A Histidine Aspartate Ionic Lock Gates the Iron Passage in Miniferritins from Mycobacterium smegmatis

Background: DNA-binding protein from starved cells (Dps) are nano-compartments that can oxidize and store iron rendering protection from free radicals. Results: A histidine-aspartate ionic cluster in mycobaterial Dps2 modulates the rate of iron entry and exit in these proteins. Conclusion: Substitutions that disrupt the cluster interface alter the iron uptake/release properties with localized structural changes. Significance: Identifying important gating residues can help in designing nano-delivery vehicles. Dps (DNA-binding protein from starved cells) are dodecameric assemblies belonging to the ferritin family that can bind DNA, carry out ferroxidation, and store iron in their shells. The ferritin-like trimeric pore harbors the channel for the entry and exit of iron. By representing the structure of Dps as a network we have identified a charge-driven interface formed by a histidine aspartate cluster at the pore interface unique to Mycobacterium smegmatis Dps protein, MsDps2. Site-directed mutagenesis was employed to generate mutants to disrupt the charged interactions. Kinetics of iron uptake/release of the wild type and mutants were compared. Crystal structures were solved at a resolution of 1.8-2.2 for the various mutants to compare structural alterations vis a vis the wild type protein. The substitutions at the pore interface resulted in alterations in the side chain conformations leading to an overall weakening of the interface network, especially in cases of substitutions that alter the charge at the pore interface. Contrary to earlier findings where conserved aspartate residues were found crucial for iron release, we propose here that in the case of MsDps2, it is the interplay of negative-positive potentials at the pore that enables proper functioning of the protein. In similar studies in ferritins, negative and positive patches near the iron exit pore were found to be important in iron uptake/release kinetics. The unique ionic cluster in MsDps2 makes it a suitable candidate to act as nano-delivery vehicle, as these gated pores can be manipulated to exhibit conformations allowing for slow or fast rates of iron release.

Fabrication of self-aligned side gates to carbon nanotubes

We have fabricated self-aligned, side-gated suspended multi-walled carbon nanotubes (MWCNTs), with nanotube-to-gate spacing of less than 10 nm. Evaporated metal forms an island on a suspended MWCNT, the island and the nanotube act as a mask shielding the substrate, and lift-off then removes the metal island, leaving a set of self-aligned side gates. Al, Cr, Au, and Ti were investigated and the best results were obtained with Cr, at a yield of over 90%.

La matriculación de la primera abogada argentina : María Angélica Barreda

María Angélica Barreda, nacida en La Plata, el 16 de mayo de 1887, fue la primera abogada argentina. Estudió en la escuela normal, con la dirección de Mary Olstine Graham, quien había llegado al país desde Boston, convocada por Domingo F. Sarmiento. Mary O’Graham (1842-1903) no llegó a ver graduada a su ex alumna, ni tampoco a otras mujeres prestigiosas, como fueron la educadora Ada María Elflein, Josefina Passadori, conocida autora de textos escolares, o las escritoras Martha Mercader y Aurora Venturini, por citar solo algunas de las muchas egresadas de esa escuela, orgullo de los platenses.

História do movimento político, que no anno de 1842 teve lugar na provincia de Minas Geraes

José Antonio Marinho nasceu em Minas Gerais, em 1803, e morreu no Rio de Janeiro, em 1853. Em 1823, de passagem pela Bahia, envolveu-se nas lutas políticas daquele ano. Seguiu depois para Pernambuco, onde tomou parte, em 1824, na Confederação do Equador. Entrou para o Seminário de Olinda, mas denúncias de sua participação nos acontecimentos de 1824 impediram sua ordenação. Voltou, então, para Minas Gerais e conseguiu concluir sua formação sacerdotal. Ordenado em 1829, voltou às lides políticas, tornando-se advogado, jornalista e deputado provincial. Em 1836m elegeu-se deputado-geral por Minas Gerais, em 1842, tomou parte na Revolução Liberal, da qual foi primeiro historiador. Apesar de ter participado dos acontecimentos que historiou, tendo sido, por isso, acusado de parcial, o autor primou “pela verdade da exposição dos fatos”, como disse o Barão Homem de Melo. Com a autoridade de historiador da Revolução Liberal de 1842, Aluísio de Almeida afirmou que, sem a Historia do movimento politico, que no anno de 1842 teve lugar na Provincia de Minas Geraes, seria impossível escrever sobre aquele movimento. Obra rara, valorizada por treze litografias, que Aluísio de Almeida considera, com razão, “preciosas” : nove retratos, quatro vistas e uma planta, estas desdobradas. As litografias do primeiro volume se constituem de retratos do autor e de J. Feliciano, J. P. Dias de Carvalho e T. B. Ottoni, vistas da Praça de Barbacena, da Vila de Queluz e do Arraial da Lagoa Santa e planta do Arraial de Santa Luzia e suas imediações; e as do segundo volume de retratos de R. T. d’Aguiar, D.J. C. de Mendonça Franco, J. G. Teixeira de Carvalho, Diogo Antônio Feijó e Manuel Alves Branco e vista de Sabará.

Collecção das Leis do Imperio do Brasil de 1842

Parte 1 - Decisões

Collecção das Leis da Republica dos Estados Unidos do Brasil de 1921

Parte 1 - Atos do Poder Legislativo

Cartas enviadas por Ángel de Apraiz a Justo Garate entre 1921 y 1924

10 cartas (manuscritas y mecanografiadas) ; entre 335x227mm y 134x201mm. Ubicación: Caja 1 - Carpeta 33

Synopse dos trabalhos da Camara dos Srs. Deputados : relativos ao anno de 1921 : acompanhados de differentes documentos : organizada na Secretaria da mesma Camara

Sinopse dos trabalhos da Câmara dos Deputados, em 1921.

A new distributional record of Astropecten polyacanthus Muller and Troschel, 1842 (Echinodermata: Asteroidea) from the coastal waters of Pakistan

Previously an asteroid starfish Astropecten indicus has been described by Tahera (1996), and another species of the genus Astropecten i.e. A. polyacanthus Muller and Troschel, 1842 has been collected from the subtidal region of a sandy shore of Clifton (24°47'42"N 66°59'6"E), Karachi. The latter species is here reported for the first time from the Pakistan coast of the northern Arabian Sea and fills the gap in the known distribution. The species is briefly described and illustrated.

Electron-beam patterning of polymer electrolyte films to make multiple nanoscale gates for nanowire transistors

We report an electron-beam based method for the nanoscale patterning of the poly(ethylene oxide)/LiClO4 polymer electrolyte. We use the patterned polymer electrolyte as a high capacitance gate dielectric in single nanowire transistors and obtain subthreshold swings comparable to conventional metal/oxide wrap-gated nanowire transistors. Patterning eliminates gate/contact overlap, which reduces parasitic effects and enables multiple, independently controllable gates. The method's simplicity broadens the scope for using polymer electrolyte gating in studies of nanowires and other nanoscale devices. © 2013 American Chemical Society.

Highly electron transparent Graphene for field emission triode gates

The enhanced emission performance of a graphene/Mo hybrid gate electrode integrated into a nanocarbon field emission micro-triode electron source is presented. Highly electron transparent gate electrodes are fabricated from chemical vapor deposited bilayer graphene transferred to Mo grids with experimental and simulated data, showing that liberated electrons efficiently traverse multi-layer graphene membranes with transparencies in excess of 50-68%. The graphene hybrid gates are shown to reduce the gate driving voltage by 1.1 kV, whilst increasing the electron transmission efficiency of the gate electrode significantly. Integrated intensity maps show that the electron beam angular dispersion is dramatically improved (87.9°) coupled with a 63% reduction in beam diameter. Impressive temporal stability is noted (<1.0%) with surprising negligible long-term damage to the graphene. A 34% increase in triode perveance and an amplification factor 7.6 times that of conventional refractory metal grid gate electrode-based triodes are noted, thus demonstrating the excellent stability and suitability of graphene gates in micro-triode electron sources. A nanocarbon field emission triode with a hybrid gate electrode is developed. The graphene/Mo gate shows a high electron transparency (50-68%) which results in a reduced turn-on potential, increased beam collimation, reduced beam diameter (63%), enhanced stability (<1% variation), a 34% increase in perveance, and an amplification 7.6 times that of equivalent conventional refractory metal gate triodes. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.