From Collapse to Freezing in Random Heteropolymers

We consider a two-letter self-avoiding (square) lattice heteropolymer model of N_H (out ofN) attracting sites. At zero temperature, permanent links are formed leading to collapse structures for any fraction rho_H=N_H/N. The average chain size scales as R = N^{1/d}F(rho_H) (d is space dimension). As rho_H --> 0, F(rho_H) ~ rho_H^z with z={1/d-nu}=-1/4 for d=2. Moreover, for 0 < rho_H < 1, entropy approaches zero as N --> infty (being finite for a homopolymer). An abrupt decrease in entropy occurs at the phase boundary between the swollen (R ~ N^nu) and collapsed region. Scaling arguments predict different regimes depending on the ensemble of crosslinks. Some implications to the protein folding problem are discussed.Comment: 4 pages, Revtex, figs upon request. New interpretation and emphasis. Submitted to Europhys.Let

Fine Selmer Groups and Isogeny Invariance

We investigate fine Selmer groups for elliptic curves and for Galois representations over a number field. More specifically, we discuss Conjecture A, which states that the fine Selmer group of an elliptic curve over the cyclotomic extension is a finitely generated $\mathbb{Z}_p$-module. The relationship between this conjecture and Iwasawa's classical $\mu=0$ conjecture is clarified. We also present some partial results towards the question whether Conjecture A is invariant under isogenies.Comment: 20 page

Sequential NMR assignments of labile protons in DNA using two-dimensional nuclear-overhauser-enhancemnt spectroscopy with three jump-and-return pulse sequences

Two-dimensional nuclear Overhauser enhancement (NOESY) spectra of labile protons were recorded in H2O solutions of a protein and of a DNA duplex, using a modification of the standard NOESY experiment with all three 90&#176; pulses replaced by jump-and-return sequences. For the protein as well as the DNA fragment the strategically important spectral regions could be recorded with good sensitivity and free of artifacts. Using this procedure, sequence-specific assignments were obtained for the imino protons, C2H of adenine, and C4NH2 of cytosine in a 23-base-pair DNA duplex which includes the 17-base-pair OR3 repressor binding site of bacteriophage &#955;. Based on comparison with previously published results on the isolated OR3 binding site, these data were used for a study of chain termination effects on the chemical shifts of imino proton resonances of DNA duplexes

Novel strategies to enhance vaccine immunity against coccidioidomycosis

Coccidioidomycosis is a potentially life-threatening respiratory mycosis endemic to the Americas and caused by inhalation of spores produced by the molds Coccidioides immitis and C. posadasii

Synthesis and structural characterization of a mimetic membrane-anchored prion protein

During pathogenesis of transmissible spongiform encephalopathies (TSEs) an abnormal form (PrPSc) of the host encoded prion protein (PrPC) accumulates in insoluble fibrils and plaques. The two forms of PrP appear to have identical covalent structures, but differ in secondary and tertiary structure. Both PrPC and PrPSc have glycosylphospatidylinositol (GPI) anchors through which the protein is tethered to cell membranes. Membrane attachment has been suggested to play a role in the conversion of PrPC to PrPSc, but the majority of in vitro studies of the function, structure, folding and stability of PrP use recombinant protein lacking the GPI anchor. In order to study the effects of membranes on the structure of PrP, we synthesized a GPI anchor mimetic (GPIm), which we have covalently coupled to a genetically engineered cysteine residue at the C-terminus of recombinant PrP. The lipid anchor places the protein at the same distance from the membrane as does the naturally occurring GPI anchor. We demonstrate that PrP coupled to GPIm (PrP-GPIm) inserts into model lipid membranes and that structural information can be obtained from this membrane-anchored PrP. We show that the structure of PrP-GPIm reconstituted in phosphatidylcholine and raft membranes resembles that of PrP, without a GPI anchor, in solution. The results provide experimental evidence in support of previous suggestions that NMR structures of soluble, anchor-free forms of PrP represent the structure of cellular, membrane-anchored PrP. The availability of a lipid-anchored construct of PrP provides a unique model to investigate the effects of different lipid environments on the structure and conversion mechanisms of PrP

T helper cell subsets specific for pseudomonas aeruginosa in healthy individuals and patients with cystic fibrosis

Background: We set out to determine the magnitude of antigen-specific memory T helper cell responses to Pseudomonas aeruginosa in healthy humans and patients with cystic fibrosis. Methods: Peripheral blood human memory CD4+ T cells were co-cultured with dendritic cells that had been infected with different strains of Pseudomonas aeruginosa. The T helper response was determined by measuring proliferation, immunoassay of cytokine output, and immunostaining of intracellular cytokines. Results: Healthy individuals and patients with cystic fibrosis had robust antigen-specific memory CD4+ T cell responses to Pseudomonas aeruginosa that not only contained a Th1 and Th17 component but also Th22 cells. In contrast to previous descriptions of human Th22 cells, these Pseudomonal-specific Th22 cells lacked the skin homing markers CCR4 or CCR10, although were CCR6+. Healthy individuals and patients with cystic fibrosis had similar levels of Th22 cells, but the patient group had significantly fewer Th17 cells in peripheral blood. Conclusions: Th22 cells specific to Pseudomonas aeruginosa are induced in both healthy individuals and patients with cystic fibrosis. Along with Th17 cells, they may play an important role in the pulmonary response to this microbe in patients with cystic fibrosis and other conditions

Aspectos económicos y ambientales de la producción de hidrógeno en la provincia de Córdoba, a partir de recursos eólicos

En este trabajo se presenta la Evaluación Económica y Ambiental del proyecto de instalación de un parque eólico en la provincia de Córdoba con fines de producción de hidrógeno. El potencial de hidrógeno eólico se analiza para cada departamento de la provincia, considerando los requerimientos energéticos del electrolizador y el factor de capacidad de los sitios analizados. Se analizaron cuatro aspectos del sistema: la evaluación del recurso eólico, el análisis del costo de producción de hidrógeno vía electrólisis, los requerimientos de energía eólica anual para producir hidrógeno y la evaluación de impacto ambiental del proyecto. Para ello se modela una planta que genera una potencia nominal de 60 MW. A partir del costo modelado de producción de la energía, se determina el de producción de hidrógeno. El presente análisis contribuirá a definir los desafíos y oportunidades para la producción de hidrógeno/eólico, que definirán una futura economía del hidrógeno.This paper presents the Economic and Environmental Project evaluation for installation of a wind farm in the province of Cordoba for the purpose of hydrogen production. The potential of hydrogen wind is analyzed for each department province, considering the energy requirements of the electrolyzer and the capacity factor of samples analyzed. We analyzed four aspects of system: hydrogen resource assessment, cost analysis of hydrogen production via electrolysis, wind energy requirements to produce hydrogen and annual assessment project's environmental impact. For this purpose a plant that generates a nominal power of 60 MW was modeled. From a model of cost production of energy the cost production of hydrogen was determined. This analysis should help to define the challenges and opportunities for the production of hydrogen / wind, defining a future hydrogen economy.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Aspectos económicos y ambientales de la producción de hidrógeno en la provincia de Córdoba, a partir de recursos eólicos

En este trabajo se presenta la Evaluación Económica y Ambiental del proyecto de instalación de un parque eólico en la provincia de Córdoba con fines de producción de hidrógeno. El potencial de hidrógeno eólico se analiza para cada departamento de la provincia, considerando los requerimientos energéticos del electrolizador y el factor de capacidad de los sitios analizados. Se analizaron cuatro aspectos del sistema: la evaluación del recurso eólico, el análisis del costo de producción de hidrógeno vía electrólisis, los requerimientos de energía eólica anual para producir hidrógeno y la evaluación de impacto ambiental del proyecto. Para ello se modela una planta que genera una potencia nominal de 60 MW. A partir del costo modelado de producción de la energía, se determina el de producción de hidrógeno. El presente análisis contribuirá a definir los desafíos y oportunidades para la producción de hidrógeno/eólico, que definirán una futura economía del hidrógeno.This paper presents the Economic and Environmental Project evaluation for installation of a wind farm in the province of Cordoba for the purpose of hydrogen production. The potential of hydrogen wind is analyzed for each department province, considering the energy requirements of the electrolyzer and the capacity factor of samples analyzed. We analyzed four aspects of system: hydrogen resource assessment, cost analysis of hydrogen production via electrolysis, wind energy requirements to produce hydrogen and annual assessment project's environmental impact. For this purpose a plant that generates a nominal power of 60 MW was modeled. From a model of cost production of energy the cost production of hydrogen was determined. This analysis should help to define the challenges and opportunities for the production of hydrogen / wind, defining a future hydrogen economy.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES