Probing the Binding Site of Abl Tyrosine Kinase Using in Situ Click Chemistry

Modern combinatorial chemistry is used to discover compounds with desired function by an alternative strategy, in which the biological target is directly involved in the choice of ligands assembled from a pool of smaller fragments. Herein, we present the first experimental result where the use of in situ click chemistry has been successfully applied to probe the ligand-binding site of Abl and the ability of this enzyme to form its inhibitor. Docking studies show that Abl is able to allow the in situ click chemistry between specific azide and alkyne fragments by binding to Abl-active sites. This report allows medicinal chemists to use protein-directed in situ click chemistry for exploring the conformational space of a ligand-binding pocket and the ability of the protein to guide its inhibitor. This approach can be a novel, valuable tool to guide drug design synthesis in the field of tyrosine kinases

Calcium biomineralizations and bioerosion, its role in the biogeochemistry of soils and sediments in southeastern Buenos Aires province

Las biomineralizaciones de calcio son comunes y ampliamente distribuidas en el planeta, y son el resultado de procesos metabólicos esenciales de microorganismos, plantas y animales en ambientes continentales, litorales y marinos. Asociado a las biomineralizaciones cálcicas se hallan los procesos de bioerosión sobre la superficie y/o fisuras de los minerales y/o biominerales. Se trabajó en secuencias costeras bonaerenses, mediante técnicas de rutina. Mineralógicamente se trabajó a escala de resolución mesoscópica, microscópica y submicroscopica, la composición química se definió mediante estudios difractométricos microdispersivos (EDS). Los niveles bioclásticos asociados a la génesis de las conchillas, están todos afectados por intensa bioerosión y disolución, que reprecipitan como oxalatos, carbonatos y sulfatos de calcio, por acción de microrganismos especialmente. La actividad biológica en relación con la generación y/o degradación de componentes cálcicos en distintos ambientes, juega un rol de consideración en la biogeoquímica del calcio y su presencia como macronutriente esencial para distintos niveles tróficos de la biota en el sudeste bonaerense.Centro de Investigaciones Geológica

Calcium biomineralizations and bioerosion, its role in the biogeochemistry of soils and sediments in southeastern Buenos Aires province

Las biomineralizaciones de calcio son comunes y ampliamente distribuidas en el planeta, y son el resultado de procesos metabólicos esenciales de microorganismos, plantas y animales en ambientes continentales, litorales y marinos. Asociado a las biomineralizaciones cálcicas se hallan los procesos de bioerosión sobre la superficie y/o fisuras de los minerales y/o biominerales. Se trabajó en secuencias costeras bonaerenses, mediante técnicas de rutina. Mineralógicamente se trabajó a escala de resolución mesoscópica, microscópica y submicroscopica, la composición química se definió mediante estudios difractométricos microdispersivos (EDS). Los niveles bioclásticos asociados a la génesis de las conchillas, están todos afectados por intensa bioerosión y disolución, que reprecipitan como oxalatos, carbonatos y sulfatos de calcio, por acción de microrganismos especialmente. La actividad biológica en relación con la generación y/o degradación de componentes cálcicos en distintos ambientes, juega un rol de consideración en la biogeoquímica del calcio y su presencia como macronutriente esencial para distintos niveles tróficos de la biota en el sudeste bonaerense.Centro de Investigaciones Geológica

Calcium biomineralizations and bioerosion, its role in the biogeochemistry of soils and sediments in southeastern Buenos Aires province

Las biomineralizaciones de calcio son comunes y ampliamente distribuidas en el planeta, y son el resultado de procesos metabólicos esenciales de microorganismos, plantas y animales en ambientes continentales, litorales y marinos. Asociado a las biomineralizaciones cálcicas se hallan los procesos de bioerosión sobre la superficie y/o fisuras de los minerales y/o biominerales. Se trabajó en secuencias costeras bonaerenses, mediante técnicas de rutina. Mineralógicamente se trabajó a escala de resolución mesoscópica, microscópica y submicroscopica, la composición química se definió mediante estudios difractométricos microdispersivos (EDS). Los niveles bioclásticos asociados a la génesis de las conchillas, están todos afectados por intensa bioerosión y disolución, que reprecipitan como oxalatos, carbonatos y sulfatos de calcio, por acción de microrganismos especialmente. La actividad biológica en relación con la generación y/o degradación de componentes cálcicos en distintos ambientes, juega un rol de consideración en la biogeoquímica del calcio y su presencia como macronutriente esencial para distintos niveles tróficos de la biota en el sudeste bonaerense.Centro de Investigaciones Geológica

A lattice study of the exclusive B→K∗γB \to K^* \gamma decay amplitude, using the Clover action at β=6.0\beta=6.0

We present the results of a numerical calculation of the $B\to K^* \gamma$ form factors. The results have been obtained by studying the relevant correlation functions at $\beta=6.0$, on an $18^3 \times 64$ lattice, using the ${\rm O(a)}$-improved fermion action, in the quenched approximation. From the study of the matrix element $$ we have obtained the form factor $T_1(0)$ which controls the exclusive decay rate. The results are compared with the recent results from CLEO. We also discuss the compatibility between the scaling laws predicted by the Heavy Quark Effective Theory (HQET) and pole dominance, by studying the mass- and $q^2$-dependence of the form factors. From our analysis, it appears that the form factors follow a mass behaviour compatible with the predictions of the HQET and that the $q^2$-dependence of $T_2$ is weaker than would be predicted by pole dominance.Comment: 17 pages, LaTeX + epsf.sty. Uuencoded, compressed, tar archive including the text and one postscript figur

Silicophytoliths and taphonomy in Cenozoic pedostratigraphic sequences of the Pampean Plain, Argentina

Grasslands and savannas occupy one forth of the total surface of South America continent, and within it, the Pampean plain region, located in the central area of eastern Argentina, covers an area of 1,200,000 km2. The dominant soils are Mollisolls generally deep, developed from well-drained loessic parental material and characterized by a silty-loam texture. Pampean Plains is one of the most fertile regions of the world. Intense agricultural activities are carried out there and this, in turn, has strongly modified the native plant communities, especially grasslands. Depending on the environmental and pedological conditions, silicophytoliths are affected by diverse taphonomical processes, both in natural and anthropic environments. They can be preserved, dissolved or fragmented, and also be transported by different agents (wind, water, animals and people). Other taphonomical aspects also important to evaluate are the methodologies used in silicophytolith studies, from soil sampling to studies at a submicroscopic level. There are several current methodologies and the work is essentially done at a very detailed resolution level, which could lead to interpretation errors if the environmental or paleoenvironmental context of the study material is unknown or not clearly stated. The study area is located in regional geomorphological units from Pampean Plain, Argentina, and integrated profiles representative of typical pedoestratigraphic sequences were analyzed. Silicophytoliths were analyzed as part of the whole mineralogy of the soil samples and morphologies were described under optical and scanning electron microscopes. The results show high amounts of silicophytoliths which have been affected by various physical and chemical alteration and/or by taphonomic processes of different types and degrees of intensity. The percentage and number of silicophytoliths per gram of soil vary. In superficial horizons (O, A), the percentage ranged between 10-65%, with 11.000.000-30.000.000 phytoliths per gram of soil (n/g.s). In subsuperficial horizons (AC, B, BC) between 2-6% and 1.000.000-5.000.000 silicophytoliths n/g.s were observed. The percentage of silicophytoliths in loessic parent material (C) ranges between 0.4-2%, with 500.000-2.000.000 n/g.s. In paleosols, percentages range between 1-8%, and the number of silicophytoliths per gram of soils were 1.500.000-8.000.000. Silica and silicophytolith biomass content per ha of soil varied according C biomass, in the pedostratigraphic Cenozoic sequences from Pampean plains. Our data show that the content of silicophytoliths decreases between 50 and 95% from superficial to subsuperficial soil horizons due to pedological processes. The comprehension of the physico-chemical degradation and transference processes within silicophytolith-plant-soil-environment system is essential in order to evaluate the role of taphonomical processes in the biogeochemical cycle of silicon. Finally, it is proposed that the displacement of native grasslands may be bio-physico-chemically balanced by the introduction of crops, in relation to the silicon cycle, since they are also important silicophytolith producers in the SE Pampean agroecosystems. Acknowledgments: This work was supported by PICT 1583/2013 AGENCIA and EXA 741/15-UNMDP

Heavy Quark Spectroscopy and Matrix Elements: A Lattice Study using the Static Approximation

We present results of a lattice analysis of the $B$ parameter, $B_B$, the decay constant $f_B$, and several mass splittings using the static approximation. Results were obtained for 60 quenched gauge configurations computed at $\beta=6.2$ on a lattice size of $24^3\times48$. Light quark propagators were calculated using the $O(a)$-improved Sheikholeslami-Wohlert action. We find \Bbstat(m_b) = 0.69\er{3}{4} {\rm(stat)}\er{2}{1} {\rm(syst)}, corresponding to \Bbstat = 1.02\er{5}{6}\er{3}{2}, and \fbstat = 266\err{18}{20}\err{28}{27} \mev, f_{B_s}^2 B_{B_s}/f_B^2 B_B = 1.34\er{9}{8}\er{5}{3}, where a variational fitting technique was used to extract \fbstat. For the mass splittings we obtain M_{B_s}-M_{B_d} = 87\err{15}{12}\err{6}{12} \mev, M_{\Lambda_b}-M_{B_d} = 420\errr{100}{90}\err{30}{30} \mev and M_{B^*}^2-M_B^2 = 0.281\err{15}{16}\err{40}{37} \gev^2. We compare different smearing techniques intended to improve the signal/noise ratio. From a detailed assessment of systematic effects we conclude that the main systematic uncertainties are associated with the renormalisation constants relating a lattice matrix element to its continuum counterpart. The dependence of our findings on lattice artefacts is to be investigated in the future.Comment: 40 pages, uuencoded compressed tar file, containing one LaTeX file and 14 postscript files (to be included with epsf). Minor change in the value of the B parameter. Contains corrected value for the B*-B mass splitting. Version accepted for publication in Phys. Rev.

First Lattice Study of Semileptonic Decays of Lambda_b and Xi_b Baryons

We present the results of the first lattice study of semileptonic decays of baryons containing a b-quark. Predictions for the decay distributions are given and the Isgur-Wise functions for heavy baryons are computed, for values of the velocity transfer up to about omega=1.2. The computations are performed on a 24^3 x 48 lattice at beta=6.2 using the Sheikholeslami-Wohlert action in the quenched approximation.Comment: 55 pages, 17 ps figures, Latex 2.09, uses eps

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]