Microfotografía de rodocrosita

Microfotografía de rodocrosita proveniente de mina Santa Rita, distrito Capillitas (Provincia de Catamarca). La rodocrosita o Rosa del Inca es un carbonato de manganeso considerado como "piedra" ornamental nacional. Imagen tomada con microscopio petrográfico de luz polarizada. Escala: 500 μm

IDRC: its policy and energy activities : presented at the Symposium on International Programs during the Passive Cooling '81 Conference, Miami, 9-13 Nov., 1981

Meeting: Passive Cooling '81 Conference, 9-13 Nov. 1981, Miami, Fla., USMeeting: Symposium on International Programs, Nov. 1981, Miami, Fla., U

Real meaning of high temperature low humidity to grain storage in the Sahelian zone

Photocop

<i>Toxoplasma gondii</i> peptide ligands open the gate of the HLA class I binding groove

HLA class I presentation of pathogen-derived peptide ligands is essential for CD8+ T-cell recognition of Toxoplasma gondii infected cells. Currently, little data exist pertaining to peptides that are presented after T. gondii infection. Herein we purify HLA-A*02:01 complexes from T. gondii infected cells and characterize the peptide ligands using LCMS. We identify 195 T. gondii encoded ligands originating from both secreted and cytoplasmic proteins. Surprisingly, T. gondii ligands are significantly longer than uninfected host ligands, and these longer pathogen-derived peptides maintain a canonical N-terminal binding core yet exhibit a C-terminal extension of 1-30 amino acids. Structural analysis demonstrates that binding of extended peptides opens the HLA class I F' pocket, allowing the C-terminal extension to protrude through one end of the binding groove. In summary, we demonstrate that unrealized structural flexibility makes MHC class I receptive to parasite-derived ligands that exhibit unique C-terminal peptide extensions.Fil: McMurtrey, Curtis. University of Oklahoma; Estados UnidosFil: Trolle, Thomas. Technical University of Denmark; Dinamarca. La Jolla Institute for Allergy and Immunology; Estados UnidosFil: Sansom, Tiffany. University at Buffalo; Estados UnidosFil: Remesh, Soumya G.. La Jolla Institute for Allergy and Immunology; Estados UnidosFil: Kaever, Thomas. La Jolla Institute for Allergy and Immunology; Estados UnidosFil: Bardet, Wilfried. University of Oklahoma; Estados UnidosFil: Jackson, Kenneth. University of Oklahoma; Estados UnidosFil: McLeod, Rima. University of Chicago; Estados UnidosFil: Sette, Alessandro. La Jolla Institute for Allergy and Immunology; Estados UnidosFil: Nielsen, Morten. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentina. Technical University of Denmark; DinamarcaFil: Zajonc, Dirk M.. La Jolla Institute for Allergy and Immunology; Estados UnidosFil: Blader, Ira J. University at Buffalo; Estados UnidosFil: Peters, Bjoern. La Jolla Institute for Allergy and Immunology; Estados UnidosFil: Hildebrand, William. University of Oklahoma; Estados Unido

Direct Interrogation of Viral Peptides Presented by the Class I HLA of HIV-Infected T Cells

Identification of CD8+ cytotoxic T lymphocyte (CTL) epitopes has traditionally relied upon testing of overlapping peptide libraries for their reactivity with T cells in vitro. Here, we pursued deep ligand sequencing (DLS) as an alternative method of directly identifying those ligands that are epitopes presented to CTLs by the class I human leukocyte antigens (HLA) of infected cells. Soluble class I HLA-A*11:01 (sHLA) was gathered from HIV-1 NL4-3-infected human CD4+ SUP-T1 cells. HLA-A*11:01 harvested from infected cells was immunoaffinity purified and acid boiled to release heavy and light chains from peptide ligands that were then recovered by size-exclusion filtration. The ligands were first fractionated by high-pH high-pressure liquid chromatography and then subjected to separation by nano-liquid chromatography (nano-LC)–mass spectrometry (MS) at low pH. Approximately 10 million ions were selected for sequencing by tandem mass spectrometry (MS/MS). HLA-A*11:01 ligand sequences were determined with PEAKS software and confirmed by comparison to spectra generated from synthetic peptides. DLS identified 42 viral ligands presented by HLA-A*11:01, and 37 of these were previously undetected. These data demonstrate that (i) HIV-1 Gag and Nef are extensively sampled, (ii) ligand length variants are prevalent, particularly within Gag and Nef hot spots where ligand sequences overlap, (iii) noncanonical ligands are T cell reactive, and (iv) HIV-1 ligands are derived from de novo synthesis rather than endocytic sampling. Next-generation immunotherapies must factor these nascent HIV-1 ligand length variants and the finding that CTL-reactive epitopes may be absent during infection of CD4+ T cells into strategies designed to enhance T cell immunity

Phosphates from the La Argentina and La Rosario veins (Mina Capillitas), Catamarca

El yacimiento Mina Capillitas (Catamarca, Argentina) es un depósito del tipo epitermal polimetálico (Cu - Zn - Pb ± As - Sb - Au - Ag). Los fosfatos [fosfatos-sulfatos de aluminio (FSA), piromorfita y fluorapatita] son escasos en el depósito. Los FSA se presentan como cristales romboédricos (pseudocúbicos) con marcada zonación composicional, mostrando sustitución entre Sr y Ca, y entre P y S. Constituyen una solución sólida entre svanbergita SrAl3(SO4)(PO4)(OH)6 y crandallita CaAl3(PO4)(PO3OH)(OH)6. Los núcleos de los cristales se encuentran enriquecidos en P y Ca, los cuales disminuyen hacia los bordes en consonancia con un aumento en las concentraciones de S y Sr. Se asocian a hübnerita, tennantita-(Zn), pirita, calcopirita, enargita, galena, esfalerita y roquesita. Los cristales de piromorfita Pb5(PO4)3Cl se presentan como prismas alargados con terminaciones bipiramidales agudas, o rellenando vetillas en zonas brechadas. Es destacable su presencia dentro de masas algales colgando del techo de las galerías de la mina Santa Rita. Presenta sustitución parcial de Pb por Ca (hasta 3.32 %peso de CaO) y contenidos menores de Mn, Fe y Zn; el sitio tetraédrico está ocupado casi exclusivamente por P. La fluorapatita es magmática y es un mineral accesorio en el granito encajante de las vetas. Se presenta en cristales subhedrales a euhedrales, ricos en F (~3.5 %peso), estando el Cl por debajo del límite de detección en la mayoría de los análisis. Relaciones texturales y asociaciones minerales permiten asignar un origen hipogénico para los FSA, desarrollado durante un estadio inicial de alta sulfuración. La piromorfita tiene un origen supergénico, probablemente potenciado por la actividad microbiana en algunas yacencias.Mina Capillitas (Catamarca, Argentina) is a high to intermediate sulfidation epithermal deposit (Cu - Zn - Pb ± As - Sb - Au - Ag). Phosphates are scarce at the deposit. Studies with SEM-BSE and electron microprobe (WDS mode) confirmed the presence of aluminum phosphate-sulphates (APS), pyromorphite and fluorapatite. APS occur as rhombohedral (pseudocubic) crystals with strong compositional zoning, showing substitution between Sr and Ca, and between S and P. They are part of a solid solution dominated by svanbergite SrAl3 (SO4 )(PO4 )(OH)6 and crandallite CaAl3 (PO4 )(PO3 OH)(OH)6 . Crystal cores are enriched in P and Ca; their concentrations decrease rimwards, associated to an increase in Sr and S. APS are associated to hübnerite, tennantite-(Zn), pyrite, chalcopyrite, enargite, galena, sphalerite and roquesite. Pyromorphite Pb5 (PO4 )3 Cl occurs as long prismatic crystals showing steep bipyramids, or filling microscopic veinlets. Its occurrence within algal mats hanging from the gallery roofs at the Santa Rita Mine is remarkable. Pyromorphite shows partial substitution of Pb by Ca (up to 3.32 wt.% CaO) and minor amounts of Mn, Fe and Zn. Elements in tetrahedral coordination other than P are present in negligible amounts. Fluorapatite is magmatic and is an accessory in the granite that hosts the mineralized veins. It forms subhedral to anhedral crystals that are F-rich (~3.5 wt.%). Textural relations and mineralogical associations suggest a hypogenic origin for the APS minerals, related to an early stage of the high sulfidation mineralization. Pyromorphite has a supergenic origin, probably enhanced by microbial activity in some occurrences.Fil: Yaciuk, Pablo Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Colombo, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Lecomte, Karina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentin

Systèmes alimentaires : description du programme "Systèmes post-production" subventionné par le Centre de recherches pour le développement international

Version anglaise disponible dans la Bibliothèque numérique du CRDI : Food systems : an account of the Postproduction Systems Program supported by the International Development Research Centr

Geochemical characterization and evolution of a mountain river associated to mining activity: Capillitas stream

El arroyo Capillitas (Catamarca) es un curso de montaña que atraviesa en su cuenca alta al distrito minero Capillitas, el cual es el yacimiento argentino más diverso en especies minerales y el principal productor de rodocrosita a nivel mundial. Con el objetivo de caracterizar y analizar la evolución hidroquímica del arroyo, se tomaron muestras de agua superficial en distintos sectores de la cuenca. Los resultados mostraron aguas cálcicas, dulces (conductividad eléctrica < 0,9 mS/cm) y levemente alcalinas (pH medio = 7,6). A lo largo de su cuenca, este curso recibe el aporte de drenajes ácidos (pH de 2,5 a 4,8), los cuales modifican sus características geoquímicas, reduciendo significativamente su pH, aumentando los valores de Eh y generando cambios en la señal geoquímica disuelta.Centro de Investigaciones Geológica