4,502 research outputs found
Structure of concanavalin A at pH 8: bound solvent and crystal contacts
9 pages, 3 figures, 4 tables.Concanavalin A has been crystallized in the presence of the ligand (6-S-[beta]-D-galactopyranosyl-6-thio)-cyclomaltoheptaose. The crystals are isomorphous to those reported for ConA complexed with peptides at low resolution (3.00-2.75 Å). The structure was solved at 1.9 Å, with free R and R values of 0.201 and 0.184, respectively. As expected, no molecules of the ligand were bound to the protein. Soaking in the cryobuffer left its fingerprint as 25 molecules of glycerol in the bound solvent, most of them at specific positions. The fact that a glycerol molecule is located in the sugar-binding pocket of each of the four subunits in the asymmetric unit and another is located in two of the peptide-binding sites suggests a recognition phenomenon rather than a displacement of water molecules by glycerol. Crystal contact analysis shows that a relation exists between the residues that form hydrogen bonds to other asymmetric units and the space group: contact Asp58-Ser62 is a universal feature of ConA crystals, while Ser66-His121, Asn69-Asn118 and Tyr100-His205 contacts are general features of the C2221 crystal form.We thank Professor GarcõÂa-Ruiz for his constant support and helpful discussions and suggestions, Dr Cartwright for reviewing the manuscript and Professor Kabsch for providing
XDS free of charge.We acknowledge EMBO/DESY for beam time, Professor Martinez Ripoll for his kind support in the preliminary X-ray characterization using the rotating-anode
generator at the Instituto de QuõÂmica Fisica Roca Solano (CSIC) and the referees for valuable comments.Work in AA's laboratory is funded by Spanish Plan Nacional grant BMC-
2002-04011-C03.Peer reviewe
Revalorización de residuos de equipos eléctricos y electrónicos en Colombia: una alternativa para la obtención de metales preciosos y metales para la industria
This article aims to review the global context, and especially the Colombian context, regarding the management of waste electrical and electronic appliances, their use, recovery and the main extraction methods for high added-value base and precious metals. A literature review was carried out to obtain the quantities of residues, their main components and the extraction methods for base and precious metals; for Colombia, a case study was carried out in which, through a hydrometallurgy process applied to cellular phones, the quantities of base and precious metals that can be obtained were calculated. Only 15.5 % of e-waste in the world is recycled, the main recyclable components are iron (Fe), copper (Cu), aluminum (Al), lead (Pb), nickel (Ni), silver (Ag), gold (Au) and palladium (Pd), and that using e-waste as a source of metals could reduce energy consumption by 60-95 %. For the case study in Colombia, it was found that 3.8 t/year of Cu, 3.5 t/year of Fe, 56.5 kg/year of Ag, 6 kg/year of Pd and 10 kg/year of Au could be obtained. The conclusion is that recovering metals from electrical and electronic waste is feasible and that alternatives should be sought to take advantage of them due to their potential added value.El objetivo de este artÃculo es revisar el contexto mundial, y especialmente el colombiano, respecto al manejo de los residuos de equipos eléctricos y electrónicos, su aprovechamiento, recuperación y los principales métodos para la extracción de metales base y preciosos de alto valor agregado. Para ello, se realizó una revisión bibliográfica para obtener las cantidades de residuos, sus componentes principales y los métodos de extracción de metales base y preciosos; para Colombia, se realizó un estudio de caso, en el que, mediante un proceso de hidrometalurgia aplicado a teléfonos celulares, se calcularon las cantidades de metales base y preciosos que se pueden obtener. Se encontró que solo se aprovecha el 15,5 % de los residuos electrónicos en el mundo, que los principales componentes reciclables son el hierro (Fe), el cobre (Cu), el aluminio (Al), el plomo (Pb), el nÃquel (Ni), la plata (Ag), el oro (Au) y el paladio (Pd), y que el uso de los residuos electrónicos como fuente de metales podrÃa reducir el consumo de energÃa entre 60 % y 95 %. Para el estudio de caso en Colombia, se encontró que se podrÃan obtener 3,8 t/año de Cu, 3,5 t/año de Fe, 56,5 kg/año de Ag, 6 kg/año de Pd y 10 kg/año de Au. Se concluye que es viable la recuperación de metales a partir de residuos eléctricos y electrónicos y que se deben buscar alternativas para aprovecharlos debido a su potencial valor agregado
Thermal Diffusion of a Two Layer System
In this paper thermal conductivity and thermal diffusivity of a two layer
system is examined from the theoretical point of view. We use the one
dimensional heat diffusion equation with the appropriate solution in each layer
and boundary conditions at the interfaces to calculate the heat transport in
this bounded system. We also consider the heat flux at the surface of the samle
as boundary condition instead of using a fixed tempertaure. From this, we
obtain an expression for the efective thermal diffusivity of the composite
sample in terms of the thermal diffusivity of its constituent materials
whithout any approximations.Comment: 16 pages, 1 figure, RevTeX v. 3.0 macro packag
Comparative pattern of Octopus vulgaris life cycle with environmental parameters in the Northern Alboran Sea (Western Mediterranean Sea)
Versión del edito
Effect of chitosan essential oil films on the storage-keeping quality of pork meat products
Edible films based on chitosan were prepared, with
and without basil or thyme essential oils, with the aim of
assessing their protective ability against lipid oxidation and
their antimicrobial activity. Chitosan films had good oxygenbarrier
properties, which were worsened by essential oil addition,
especially when the film equilibrium moisture content
increased. Due to the oxygen-barrier effect, all the films
effectively protected pork fat from oxidation, in comparison
to unprotected samples. In spite of the worsening of the
oxygen-barrier properties, the films with essential oils were
more effective than those of pure chitosan, which points to the
chemical action of specific antioxidant compounds of the oils.
Films were effective to control microbial growth in minced
pork meat, although the incorporation of essential oils did not
improve their antimicrobial activity. Throughout the storage,
the films led to colour changes in minced pork meat associated
with the conversion of myoglobin into metmyoglobin due to
the reduction of the oxygen availability.The authors acknowledge the financial support provided by the Universitat Politecnica de Valencia (PAID-06-09-2834), Generalitat Valenciana (GV/2010/082) and Ministerio de Educacion y Ciencia (AGL2010-20694). Author J. Bonilla is deeply grateful to Generalitat Valenciana for a Santiago Grisolia Grant.Bonilla Lagos, MJ.; Vargas, M.; Atarés Huerta, LM.; Chiralt Boix, MA. (2014). Effect of chitosan essential oil films on the storage-keeping quality of pork meat products. Food and Bioprocess Technology. 7(8):2443-2450. https://doi.org/10.1007/s11947-014-1329-3S2443245078ASTM D3985. (1995). Standard test method for oxygen gas transmission rate through plastic films and sheeting using a coulometric sensor. West Conshohocken: American Society for Testing and Materials.Atarés, L., Pérez-Masiá, R., & Chiralt, A. (2011). The role of some antioxidants in the HPMC film properties and lipid protection in coated toasted almonds. 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Antibacterial activity of oregano and thyme essential oils against Listeria monocytogenes and Escherichia coli O157:H7 in feta cheese packaged under modified atmosphere. LWT - Food Science and Technology, 44, 1240–1244.Han, J. H., & Gennadios, A. (2005). Edible films and coatings: a review. In J. H. Han (Ed.), Innovations in Food Packaging (pp. 39–262). Oxford: Elsevier Academic.Kim, J., Marshall, M. R., & Wei, C. I. (1995). Antibacterial activity of some essential oil components against five foodborne pathogens. Journal of Agricultural and Food Chemistry, 43, 2839–2845.Labuza, T. P. (1980). The effect of water activity on reaction kinetics of food deterioration. Food Technology, 34, 36–41.Mancini, R. A., & Hunt, M. C. (2005). Current research in meat color. Meat Science, 71, 100–121.Moure, A., Cruz, J. M., Franco, D., Dominguez, J. M., Sineiro, J., Dominguez, H., et al. (2001). Natural antioxidants from residual sources. Food Chemistry, 72, 145–171.Rao, M. S., Chander, R., & Sharma, A. (2005). Development of shelf-stable intermediate moisture meat products using active edible chitosan coating and irradiation. Journal of Food Science, 70, 325–331.Salame, M. (1986). Barrier polymers. In M. Bakker (Ed.), The Wiley encyclopedia of packaging technology (pp. 48–54). New York: Wiley.Sánchez-González, L., González-MartÃnez, C., Chiralt, A., & Cháfer, M. (2010). Physical and antimicrobial properties of chitosan–tea tree essential oil composite films. Journal of Food Engineering, 98, 443–452.Sánchez-González, L., Vargas, M., González-MartÃnez, C., Chiralt, A., & Cháfer, M. (2011a). Use of essential oils in bioactive edible coatings. Food Engineering Reviews, 3, 1–16.Sánchez-González, L., Cháfer, M., Hernández, M., Chiralt, A., & González-MartÃnez, C. (2011b). Antimicrobial activity of polysaccharide films containing essential oils. Food Control, 22, 1302–1310.Seydim, A. C., & Sarikus, G. (2006). 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Investigating mutations in the genes GDF9 and BMP15 in Pelibuey sheep through the amplification-refractory mutation system with tetra-primers
Single Nucleotide Polymorphisms (SNP) or mutations are variations with a broad distribution in the genome and, as part of genetic studies, SNP allow the identification of allelic variants related to characteristics of economic importance in sheep production. However, the identification of SNP and their genotypes through sequencing is expensive, as it requires specialized materials and equipment. The objective of this study was to identify polymorphisms and their genotypes in the growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) genes in Pelibuey sheep using the tetra-primer amplification-refractory mutation system through polymerase chain reaction (T-ARMS-PCR). DNA extraction and amplification of BMP15 and GDF9 were conducted from blood samples contained in WhatmanTM FTATM cards from 60 multiparous Pelibuey ewes with reproductive records. The T-ARMS-PCR methodology allowed the identification of wild-type genotypes and mutated homozygous genotypes in polymorphisms G4 and G6 of GDF9, whereas mutations in the BMP15 gene were not found. These results were confirmed by sequencing. In conclusion, the T-ARMS-PCR methodology allowed the identification of mutated and wild-type genotypes in SNP G4 and G6 of GDF9, although no mutations were found in BMP15 in Pelibuey sheep. This technique was found to be reliable, rapid, and easily applied to identify polymorphic genotypes
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