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Green Synthesis and Physical and Chemical Characterization of Chitosans with a High Degree of Deacetylation, Produced by a Binary Enzyme System

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Journal of Life Sciences 2014年第3期8卷 276-282页

作者： Laidson Paes Gomes Cristina Tristao Andrade Joab Trajano Silva eduardo Mere del Aguila Vania Margaret Flosi Paschoalin Institute of Chemistry University Federal of Rio de Janeiro Rio de Janeiro 21941-909 R J Brazil Institute of Macromolecules Professora Eloisa Mano University Federal of Rio de Janeiro Rio de Janeiro 21945-598 R J Brazil

Chitosan is a biopolymer obtained from chitin, where the N-acetylglucosamine monomer is in its deacetylated form; this polymer is useful for a wide variety of industrial applications. The properties and uses of chitosan depend on its physical and chemical characteristics, which result from the treatments used for its production. In this study, we report the preparation and characterization ofchitosan oligosaccharides by a green synthesis from crystalline shrimp chitin, using a sequential enzyme treatment by chitinase and chitin deacetylase. Chitinases were purified from grapes and used to rupture the crystalline shrimp chitin structure, modifying the crystallinity index from 57.6% to 15.9%. The resultant polymers were deacetylated using a recombinant chitin deacetylase from Saccharomyces cerevisiae, which was cloned and expressed in Pichia pastoris. The chitosans produced showed an estimated DA （degree of acetylation） of approximately 20%, and the molecular weights ranged from -7,600 to -3,700 after treatment in pH 3.0 and pH 6.0 for 10 min and 40 min, respectively. Physical and chemical characterization of the products indicated that enzyme fragmentation of chitin probably makes the acetamide groups more accessible to deacetylation, forming homogeneous polymers that are free of hazardous sub-products, have defined low molecular weights, and are highly deacetylated.

关键词： Chitosan binary enzyme system chitinases recombinant chitin deacetylase low acetylation degree low molecular weight.

Is the EGFR pathway relevant for the pathogenesis but not for treatment of acute myeloid leukemia?

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Journal of Cancer Metastasis and Treatment 2021年第1期7卷 765-774页

作者： Luciana Yamamoto de Almeida eduardo Magalhães Rego Center for Cell-based Therapy University of Sao PauloRibeirao PretoSao Paulo CEP 14051-140Brazil Hematology Division LIM31Faculdade de MedicinaUniversity of Sao PauloSao Paulo CEP 05403-000Brazil.

Despite intense research and the development of several new chemotherapeutics,the prognosis for specific subsets of acute myeloid leukemia(AML)has not improved ***,the investigation of signaling pathways associated with the pathogenesis and progression of AML has become a source for the discovery of more effective *** epidermal growth factor receptor(EGFR)belongs to the HER family of tyrosine kinase(TK)receptors and is involved in the progression of a variety of solid *** the expression of members of the HER family appears to be limited to epithelial tissues and derived neoplasms,there is evidence demonstrating their role in hematopoiesis and hematological *** AML,preclinical studies and two anecdotal cases of response to EGFR TK inhibitors(TKI)supported the EGFR signaling pathway as a potential therapeutic ***,the presence of EGFR ligands in the bone marrow microenvironment has been shown to play pathological and regenerative/protective roles in ***,data reporting the expression of EGFR in AML remain controversial and the EGFR pathway inhibition in AML patients has demonstrated limited clinical *** studies are required to determine the relevance of the EGFR pathway in AML biology and which patients may benefit from using EGFR TKI or other drugs that target TK receptors.

关键词： Acute myeloid leukemia epidermal growth factor receptor EGFR ligands EGFR tyrosine kinase inhibitors gefitinib erlotinib

Biocatalytic production of chitosan polymers from shrimp shells,using a recombinant enzyme produced by Pichia pastoris

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American Journal of Molecular Biology 2012年第4期2卷 341-350页

作者： eduardo Mere del Aguila Laidson Paes Gomes Cristina Tristao Andrade Joab Trajano Silva Vania Margaret Flosi Paschoalin Universidade Federal do Rio de Janeiro Instituto de QuímicaRio de JaneiroBrazil Universidade Federal do Rio de Janeiro Instituto de Macromoléculas Professora Eloisa ManoRio de JaneiroRJBrazil

Chitosan has a unique chemical structure with high charge density, reactive hydroxyl and amino groups, and extensive hydrogen bonding. Chitin deacetylase (EC 3.***.1.41) catalyzes the hydrolysis of the N-acetamido groups of N-acetyl-D-glucosamine residues in chitin, converting it to chitosan and releasing acetate. The entire ORF of the CDA2 gene encoding one of the two isoforms of chitin deacetylase from Saccharomyces cerevisiae was cloned in Pichia pastoris. The Tg (Cda2-6xHis)p was expressed at high levels as a soluble intracellular protein after induction of the recombinant yeast culture with methanol, and purified using nickel-nitrilotriacetic acid chelate affinity chromatography, resulting in a protein preparation with a purity of >98% and an overall yield of 79%. Chitin deacetylase activity was measured by a colorimetric method based on the O-phthalaldehyde reagent, which detects primary amines remaining in chitinous substrate after acetate release. The recombinant enzyme could deacetylate chitin, chitobiose, chitotriose and chitotetraose, with an optimum temperature of 50°C and pH 8.0, determined using oligochitosaccharides as the substrates. The recombinant protein was also able to deacetylate its solid natural substrate, shrimp chitin, to a limited extent, producing chitosan with a degree of acetylation (DA) of 89% as determined by Fourier transform infrared spectroscopy. The degree of deacetylation was increased by pre-hydrolysis of crystalline shrimp chitin by chitinases, which increased the deacetylation ratio triggered by chitin deacetylase, producing chito-oligosaccharides with a degree of acetylation of 33%. The results described here open the possibility to use the rCda2p, combined with chitinases, for biocatalytic conversion of chitin to chitosan with controlled degrees of deacetylation. We show herein that the crystalline chitin form can be cleanly produced in virtually quantitative yield if a combined and sequential enzyme treatment is performed.

关键词： Chitin Deacetylase Chitosan Chitin Pichia Pastoris Deacetylation Degree

Mapping fractional landscape soils and vegetation components from Hyperion satellite imagery using an unsupervised machinelearning workflow

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International Journal of Digital Earth 2018年第7期11卷 670-690页

作者： Michael J.Friedel Massimo Buscema Luiz eduardo Vicente Fabio Iwashita Andréa Koga-Vicente Hydrogeology Department GNS ScienceLower HuttNew Zealand Mathematical&Statistical Sciences University of ColoradoDenverCOUSA Semeion Institute RomeItaly Satellite Monitoring Unit Brazilian Corporation of Agricultural Research-EMBRAPACampinasBrazil Earth Sciences Department University of FlorenceFlorenceItaly Center for Meteorological and Climatological Research in Agriculture University of CampinasCampinasBrazil

An unsupervised machine-learning workflow is proposed for estimating fractional landscape soils and vegetation components from remotely sensed hyperspectral *** workflow is applied to EO-1 Hyperion satellite imagery collected near Ibirací,Minas Gerais,*** proposed workflow includes subset feature selection,learning,and estimation *** training with landscape feature class realizations provide a hypersurface from which to estimate mixtures of soil(e.g.0.5 exceedance for pixels:75%clay-rich Nitisols,15%iron-rich Latosols,and 1%quartz-rich Arenosols)and vegetation(e.g.0.5 exceedance for pixels:4%Aspen-like trees,7%Blackberry-like trees,0%live grass,and 2%dead grass).The process correctly maps forests and iron-rich Latosols as being coincident with existing drainages,and correctly classifies the clay-rich Nitisols and grasses on the intervening *** classifications are independently corroborated visually(Google Earth)and quantitatively(random soil samples and crossplots of field spectra).Some mapping challenges are the underestimation of forest fractions and overestimation of soil fractions where steep valley shadows exist,and the under representation of classified grass in some dry areas of the Hyperion *** preliminary results provide impetus for future hyperspectral studies involving airborne and satellite sensors with higher signal-to-noise and smaller footprints.

关键词： Hyperspectral machine learning remote sensing soils and vegetation unsupervised workflow

Deadly oasis:Recurrent annihilation of Cretaceous desert bryophyte colonies;the role of solar,climate and lithospheric forcing

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Geoscience Frontiers 2021年第1期12卷 1-12页

作者： Juan Pedro Rodríguez-Lópeza eduardo Barrón Daniel Peyrot Gary B.Hughes Department of Geology.Faculty of Science.United Arab Emirates University.50009.Al Ain Abu DhabiUnited Arab Emirates Instituto Geológico y Minero de Espana(IGME) Ríos Rosas 23E-28003MadridSpain School of Earth and Environment University of Western Australia.6101CrawleyWestern AustraliaAustralia Centre for Energy Geosciences University of Western Australia.6101CrawleyWestern AustraliaAustralia Physics Department University of CaliforniaSanta BarbaraCA93106USA

Many oases(wet interdunes)are sedimentary systems characterized by high-frequency water-level oscillations,marked changes in salinity and intense biological activity at their *** are considered to be one of the most challenging environments on Earth for ecosystem *** dynamic,depositional settings are usually unfavourable for fossilization and subsequent preservation of vegetal *** paper describes bryophyte(liverwort)assemblages occurring in three successive horizons interpreted to represent(i)recurrent early successional phases of biological soil crust colonization of wet interdune margins or(ii)exceptional preservation of floating or riparian liverworts in oasis pond waters associated with a progressive fall of the interdune water *** record of in situ colonization surfaces characterized by delicate(***-free)three-dimensional structures represents an exceptional type of preservation herein associated with a rapid variation in phreatic interdune water level and the subsequent establishment of anoxic and reducing *** occurrence of exceptionally preserved liverwort colonies coincides with the sedimentary record of,at least,three seismite levels in the *** gathered from the site suggests that the water table of the oasis was controlled by a combination of(i)a positive creation of accommodation space due to subsidence associated with movement on syn-sedimentary extensional faults,and(ii)the rise and fall of the oasis water table controlled by the oscillations of the groundwater system due to orbital changes which appear to drive the variability of the climate *** groundwater levels flooded the oasis soil crusts and lead to the exceptional recurrent preservation of liverwort colonies at the oasis ***,considering the hypothesis of floating or riparian liverworts in the oasis pond waters,the fall in the level of the oasis water table placed the floating liverworts in contact with the

关键词： Oasis Cretaceous Liverworts Colonies Extensional tectonics Solar cyclicity

Methods for the analysis of neuronal plasticity and brain connectivity during neurological recovery

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Neural Regeneration Research 2016年第11期11卷 1701-1703页

作者： eduardo H.Sanchez-Mendoza Tayana Silva de Carvalho Dirk M.Hermann Department of Neurology University of Duisburg-Essen

The study of neuronal plasticity under pathological conditions is now a major point of focus on the field of neurological recovery. After the repeated failure of acute neuroprotection strategies for stroke treatment, the design of studies aimed at promoting the reconstruction of neuronal networks has become essential. Methods for the delivery of therapeutic agents on a steady dosage, thus preventing pharmacological peaks or excessive manipulation of experimental animals, are thus required. Additionally, methods that allow the visualization of neurological remodeling processes are fundamental to the understanding of how a therapeutic agent exerts its function. Here we describe how the use of miniosmotic pumps for the steady delivery of such agents, together with tract tracer injections, can be combined to unveil important information on how the brain changes after stroke and how therapeutic agents promote brain remodeling recovery.

关键词： stroke blood brain barrier neuroplasticity drug delivery

Differential responses to artificial selection on oviposition site preferences in Drosophila melanogaster and D. simulans

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Insect Science 2015年第6期22卷 821-828页

作者： eduardo M. Soto Maria I. L. Betti Juan Hurtado Esteban Hasson Departamento de Ecologia Genetica y Evolucion IEGEBA (CONICET-UBA) Facultad de Ciencias Exactas y Naturales Universidad deBuenos Aires Buenos Aires Argentina

The preference-performance relationship in plant-insect interactions is a cen- tral theme in evolutionary ecology. Among many insects, eggs are vulnerable and larvae have limited mobility, making the choice of an appropriate oviposition site one of the most important decisions for a female. We investigated the evolution of oviposition preferences in Drosophila melanogaster Meigen and Drosophila simulans Sturtevant by artificially selecting for the preference for 2 natural resources, grape and quince. The main finding of our study is the differential responses of D. melanogaster and D. simulans. Although preferences evolved in the experimental populations of D. melanogaster, responses were not consistent with the selection regimes applied. In contrast, responses in D. simulans were consistent with expectations, demonstrating that this species has selectable genetic variation for the trait. Furthermore, crosses between D. simulans divergent lines showed that the genetic factors involved in grape preference appear to be largely recessive. In summary, our artificial selection study suggests that D. melanogaster and D. simulans possess different genetic architectures for this trait.

关键词： artificial selection behavior Drosophila genetic variation naturalresources oviposition preference

Variable-top stem biomass equations at tree-level generated by a simultaneous density-integral system for second growth forests of roble, raulí,and coigüe in Chile

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Journal of Forestry Research 2019年第3期30卷 993-1010页

作者： Carlos Valenzuela eduardo Acuna Alicia Ortega Geronimo Quinonez-Barraza Jose Corral-Rivas Jorge Cancino Departamento Manejo de Bosques y Medio Ambiente Facultad de Ciencias ForestalesUniversidad de Concepcion Victoria 631Barrio Universitario4070386 ConcepcionChile Instituto de Bosques y Sociedad Facultad de Ciencias Forestales y Recursos NaturalesUniversidad Austral de ChileCampus Isla Teja5110566 ValdiviaChile Campo Experimental Valle del Guadiana Instituto Nacional de Investigaciones Forestales Agricolas y Pecuarias (INIFAP)km 4.5 Carretera Durango-Mezquital34170 DurangoDGOMexico Instituto de Silvicultura e Industria de la Madera Universidad de Juarez del Estado de Durango34120 DurangoMexico

Variable-top stem biomass models at the tree level for second growth forests of roble (Nothofagus obliqua), rauli(Nothofagus alpina), and coigüe (Nothofagus dombeyi) were fitted by a simultaneous density-integral system, which combines a stem taper model and a wood basic density model. For each model, an autoregressive structure of order 2 and a power equation of residual variance were incorporated to reduce residual autocorrelation and heteroscedasticity, respectively. By using dummy variables in the regression analysis, zonal effects on the parameters in the variable-top stem biomass equations were detected in roble. Consequently, equations for clusters of zones were obtained. These equations presented significant parameters and a high precision in both fitting and validation processes (i.e., CV<11.5% and CVp<11.9%, respectively), demonstrating that they are unbiased. The advantage of these types of functions is that they provide estimates of volume and biomass of sections of the stem, defined between any two points of the stem in the three species. Thus, depending on the final use of the wood and the dimensions of the tree, a stem fraction can be quantified in units of volume and the remaining fraction in units of weight.

关键词： Autocorrelation Density-integral Dummy variables Autoregressive error structure Heteroscedasticity

Recovery of valuable metals from waste cables by employing mechanical processing followed by spouted bed elutriation

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Particuology 2019年第4期17卷 74-80页

作者： eduardo H. Tanabe Roger M. Silva Daliomar L. Oliveira Junior Daniel A. Bertuol Environmental Processes Laboratory (LAPAM) Chemical Engineering Department Federal University of Santa Maria - UFSM Santa Maria RS Brazil

Cables and wires, which are essential parts of equipment for the transmission of both information and electricity, contain valuable materials including copper (Cu) and aluminum (Al). This experimental work evaluates the use of mechanical processing (grinding and sieving), followed by spouted bed elutriation, for separation of the valuable materials (steel-coated copper, copper, and aluminum) present in waste coaxial and internet cables. A recovery efficiency of approximately 90% was achieved for the steel-coated copper in coaxial cables. For in ternet cables, the copper recovery efficiency was approximately 87%. These findings dem on strate that it is possible to separate, recover, and recycle the valuable materials (metals) present in waste cables using simple, low-cost, and efficient mechanical processing followed by spouted bed elutriation.

关键词： Waste cable Elutriation Copper Recycling Mechanical process