab-Based Flexible Approach

This book chapter presents a flexible approach to incorporate mathematical models of FACTS devices into the Power Flow (PF) and the Optimal Power Flow (OPF) analysis tools, as well as into the standard OPF Market-Clearing (OPF-MC) procedure. The proposed approach uses the Matlab Optimization Toolbox because it allows to easily: (a) implement a given optimization model, (b) include different objective functions using distinct equality and inequality constraints and (c) modify and reuse an optimization model that has been previously implemented. The conventional OPF model is the main core of the proposed approach, which is easily implemented and adapted to include the mathematical models of FACTS devices. The resulting implementation of the OPF model featuring FACTS devices can be easily modified and adjusted to obtain the implementation of both the PF and the OPF-MC models which includes such devices. It should be mentioned that with the flexible approach proposed here, the complexity as well as the implementation time of optimized models featuring embedded FACTS devices is significantly reduced, since it is not necessary to define the expressions associated with the hessian matrix and the gradient vector. The flexibility and reliability of the proposed approach are demonstrated by means of several study cases using test as well as real power systems

Inflammaging as a link between autoimmunity and cardiovascular disease: The case of rheumatoid arthritis

Currently, traditional and non-traditional risk factors for cardiovascular disease have been established. The first group includes age, which constitutes one of the most important factors in the development of chronic diseases. The second group includes inflammation, the pathophysiology of which contributes to an accelerated process of vascular remodelling and atherogenesis in autoimmune diseases. Indeed, the term inflammaging has been used to refer to the inflammatory origin of ageing, explicitly due to the chronic inflammatory process associated with age (in healthy individuals). Taking this into account, it can be inferred that people with autoimmune diseases are likely to have an early acceleration of vascular ageing (vascular stiffness) as evidenced in the alteration of non-invasive cardiovascular tests such as pulse wave velocity. Thus, an association is created between autoimmunity and high morbidity and mortality rates caused by cardiovascular disease in this population group. The beneficial impact of the treatments for rheumatoid arthritis at the cardiovascular level has been reported, opening new opportunities for pharmacotherapy

Allergen sensitization linked to climate and age, not to intermittent-persistent rhinitis in a cross-sectional cohort study in the (sub)tropics

Background: Allergen exposure leads to allergen sensitization in susceptible individuals and this might influence allergic rhinitis (AR) phenotype expression. We investigated whether sensitization patterns vary in a country with subtropical and tropical regions and if sensitization patterns relate to AR phenotypes or age. Methods: In a national, cross-sectional study AR patients (2-70 y) seen by allergists underwent blinded skin prick testing with a panel of 18 allergens and completed a validated questionnaire on AR phenotypes. Results: 628 patients were recruited. The major sensitizing allergen was house dust mite (HDM) (56%), followed by Bermuda grass (26%), ash (24%), oak (23%) and mesquite (21%) pollen, cat (22%) and cockroach (21%). Patients living in the tropical region were almost exclusively sensitized to HDM (87%). In the central agricultural zones sensitization is primarily to grass and tree pollen. Nationwide, most study subjects had perennial (82.2%), intermittent (56.5%) and moderate-severe (84.7%) AR. Sensitization was not related to the intermittent-persistent AR classification or to AR severity; seasonal AR was associated with tree (p < 0.05) and grass pollen sensitization (p < 0.01). HDM sensitization was more frequent in children (0-11 y) and adolescents (12-17 y) (subtropical region: p < 0.0005; tropical region p < 0.05), but pollen sensitization becomes more important in the adult patients visiting allergists (Adults vs children + adolescents for tree pollen: p < 0.0001, weeds: p < 0.0005). Conclusions: In a country with (sub)tropical climate zones SPT sensitization patterns varied according to climatological zones; they were different from those found in Europe, HDM sensitization far outweighing pollen allergies and Bermuda grass and Ash pollen being the main grass and tree allergens, respectively. Pollen sensitization was related to SAR, but no relation between sensitization and intermittent-persistent AR or AR severity could be detected. Sensitization patterns vary with age (child HDM, adult pollen). Clinical implications of our findings are dual: only a few allergens –some region specific- cover the majority of sensitizations in (sub)tropical climate zones. This is of major importance for allergen manufacturers and immunotherapy planning. Secondly, patient selection in clinical trials should be based on the intermittent-persistent and severity classifications, rather than on the seasonal-perennial AR subtypes, especially when conducted in (sub)tropical countries

Expediciones Humboldt: Honda-Méndez, Tolima

Este informe presenta los resultados de la caracterización biológica de uno de los bosques secos con mejor estado de conservación en el departamento del Tolima, ubicado entre los municipio de Honda, Méndez y Armero-Guayabal. Estos bosques se encuentran en una matriz de ganadería y producción agropecuaria, donde las coberturas boscosas son conservadas por los propietarios, conscientes de la importancia de este ecosistema para la provisión de bienes y servicios ecosistémicos. Esperamos que esta información producto de la capacidad científica del Instituto Humboldt, sea relevante y útil en las decisiones de planificación estratégica tanto en el ordenamiento territorial de los municipios de Honda, Méndez y Armero-Guayabal, como para las decisiones de conservación que se tomen en la regiónBogotáCiencias Básicas de la Biodiversida