Evaluation of cross-linked aggregates from purified Bacillus subtilis levansucrase mutants for transfructosylation reactions

BACKGROUND: Increasing attention has been focused on inulin and levan-type oligosaccharides, including fructosyl-xylosides and other fructosides due to their nutraceutical properties. Bacillus subtilis levansucrase (LS) catalyzes the synthesis of levan from sucrose, but it may also transfer the fructosyl moiety from sucrose to acceptor molecules included in the reaction medium. To study transfructosylation reactions with highly active and robust derivatives, cross-linked enzyme aggregates (CLEAs) were prepared from wild LS and two mutants. CLEAs combine the catalytic features of pure protein preparations in terms of specific activity with the mechanical behavior of industrial biocatalysts. RESULTS: Two types of procedures were used for the preparation of biocatalysts from purified wild type LS (WT LS) B. subtilis and the R360K and Y429N LS mutants: purified enzymes aggregated with glutaraldehyde (cross-linked enzyme aggregates: CLEAs), and covalently immobilized enzymes in Eupergit C(®). The biocatalysts were characterized and used for fructoside synthesis using xylose as an acceptor model. CLEAs were able to catalyze the synthesis of fructosides as efficiently as soluble enzymes. The specific activity of CLEAs prepared from wild type LS (44.9 U/mg of CLEA), R360K (56.5 U/mg of CLEA) and Y429N (1.2 U/mg of CLEA) mutants were approximately 70, 40 and 200-fold higher, respectively, than equivalent Eupergit C(® )immobilized enzyme preparations (U/mg of Eupergit), where units refer to global LS activity. In contrast, the specific activity of the free enzymes was 160, 171.2 and 1.5 U/mg of protein, respectively. Moreover, all CLEAs had higher thermal stability than corresponding soluble enzymes. In the long term, the operational stability was affected by levan synthesis. CONCLUSION: This is the first report of cross-linked transglycosidases aggregates. CLEAs prepared from purified LS and mutants have the highest specific activity for immobilized fructosyltransferases (FTFs) reported in the literature. CLEAs from R360K and Y429N LS mutants were particularly suitable for fructosyl-xyloside synthesis as the absence of levan synthesis decreases diffusion limitation and increases operational stability

Identification of a potential allosteric site of Golgi α-mannosidase II using computer-aided drug design

Golgi α-mannosidase II (GMII) is a glycoside hydrolase playing a crucial role in the N-glycosylation pathway. In various tumour cell lines, the distribution of N-linked sugars on the cell surface is modified and correlates with the progression of tumour metastasis. GMII therefore is a possible molecular target for anticancer agents. Here, we describe the identification of a non-competitive GMII inhibitor using computer-aided drug design methods including identification of a possible allosteric binding site, pharmacophore search and virtual screening.publishedVersio

La enseñanza de la Estadística Inferencial. Un estudio de caso en la Pontificia Universidad Javeriana Cali

El presente artículo es el resultado sobre la investigación de tipo descriptiva que busca caracterizar la práctica pedagógica de los docentes de Estadística Inferencial en las ca- rreras de Administración de Empresas, Psicología e Ingeniería Industrial de la Pontifi- cia Universidad Javeriana Cali. Las fuentes de información las constituyeron los docen- tes del curso y sus respectivos estudiantes. Para la recolección de los datos se utilizaron entrevistas semiestructuradas, cuestionarios para los estudiantes, observaciones de al- gunas clases y documentos institucionales. Los datos de cada profesor fueron condensa- dos en una plantilla general de doble entrada, constituida por categorías pedagógicas, indicadores de mayor interés para el estudio y fuentes de información. A partir de esta plantilla se diseña una matriz con las categorías educativas: planeación, ejecución y evaluación, correspondientes a las filas, y los factores pedagógicos de descripción: obje- tivos, contenidos, estrategias pedagógicas y evaluación del aprendizaje, correspondien- tes a las columnas. Dicha matriz permitió analizar y conceptualizar la práctica pedagógi- ca de cada profesor . A partir del análisis y la discusión de los resultados se encontró que la práctica pedagógica de los tres docentes está mediada por las políticas institucionales y el estilo del profesor . A su vez, dicha práctica posee marcados elementos característi- cos de los modelos tradicionales, transmisionista conductista y , en menor escala, de los modelos de autoestructuración. Por tanto, se reconoce que los docentes no están inmer - sos en un modelo pedagógico único, sino que su práctica posee características de diver - sos modelos

A C˄S-cyclometallated gold(III) complex as novel antibacterial candidate against drug-resistant bacteria

The worldwide emergence and spread of infections caused by multidrug-resistant bacteria endangers the efficacy of current antibiotics in the clinical setting. The lack of new antibiotics in the pipeline points to the need of developing new strategies. Recently, gold-based drugs are being repurposed for antibacterial applications. Among them, gold(III) complexes have received increasing attention as metal-based anticancer agents. However, reports on their antibacterial activity are scarce due to stability issues. The present work demonstrates the antibacterial activity of the gold(III) complex 2 stabilized as C∧S-cycloaurated containing a diphenylphosphinothioic amide moiety, showing minimum inhibitory concentration (MIC) values that ranged from 4 to 8 and from 16 to 32 mg/L among Gram-positive and Gram-negative multidrug-resistant (MDR) pathogens, respectively. Complex 2 has a biofilm inhibitory activity of only two to four times than its MIC. We also describe for the first time a potent antibacterial synergistic effect of a gold(III) complex combined with colistin, showing a bactericidal effect in less than 2 h; confirming the role of the outer membrane as a permeability barrier. Complex 2 shows a low rate of internalization in Staphylococcus aureus and Acinetobacter baumannii; it does not interact with replication enzymes or efflux pumps, causes ultrastructural damages in both membrane and cytoplasmic levels, and permeabilizes the bacterial membrane. Unlike control antibiotics, complex 2 did not generate resistant mutants in 30-day sequential cultures. We detected lower cytotoxicity in a non-tumoral THLE-2 cell line (IC50 = 25.5 μM) and no acute toxicity signs in vivo after an i.v. 1-mg/kg dose. The characterization presented here reassures the potential of complex 2 as a new chemical class of antimicrobial agents

Oligodendrogenesis in iron-deficient rats: Effect of apotransferrin

In rats, iron deficiency produces an alteration in myelinformation. However, there is limited information on theeffects of this condition on oligodendroglial cell (OLGc)proliferation and maturation. In the present study, wefurther analyzed the hypomyelination associated withiron deficiency by studying the dynamics of oligodendrogenesis.Rats were fed control (40 mg Fe/kg) oriron-deficient (4 mg Fe/kg) diets from gestation day 5until postnatal day 3 (P3) or 11 (P11). OLGc proliferation,migration and differentiation were investigatedbefore and after an intracranial injection of apotransferrinat 3 days of age (P3). The proliferating cell populationwas evaluated at P3. Iron-deficient (ID) animalsshowed an increase in the oligodendrocyte precursorscell (OPC) population in comparison with controls. Theoverall pattern of migration of cells labeled with BrdUwas investigated at P11. Iron deficiency increased theamount of BrdU1 cells in the corpus callosum (CC) anddecreased OLGc maturation and myelin formation.Changes in nerve conduction were analyzed by measuringvisual evoked potentials. Latency and amplitudewere significantly disturbed in ID rats compared withcontrols. Both parameters were substantially normalizedwhen animals were treated with a single intracranialinjection of 350 ng apotransferrin (aTf). The currentresults give support to the idea that iron deficiencyincreases the number of proliferating and undifferentiatedcells in the CC compared with the control. Treatmentwith aTf almost completely reverted the effects ofiron deficiency, both changing the migration patternand increasing the number of mature cells in the CCand myelin formation.Fil: Rosato Siri, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Badaracco, M. E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Ortiz, E. H.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Belforte, Nicolás Adalberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Estudios Farmacológicos y Botánicos. Universidad de Buenos Aires. Facultad de Medicina. Centro de Estudios Farmacológicos y Botánicos; ArgentinaFil: Guardia Clausi, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Soto, Eduardo Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Bernabeu, Ramon Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Pasquini, Juana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentin

Identification of a potential allosteric site of Golgi α-mannosidase II using computer-aided drug design

Golgi α-mannosidase II (GMII) is a glycoside hydrolase playing a crucial role in the N-glycosylation pathway. In various tumour cell lines, the distribution of N-linked sugars on the cell surface is modified and correlates with the progression of tumour metastasis. GMII therefore is a possible molecular target for anticancer agents. Here, we describe the identification of a non-competitive GMII inhibitor using computer-aided drug design methods including identification of a possible allosteric binding site, pharmacophore search and virtual screening

Stress Response to Climate Change and Postharvest Handling in Two Differently Pigmented Lettuce Genotypes: Impact on Alternaria alternata Invasion and Mycotoxin Production

Many species of Alternaria are important pathogens that cause plant diseases and postharvest rots. They lead to significant economic losses in agriculture and affect human and animal health due to their capacity to produce mycotoxins. Therefore, it is necessary to study the factors that can result in an increase in A. alternata. In this study, we discuss the mechanism by which phenol content protects from A. alternata, since the red oak leaf cultivar (containing higher phenols) showed lower invasion than the green one, Batavia, and no mycotoxin production. A climate change scenario enhanced fungal growth in the most susceptible cultivar, green lettuce, likely because elevated temperature and CO2 levels decrease plant N content, modifying the C/N ratio. Finally, while the abundance of the fungi was maintained at similar levels after keeping the lettuces for four days at 4 °C, this postharvest handling triggered TeA and TEN mycotoxin synthesis, but only in the green cultivar. Therefore, the results demonstrated that invasion and mycotoxin production are cultivar- and temperature-dependent. Further research should be directed to search for resistant cultivars and effective postharvest strategies to reduce the toxicological risk and economic losses related to this fungus, which are expected to increase in a climate change scenario.This research was funded by Basque Government IT1233-19, IT1571-22, IT1648-22, IT1682-22 and ELIKA—Basque Foundation for Agro-Food Safety

Cov-caldas: A new COVID-19 chest X-Ray dataset from state of Caldas-Colombia

The emergence of COVID-19 as a global pandemic forced researchers worldwide in various disciplines to investigate and propose efficient strategies and/or technologies to prevent COVID-19 from further spreading. One of the main challenges to be overcome is the fast and efficient detection of COVID-19 using deep learning approaches and medical images such as Chest Computed Tomography (CT) and Chest X-ray images. In order to contribute to this challenge, a new dataset was collected in collaboration with “S.E.S Hospital Universitario de Caldas” (https://hospitaldecaldas.com/) from Colombia and organized following the Medical Imaging Data Structure (MIDS) format. The dataset contains 7,307 chest X-ray images divided into 3,077 and 4,230 COVID-19 positive and negative images. Images were subjected to a selection and anonymization process to allow the scientific community to use them freely. Finally, different convolutional neural networks were used to perform technical validation. This dataset contributes to the scientific community by tackling significant limitations regarding data quality and availability for the detection of COVID-19. © 2022, The Author(s)

Clinical and microbiological characteristics of community-acquired pneumonia associated with Streptococcus pneumoniae in adult patients in Mexico

Time and risk management have always been major concerns in a continously growing number of processes and methodologies used to develop all kinds of useful products and services. Software like any other industry not only needs the most appropriate development methodology but also an efficient project management strategy that is capable of estimating and managing development times and any potential risks as best as possible in order to deliver high quality software products and services on time. Hence, the success or failure of software development projects depends on the efficiency by which several key factors such as cost, time, and risks are managed and how other software development factors influenced them. This paper presents an exploratory factor analysis to study the effects produced primarily on time planning caused by common factors observed in outsourced software development projects such as communication, teamwork, personnel training, among others. In our work, we also build a structural model in which we analyze the relationships between sets of dependent and independent variables derived from the responses of a survey applied to 32 Mexican organizations that subcontracted their software development projects to outsourcing providers. The results are presented and the reliability of our model was validated using the SmartPLS softwar