l-Isoleucine-Schiff Base Copper(II) Coordination Polymers: Crystal Structure, Spectroscopic, Hirshfeld Surface, and DFT Analyses.

A new copper(II) coordination polymer was synthesized from the l-isoleucine-Schiff base and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, single-crystal X-ray diffraction (XRD) analysis, electronic paramagnetic resonance, and thermogravimetric analysis. XRD analysis confirmed the square planar coordination geometry of metallic centers and a zipper-like polymer structure. Vibrational, electronic, and paramagnetic spectroscopies and thermal analysis were consistent with the crystal structure. A Hirshfeld surface (HS) and density functional theory (DFT) analyses were employed to gain additional insight into interactions responsible for complex packing. The quantitative examination of two-dimensional (2D) fingerprint plots revealed, among other van der Waals forces, the dominating participation of H···H and H···Cl interactions in the molecular packing. The use of computational methods provided great help in detailing the supramolecular interactions occurring in the crystal, which were mainly van der Waals attractions. The electronic transition analysis helped corroborate the electronic transitions observed experimentally in the absorption spectrum. The frequency and vibrational mode analysis gave a deeper insight into the characterization of the CuLCL complex.

A Machine Learning Approach for Modelling Cold-Rolling Curves for Various Stainless Steels.

Stainless steel is a cold-work-hardened material. The degree and mechanism of hardening depend on the grade and family of the steel. This characteristic has a direct effect on the mechanical behaviour of stainless steel when it is cold-formed. Since cold rolling is one of the most widespread processes for manufacturing flat stainless steel products, the prediction of their strain-hardening mechanical properties is of great importance to materials engineering. This work uses artificial neural networks (ANNs) to forecast the mechanical properties of the stainless steel as a function of the chemical composition and the applied cold thickness reduction. Multiple linear regression (MLR) is also used as a benchmark model. To achieve this, both traditional and new-generation austenitic, ferritic, and duplex stainless steel sheets are cold-rolled at a laboratory scale with different thickness reductions after the industrial intermediate annealing stage. Subsequently, the mechanical properties of the cold-rolled sheets are determined by tensile tests, and the experimental cold-rolling curves are drawn based on those results. A database is created from these curves to generate a model applying machine learning techniques to predict the values of the tensile strength (Rm), yield strength (Rp), hardness (H), and elongation (A) based on the chemical composition and the applied cold thickness reduction. These models can be used as supporting tools for designing and developing new stainless steel grades and/or adjusting cold-forming processes.

[Use of current imaging tools for the study of odontogenic myxoma. A review of the literature]. / Uso de herramientas de imagenología actual para el estudio del mixoma odontogénico. Una revisión de la literatura.

Odontogenic myxoma (OM) is currently classified as a benign tumor of ectomesenchymal origin, observed between the second and fourth decade of age, with a predilection in women and predominance in the mandibular region, composed of rounded and angular cells embedded in an abundant myxoid stroma, of aggressive biological behavior, having the characteristic of being locally infiltrative. Tumor cells spread in the intratrabecular space beyond the bone limit, making it difficult to determine the edge of the tumor, even without cortical continuity, presenting intermittent direct contact with soft tissue; the appearance can be unilocular (small lesions), or commonly the typical image is that of a destructive lesion with poorly defined borders with a multilocular growth pattern, for which the use of advanced medical images such as Cone Beam Computed Tomography (CTHC), Computed Tomography (CT), Magnetic Resonance Imaging (MRI), are useful to establish an adequate diagnosis with the ability to point out the characteristics of OM with precision and three-dimensional perspective. This review presents a systematic analysis of the types of imaging tools currently used for the study of OM.

A Novel Glutathione S-Transferase Gtt2 Class (VpGSTT2) Is Found in the Genome of the AHPND/EMS Vibrio parahaemolyticus Shrimp Pathogen.

Glutathione S-transferases are a family of detoxifying enzymes that catalyze the conjugation of reduced glutathione (GSH) with different xenobiotic compounds using either Ser, Tyr, or Cys as a primary catalytic residue. We identified a novel GST in the genome of the shrimp pathogen V. parahaemolyticus FIM- S1708+, a bacterial strain associated with Acute Hepatopancreatic Necrosis Disease (AHPND)/Early Mortality Syndrome (EMS) in cultured shrimp. This new GST class was named Gtt2. It has an atypical catalytic mechanism in which a water molecule instead of Ser, Tyr, or Cys activates the sulfhydryl group of GSH. The biochemical properties of Gtt2 from Vibrio parahaemolyticus (VpGSTT2) were characterized using kinetic and crystallographic methods. Recombinant VpGSTT2 was enzymatically active using GSH and CDNB as substrates, with a specific activity of 5.7 units/mg. Low affinity for substrates was demonstrated using both Michaelis-Menten kinetics and isothermal titration calorimetry. The crystal structure showed a canonical two-domain structure comprising a glutathione binding G-domain and a hydrophobic ligand H domain. A water molecule was hydrogen-bonded to residues Thr9 and Ser 11, as reported for the yeast Gtt2, suggesting a primary role in the reaction. Molecular docking showed that GSH could bind at the G-site in the vicinity of Ser11. G-site mutationsT9A and S11A were analyzed. S11A retained 30% activity, while T9A/S11A showed no detectable activity. VpGSTT2 was the first bacterial Gtt2 characterized, in which residues Ser11 and Thr9 coordinated a water molecule as part of a catalytic mechanism that was characteristic of yeast GTT2. The GTT2 family has been shown to provide protection against metal toxicity; in some cases, excess heavy metals appear in shrimp ponds presenting AHPND/EMS. Further studies may address whether GTT2 in V. parahaemolyticus pathogenic strains may provide a competitive advantage as a novel detoxification mechanism.

Dropout, Autonomy and Reintegration in Spain: A Study of the Life of Young Women on Temporary Release.

This study analyses the psycho-educational and social paths of women prisoners after the time they drop out of school as minors, based on different variables related to autonomy and their preparedness to face temporary release. METHODS: Qualitative and quantitative methods were used to analyse a national sample of 310 women prisoners (30.1% of the population) in 31 prisons through a mixed-mode questionnaire and interview. We analysed the significant association of variables related to dropout and obtained a log-linear model that relates dropout to recidivism and Roma culture. Work experience was analysed using the McNemar test, and variables influencing the participant's job at the time of the study were analysed by applying cluster analysis. RESULTS: Young women comprise 66.6% of individuals who drop of the education system as minors (primary 49.3% and secondary 22%). They drop out between the ages of 7 and 17, and have traits of greater vulnerability than those who stayed in school until adulthood. In this population, we find a significant association with various factors: belonging to Roma culture, having family members in prison and delinquent recidivism; and higher unemployment (43.4%) and low income before entering prison. This situation is increasing today. In prison, these women had more connection to education/training, which can improve their employability. They also encounter difficulties with personal security, decision-making, personal/professional dependence, planning for the future, administrative matters and handling information and communication technologies, job-seeking skills, etc. Their self-perceived strengths are, however, assuming responsibility, taking orders, respecting schedules and timetables, working on a team and feeling prepared to start a job, as well as having optimistic convictions about the future. CONCLUSION: The vulnerabilities and risk factors studied have a negative influence primarily on processes of personal, social and job autonomy in female minors who left the education system. Yet these minors show factors of protection and resilience. On temporary release at the time of the study, they face the consequences that their prison terms and incarceration have for their perceptions, attitudes, competencies and future prospects, as well as social marginalization and stigma. Early, coherent socio-educational interventions are thus needed to improve social integration-reintegration.

Immune response of human cultured cells towards macrocyclic Fe2PO and Fe2PC bioactive cyclophane complexes.

Synthetic molecules that mimic the function of natural enzymes or molecules have untapped potential for use in the next generation of drugs. Cyclic compounds that contain aromatic rings are macrocyclic cyclophanes, and when they coordinate iron ions are of particular interest due to their antioxidant and biomimetic properties. However, little is known about the molecular responses at the cellular level. This study aims to evaluate the changes in immune gene expression in human cells exposed to the cyclophanes Fe2PO and Fe2PC. Confluent human embryonic kidney cells were exposed to either the cyclophane Fe2PO or Fe2PC before extraction of RNA. The expression of a panel of innate and adaptive immune genes was analyzed by quantitative real-time PCR. Evidence was found for an inflammatory response elicited by the cyclophane exposures. After 8 h of exposure, the cells increased the relative expression of inflammatory mediators such as interleukin 1; IRAK, which transduces signals between interleukin 1 receptors and the NFκB pathway; and the LPS pattern recognition receptor CD14. After 24 h of exposure, regulatory genes begin to counter the inflammation, as some genes involved in oxidative stress, apoptosis and non-inflammatory immune responses come into play. Both Fe2PO and Fe2PC induced similar immunogenetic changes in transcription profiles, but equal molar doses of Fe2PC resulted in more robust responses. These data suggest that further work in whole animal models may provide more insights into the extent of systemic physiological changes induced by these cyclophanes.

Comparative Studies of Structures and Peroxidase-like Activities of Copper(II) and Iron(III) Complexes with an EDTA-Based Phenylene-Macrocycle and Its Acyclic Analogue.

With the objective of studying the conformational and macrocyclic effects of selected metal chelates on their peroxidase activities, Cu2+ and Fe3+ complexes were synthesized with a macrocyclic derivative of ethylenediaminetetraacetic acid and o-phenylenediamine (abbreviated as edtaodH2) and its new open-chain analogue (edtabzH2). The Fe3+ complex of edtaodH2 has a peroxidase-like activity, whereas the complex of edtabzH2 does not. The X-ray study of the former shows the formation of a dimeric molecule {[Fe(edtaod)]2O} in which each metal with an octahedral coordination is overposed over the macrocyclic cavity, as a result of rigid macrocyclic frame, to form an Fe-O-Fe bridge; the exposure of the central metal to the environment facilitates the capture of oxygen to drive the biomimetic activity. The peroxidase-inactive Fe3+ complex consists of a mononuclear complex ion [Fe(edtabz)(H2O)]+, the metal ion of which is suited in a distorted pentagonal bipyramid to be protected from environmental oxygen. The copper(II) complexes, which have mononuclear structures with high thermodynamic stability compared with the iron(III) complexes, show no peroxidase activity. The steric effects play a fundamental role in the biomimetic activity.

Tratamientos para niños y adolescentes con trastorno por déficit de atención/hiperactividad: ¿cuál es la base de la evidencia hasta ahora? / Treatments for children and adolescents with attention deficit hyperactivity disorder: what is the evidence base to date?

La evidencia obtenida a partir de estudios empíricos constituye un elemento clave que, junto con la preferencia del paciente y la consideración de su estado clínico y circunstancias particulares, debería tenerse en cuenta en el proceso de toma de decisiones clínicas. Este artículo proporciona una visión global de la evidencia actual en relación con el tratamiento del trastorno por déficit de atención/hiperactividad (TDAH), y expone los resultados de los más recientes metaanálisis de ensayos controlados aleatorizados que evalúan los tratamientos farmacológicos y no farmacológicos. En general, los recientes metaanálisis disponibles muestran que los psicoestimulantes, y en menor medida los no psicoestimulantes, son eficaces en términos de control de los síntomas nucleares del TDAH, al menos a corto plazo, y que la eficacia para tratar los síntomas nucleares del TDAH de los tratamientos no farmacológicos (programas comportamentales, dietas, entrenamientos cognitivos y neurofeedback) continúa siendo dudosa, aunque algunas intervenciones terapéuticas no farmacológicas son eficaces para resolver problemas asociados al trastorno, como las intervenciones conductuales para las conductas oposicionistas y las habilidades parentales, y el entrenamiento cognitivo para los déficits en la memoria de trabajo. No obstante, la mayoría de los ensayos controlados aleatorizados son ensayos de eficacia a corto plazo con muestras de pacientes reclutadas en poblaciones seleccionadas y, como tal, no son completamente ilustrativos para la práctica clínica diaria. Con el fin de establecer una conexión entre la evidencia teórica y la práctica clínica diaria, tenemos ensayos clínicos comparativos, ensayos pragmáticos, ensayos retirada-placebo, metaanálisis en red y metaanálisis con datos del paciente individual (AU)

The evidence base from empirical studies is one of the elements, along with patients’ preference and consideration of particular clinical state and circumstances, that should be taken into account in the process of clinical decision making. This paper provides an overview of the current evidence base for the treatment of attention-deficithyperactivity disorder (ADHD), drawing on the results of the most recent meta-analyses of randomized controlled trials assessing the pharmacological and non-pharmacological treatment of ADHD. Overall, available recent meta-analyses show that psychostimulants, and, although to a less extent, non psychostimulants, are efficacious in terms of control of core ADHD symptoms, at least in the short term; and although the efficacy of non-pharmacological treatments (behavioral interventions, diet, cognitive training and neurofeedback) for ADHD core symptoms remains uncertain, some nonpharmacological approach are efficacious for ADHD-related problems, such as behavioral interventions for oppositional problems and parenting skills, and cognitive training for working memory deficits. However, most of the available randomized controlled trials are short-term efficacy trials recruiting selected populations of patients and, as such, they are not fully informative for the daily clinical practice. Head-to-head trials, pragmatic trials, placebo-withdrawal trials, network meta-analyses and individual patient data meta-analyses are encouraged in the field to bridge the gap between theoretical evidence and daily clinical practice (AU)

Poder de discriminación del funcionamiento ejecutivo y de la teoría de la mente en el trastorno por déficit de atención/hiperactividad. Fundamentos para la intervención / Discriminatory power of executive functions and of theory of mind in attention deficit hyperactivity disorder. Rationale for intervention

Introducción. Los déficits en funcionamiento ejecutivo y en teoría de la mente (ToM) están presentes en los niños con trastorno por déficit de atención/hiperactividad (TDAH). Identificar la magnitud de la asociación entre funcionamiento ejecutivo y ToM resulta primordial para la comprensión del trastorno. Objetivos. Adoptando un enfoque de evaluación naturalista, se analiza la capacidad del funcionamiento ejecutivo frente a la ToM para discriminar entre niños con TDAH y con desarrollo típico, y se identifica el grado de asociación entre déficits en los componentes de funcionamiento ejecutivo (regulación conductual y metacognitivos) y de la ToM. Sujetos y métodos. Participaron un grupo de 35 niños con TDAH y otro de 37 niños con desarrollo típico entre 7 y 11 años, igualados en edad y capacidad intelectual. Los padres evaluaron las habilidades de ToM y los profesores estimaron las funciones ejecutivas. Resultados y conclusiones. El porcentaje de niños con TDAH clasificados correctamente fue superior en el análisis discriminante al introducir los componentes de funcionamiento ejecutivo como variable independiente, que en el análisis discriminante realizado con la ToM. No obstante, un elevado porcentaje de niños con déficits en funcionamiento ejecutivo también tenían problemas en ToM. Se revisan intervenciones enfocadas en el desarrollo de un rango amplio de procesos ejecutivos (AU)

Introduction. Executive functions and theory of mind (ToM) deficits are present in children with attention deficit hyperactivity disorder (ADHD). Identifying the magnitude of the association between executive functions and ToM is important for understanding the disorder. Aims. This study adopts a naturalistic evaluation approach to analyze the executive functions versus ToM ability to discriminate between children with ADHD and typically developing children and to identify the degree of association between deficits in the components of executive functions (behavioral regulation and metacognitive) and ToM. Subjects and methods. Thirty-five children with ADHD and 37 typically developing children-7 to 11 years old, matched in age and intelligence quotient, participated in this study. Parents assessed ToM skills and teachers estimated the executive functions. Results and conclusions. The percentage of children with ADHD classified correctly was higher in the discriminant analysis where the executive functions components were introduced as an independent variable than in the discriminant analysis performed with the ToM. However, a high percentage of children with executive functions deficits had also problems in ToM. Interventions focused on the development of a broad range of executive processes are reviewed (AU)

Arginine kinase shows nucleoside diphosphate kinase-like activity toward deoxythymidine diphosphate.

Arginine kinase (AK) (ATP: L-arginine phosphotransferase, E.C. 2.7.3.3) catalyzes the reversible transfer of ATP γ-phosphate group to L-arginine to synthetize phospho-arginine as a high-energy storage. Previous studies suggest additional roles for AK in cellular processes. Since AK is found only in invertebrates and it is homologous to creatine kinase from vertebrates, the objective of this work was to demonstrate nucleoside diphosphate kinase-like activity for shrimp AK. For this, AK from marine shrimp Litopenaeus vannamei (LvAK) was purified and its activity was assayed for phosphorylation of TDP using ATP as phosphate donor. Moreover, by using high-pressure liquid chromatography (HPLC) the phosphate transfer reaction was followed. Also, LvAK tryptophan fluorescence emission changes were detected by dTDP titration, suggesting that the hydrophobic environment of Trp 221, which is located in the top of the active site, is perturbed upon dTDP binding. The kinetic constants for both substrates Arg and dTDP were calculated by isothermal titration calorimetry (ITC). Besides, docking calculations suggested that dTDP could bind LvAK in the same cavity where ATP bind, and LvAK basic residues (Arg124, 126 and 309) stabilize the dTDP phosphate groups and the pyrimidine base interact with His284 and Ser122. These results suggest that LvAK bind and phosphorylate dTDP being ATP the phosphate donor, thus describing a novel alternate nucleoside diphosphate kinase-like activity for this enzyme.

[Comorbidity of autism spectrum disorder and attention deficit with hyperactivity. A review study]. / Comorbilidad del trastorno del espectro autista y el déficit de atención con hiperactividad. Estudio de revisión.

INTRODUCTION: The high presence of attention deficit hyperactivity disorder (ADHD) in autism spectrum disorder (ASD) has been acknowledged in the Diagnostic and statistical manual of mental disorders, fifth edition, thus allowing the diagnosis of both disorders. AIMS: The purpose of this study is to review the research published between 2010 and 2014 on the cognitive and social characteristics of the concurrence of ASD and ADHD. DEVELOPMENT: A review of the 33 studies that were identified showed evidence that the prevalence of symptoms of ADHD in children with ASD was 33-37%. The comorbid condition presents a greater deficit in inhibitory control, attention and working memory. Likewise, in social cognition, the clinical features of ADHD increase the difficulties in cases of ASD. Moreover, the clinical profile of ASD + ADHD is seen to be more severe than that of pure ADHD or ASD, and delayed language development and the intensity/frequency of tantrums are symptoms that are a valuable aid in identification at early ages. CONCLUSIONS: Findings suggest an 'additive' overlapping and ASD + ADHD shares some of the deficits from both disorders, which has implications for the evaluation and design of effective treatments.

TITLE: Comorbilidad del trastorno del espectro autista y el deficit de atencion con hiperactividad. Estudio de revision.Introduccion. La elevada presencia de trastorno por deficit de atencion/hiperactividad (TDAH) en el trastorno del espectro autista (TEA) ha sido reconocida en el Manual diagnostico y estadistico de los trastornos mentales, quinta edicion, permitiendo el diagnostico de ambos trastornos. Objetivo. Revisar las investigaciones publicadas entre 2010 y 2014 sobre las caracteristicas cognitivas y sociales de la coocurrencia del TEA y el TDAH. Desarrollo. La revision de los 33 estudios identificados evidencia una prevalencia de sintomas de TDAH en niños con TEA del 33-37%. La condicion comorbida presenta mas deficit en el control inhibitorio, la atencion y la memoria de trabajo. Asimismo, en cognicion social, la sintomatologia del TDAH incrementa las dificultades en los casos de TEA. Ademas, el perfil clinico de TEA + TDAH muestra mayor gravedad que el de TDAH o TEA puros, y el retraso en el lenguaje y la intensidad/frecuencia de rabietas son sintomas que ayudan a la identificacion en edades tempranas. Conclusiones. Los hallazgos sugieren una superposicion 'aditiva', y el TEA + TDAH comparte algunos deficits de ambos trastornos, lo cual tiene implicaciones para la evaluacion y el diseño de tratamientos efectivos.

Comorbilidad del trastorno del espectro autista y el déficit de atención con hiperactividad. Estudio de revisión / omorbidity of autism spectrum disorder and attention deficit with hyperactivity. A review study

Introducción. La elevada presencia de trastorno por déficit de atención/hiperactividad (TDAH) en el trastorno del espectro autista (TEA) ha sido reconocida en el Manual diagnóstico y estadístico de los trastornos mentales, quinta edición, permitiendo el diagnóstico de ambos trastornos. Objetivo. Revisar las investigaciones publicadas entre 2010 y 2014 sobre las características cognitivas y sociales de la coocurrencia del TEA y el TDAH. Desarrollo. La revisión de los 33 estudios identificados evidencia una prevalencia de síntomas de TDAH en niños con TEA del 33-37%. La condición comórbida presenta más déficit en el control inhibitorio, la atención y la memoria de trabajo. Asimismo, en cognición social, la sintomatología del TDAH incrementa las dificultades en los casos de TEA. Además, el perfil clínico de TEA + TDAH muestra mayor gravedad que el de TDAH o TEA puros, y el retraso en el lenguaje y la intensidad/ frecuencia de rabietas son síntomas que ayudan a la identificación en edades tempranas. Conclusiones. Los hallazgos sugieren una superposición ‘aditiva’, y el TEA + TDAH comparte algunos déficits de ambos trastornos, lo cual tiene implicaciones para la evaluación y el diseño de tratamientos efectivos (AU)

Introduction. The high presence of attention deficit hyperactivity disorder (ADHD) in autism spectrum disorder (ASD) has been acknowledged in the Diagnostic and statistical manual of mental disorders, fifth edition, thus allowing the diagnosis of both disorders. Aims. The purpose of this study is to review the research published between 2010 and 2014 on the cognitive and social characteristics of the concurrence of ASD and ADHD. Development. A review of the 33 studies that were identified showed evidence that the prevalence of symptoms of ADHD in children with ASD was 33-37%. The comorbid condition presents a greater deficit in inhibitory control, attention and working memory. Likewise, in social cognition, the clinical features of ADHD increase the difficulties in cases of ASD. Moreover, the clinical profile of ASD + ADHD is seen to be more severe than that of pure ADHD or ASD, and delayed language development and the intensity/frequency of tantrums are symptoms that are a valuable aid in identification at early ages. Conclusions. Findings suggest an ‘additive’ overlapping and ASD + ADHD shares some of the deficits from both disorders, which has implications for the evaluation and design of effective treatments (AU)

Úlcera en lengua causada por remanentes radiculares: Reporte de caso / A tongue ulcer caused by radicular remanents: Case report

Un problema frecuente de las personas que se atienden en el primer nivel de atención son las lesiones orales, por lo que los médicos en general y en particular los de atención primaria, deben estar capacitados en reconocerlas. Muchas causas pueden dar como resultado una úlcera en la mucosa oral, por lo que el diagnóstico diferencial puede ser difícil. Se presenta el caso de una mujer de 47 años, que acudió a un centro de atención primaria por presentar una lesión ulcerosa localizada en la parte inferior de la lengua, que resultó ser secundario a un problema dental. (AU)

A common medical problem that primary care physicians encounter in daily practice are oral lesions, for which proper training to identify the possible causes is necessary. Many potential etiologies may cause an oral ulcer, making the differential diagnosis difficult. We present the case of a 47 year-old woman who presented at a primary care center with an ulcer located in the inferior part of the tongue that resulted from a dental problem. (AU)

Habilidades cognitivas, contexto rural y urbano: comparación de perfiles WAIS-IV en jóvenes / Cognitive skills, rural and urban context: comparison of WAIS-IV profiles in youth

La reciente estandarización en Chile de la Escala Wechsler de Inteligencia para Adultos (WAIS), en su cuarta versión, obliga a investigar el impacto que condiciones culturales y ambientales pueden tener sobre el rendimiento intelectual de las personas. El presente estudio comparó el desempeño de jóvenes provenientes de sectores rurales y urbanos de la región del Biobío, segmentados según nivel educativo de los padres como variable de aproximación al nivel socioeconómico. Los resultados muestran un efecto de interacción entre el nivel socioeconómico y el lugar de residencia. Comprensión verbal y memoria de trabajo son los constructos que reciben un mayor impacto del nivel socioeconómico. Se espera que futuros estudios contribuyan a la investigación de habilidades cognitivas en sectores rurales y socialmente deprivados de Chile.

The recent standardization of Wechsler Adult Intelligence Scale (WAIS) in its fourth version in Chile forces to test the impact that cultural and environmental conditions can have on people's intellectual performance. The present study compared the performance of young people from rural and urban areas of the Biobío region, segmented by parental education level as proxy variable to socioeconomic status. Results showed an interaction effect between socioeconomic status and place of residence. Verbal Comprehension and Working Memory are the constructs that received a higher impact of the socioeconomic status. Future studies are expected to contribute to research on cognitive abilities in rural and socially deprived sectors in Chile.

Crystal structure of shrimp arginine kinase in binary complex with arginine-a molecular view of the phosphagen precursor binding to the enzyme.

Arginine kinase (AK) is a key enzyme for energetic balance in invertebrates. Although AK is a well-studied system that provides fast energy to invertebrates using the phosphagen phospho-arginine, the structural details on the AK-arginine binary complex interaction remain unclear. Herein, we determined two crystal structures of the Pacific whiteleg shrimp (Litopenaeus vannamei) arginine kinase, one in binary complex with arginine (LvAK-Arg) and a ternary transition state analog complex (TSAC). We found that the arginine guanidinium group makes ionic contacts with Glu225, Cys271 and a network of ordered water molecules. On the zwitterionic side of the amino acid, the backbone amide nitrogens of Gly64 and Val65 coordinate the arginine carboxylate. Glu314, one of proposed acid-base catalytic residues, did not interact with arginine in the binary complex. This residue is located in the flexible loop 310-320 that covers the active site and only stabilizes in the LvAK-TSAC. This is the first binary complex crystal structure of a guanidine kinase in complex with the guanidine substrate and could give insights into the nature of the early steps of phosphagen biosynthesis.

Antioxidant capacity of two novel bioactive Fe(III)-cyclophane complexes.

The cyclophanes 2,9,25,32-tetraoxo-4,7,27,30-tetrakis(carboxymethyl)-1,4,7,10, 24,27,30,33-octaaza-17,40-dioxa[10.1.10.1]paracyclophane (PO) and 2,9,25,32-tetraoxo-4,7,27,30-tetrakis(carboxymethyl)-1,4,7,10,24,27,30,33-octaaza[10.1.10.1]paracyclophane (PC) were coordinated with iron to form cationic binuclear Fe(III) Fe2PO and Fe2PC complexes, respectively. Their antioxidant capacity, superoxide dismutase and peroxidase mimetic activity, as well as their toxicity toward peripheral blood mononuclear cells (PBMCs) were evaluated. Both Fe2PO and Fe2PC are interesting biomimetics with antioxidant capacity similar to that of ascorbic acid that prevent mortality in cultured PBMCs, with the potential to have bioactive and protective functions in disease animal models.

Shrimp oncoprotein nm23 is a functional nucleoside diphosphate kinase.

Biosynthesis of nucleoside triphosphates is critical for bioenergetics and nucleic acid replication, and this is achieved by nucleoside diphosphate kinase (NDK). As an emerging biological model and the global importance of shrimp culture, we have addressed the study of the Pacific whiteleg shrimp (Litopenaeus vannamei) NDK. We demonstrated its activity and affinity towards deoxynucleoside diphosphates. Also, the quaternary structure obtained by gel filtration chromatography showed that shrimp NDK is a trimer. Affinity was in the micro-molar range for dADP, dGDP, dTDP and except for dCDP, which presented no detectable interaction by isothermal titration calorimetry, as described previously for Plasmodium falciparum NDK. This information is particularly important, as this enzyme could be used to test nucleotide analogs that can block white spot syndrome virus (WSSV) viral replication and to study its bioenergetics role during hypoxia and fasting.

Antioxidant capacity of binuclear Cu(II)-cyclophanes, insights from two synthetic bioactive molecules.

The compounds 2,9,25,32-tetraoxo-4,7,27,30-tetrakis(carboxymethyl)-1,4,7,10,24,27,30,33-octaaza-17,40-dioxa[10.1.10.1]paracyclophane and 2,9,25,32-tetraoxo-4,7,27,30-tetrakis(carboxymethyl)-1,4,7,10,24,27,30,33-octaaza[10.1.10.1]paracyclophane binuclear copper complexes (Cu2PO and Cu2PC, respectively) were studied by determining their antioxidant capacity using the TROLOX equivalent antioxidant capacity (TEAC) assay, and their cytotoxicity on cultured cells, as well as the superoxide dismutase (SOD)-like activity. Cu2PO had an antioxidant capacity (0.1 g eq TROLOX mol−1) within the order of magnitude of ascorbic acid, and both, Cu2PO and Cu2PC were nontoxic to cultured peripheral mononuclear blood cells. The SOD-like activity was evaluated using the nitroblue tetrazolium assay, and both compounds presented an excellent activity: for Cu2PO, the IC50 was 52 nM and for Cu2PC an IC50 of 0.5 µM was obtained comparable to CuZn SOD IC50 17 nM (Fernandes et al., J Inorg Biochem 2007;101:849­858). These results suggest that synthetic binuclear macrocycles are good candidates to be used as synthetic bioactive molecules with applications in biomedicine.

Role of an invariant lysine residue in folate binding on Escherichia coli thymidylate synthase: calorimetric and crystallographic analysis of the K48Q mutant.

Thymidylate synthase (TS) catalyzes the reductive methylation of deoxyuridine monophosphate (dUMP) using methylene tetrahydrofolate (CH(2)THF) as cofactor, the glutamate tail of which forms a water-mediated hydrogen bond with an invariant lysine residue of this enzyme. To understand the role of this interaction, we studied the K48Q mutant of Escherichia coli TS using structural and biophysical methods. The k(cat) of the K48Q mutant was 430-fold lower than wild-type TS in activity, while the K(m) for the (R)-stereoisomer of CH(2)THF was 300 microM, about 30-fold larger than K(m) from the wild-type TS. Affinity constants were determined using isothermal titration calorimetry, which showed that binding was reduced by one order of magnitude for folate-like TS inhibitors, such as propargyl-dideazafolate (PDDF) or compounds that distort the TS active site like BW1843U89 (U89). The crystal structure of the K48Q-dUMP complex revealed that dUMP binding is not impaired in the mutant, and that U89 in a ternary complex of K48Q-nucleotide-U89 was bound in the active site with subtle differences relative to comparable wild-type complexes. PDDF failed to form ternary complexes with K48Q and dUMP. Thermodynamic data correlated with the structural determinations, since PDDF binding was dominated by enthalpic effects while U89 had an important entropic component. In conclusion, K48 is critical for catalysis since it leads to a productive CH(2)THF binding, while mutation at this residue does not affect much the binding of inhibitors that do not make contact with this group.