gamma-zein secondary structure in solution by circular dichroism

The proline-rich N-terminal domain of gamma-zein has been reported in relevant process, which include its ability to cross the cell membranes. Evidences indicate that synthetic hexapeptide (PPPVHL), naturally found in N-terminal portion of gamma-zein, can adopt the polyproline II (PPII) conformation in aqueous solution. The secondary structure of gamma-zein in maize protein bodies had been analyzed by solid state Fourier transform infrared and nuclear magnetic resonance spectroscopies. However, it was not possible to measure PPII content in physiological environment since the beta-sheet and PPII signals overlap in both solid state techniques. Here, the secondary structure of gamma-zein has been analyzed by circular dichroism in SDS aqueous solution with and without ditiothreitol (DTT), and in 60% of 2-propanol and water with DTT The results show that gamma-zein has high helical content in all solutions. The PPII conformation was present at about 7% only in water/DTT solution. (c) 2007 Wiley Periodicals, Inc.

Conformational Properties of Angiotensin II and Its Active and Inactive TOAC-Labeled Analogs in the Presence of Micelles. Electron Paramagnetic Resonance, Fluorescence, and Circular Dichroism Studies

The interaction between angiotensin II (AII, DRVYIHPF) and its analogs carrying 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC) and detergents-negatively charged sodium dodecyl sulfate (SDS) and zwitterionic N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS)-was examined by means of EPR, CD, and fluorescence. EPR spectra of partially active TOAC(1)-AII and inactive TOAC(3)-AII in aqueous solution indicated fast tumbling, the freedom of motion being greater at the N-terminus. Line broadening occurred upon interaction with micelles. Below SDS critical micelle concentration, broader lines indicated complex formation with tighter molecular packing than in micelles. Small changes in hyperfine splittings evinced TOAC location at the micelle-water interface. The interaction with anionic micelles was more effective than with zwitterionic micelles. Peptide-micelle interaction caused fluorescence increase. The TOAC-promoted intramolecular fluorescence quenching was more, pronounced for TOAC(3)-AII because of the proximity between the nitroxide and Tyr(4). CD spectra showed that although both AII and TOAC(1)-AII presented flexible conformations in water, TOAC(3)-AII displayed conformational restriction because of the TOAC-imposed bend (Schreier et al., Biopolymers 2004, 74, 389). In HPS, conformational changes were observed for the labeled peptides at neutral and basic pH. In SDS, all peptides underwent pH-dependent conformational changes. Although the spectra suggested similar folds for All and TOAC(1)-AII, different conformations were acquired by TOAC(3)-AII. The membrane environment has been hypothesized to shift conformational equilibria so as to stabilize the receptor-bound conformation of ligands. The fact that TOAC(3)-AII is unable to acquire conformations similar to those of native AII and partially active TOAC(1)-AII is probably the explanation for its lack of biological activity. (C) 2009 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 92: 525-537, 2009.

Single-mode acceleration of matter waves in circular waveguides

Ultracold gases in ring geometries hold promise for significant improvements of gyroscopic sensitivity. Recent experiments have realized atomic and molecular storage rings with radii in the centimeter range, sizes whose practical use in inertial sensors requires velocities significantly in excess of typical recoil velocities. We use a combination of analytical and numerical techniques to study the coherent acceleration of matter waves in circular waveguides, with particular emphasis on its impact on single-mode propagation. In the simplest case we find that single-mode propagation is best maintained by the application of time-dependent acceleration force with the temporal profile of a Blackmann pulse. We also assess the impact of classical noise on the acceleration process.

Thomas-Fermi ground state of dipolar fermions in a circular storage ring

Recent developments in the field of ultracold gases has led to the production of degenerate samples of polar molecules. These have large static electric-dipole moments, which in turn causes the molecules to interact strongly. We investigate the interaction of polar particles in waveguide geometries subject to an applied polarizing field. For circular waveguides, tilting the direction of the polarizing field creates a periodic inhomogeneity of the interparticle interaction. We explore the consequences of geometry and interaction for stability of the ground state within the Thomas-Fermi model. Certain combinations of tilt angles and interaction strengths are found to preclude the existence of a stable Thomas-Fermi ground state. The system is shown to exhibit different behavior for quasi-one-dimensional and three-dimensional trapping geometries.

O papel dos valores e crenças africanas no tempo de trabalho circular, nas estratégias, na negociação das diferenças entre operários e dirigentes no corredor de Maputo

A categoria tempo circular ou indiferenciado mostra que o trabalho formal é vivido de acordo com a subjetividade dos seus participantes, com uma multiplicidade de significados e de configurações sempre variáveis. Neste estudo, identificou-se a existência de uma relação entre o tempo circular e as estratégias elaboradas pelos trabalhadores na conquista de uma maior autonomia nos espaços de trabalho. Além disso, observou-se a convivência entre trabalhadores, empresários e dirigentes governamentais e sindicais presentes num projeto de modernização no sul de Moçambique, denominado Corredor de Desenvolvimento de Maputo e constatou-se o modo como é realizada a negociação das diferenças. Realizou-se um levantamento das principais estratégias levadas a cabo por empresários nacionais, estrangeiros, governo e sindicatos na gestão da força de trabalho, formação, qualificação e o uso do tempo nos espaços de trabalho, bem como as perspectivas de desenvolvimento humano trazido por este projeto na região de Maputo. Por enquanto, ainda não foi possível detectar um interesse real dos grupos empresariais e governamentais em delinear caminhos tendentes a encontrar equilíbrios possíveis entre a modernização e a tradição, que sejam compatíveis com a satisfação das necessidades, valores e crenças e o respeito ao imaginário dos grupos envolvidos na construção da modernização tecnológica do país. Parecem evidentes estratégias em que a responsabilidade social está ausente e a estratégia de abertura das Zonas Francas Industriais ao investimento externo carece de uma verdadeira negociação entre “parceiros” em que sejam distribuídas de forma equitativa as vantagens e desvantagens inerentes aos projetos de industrialização a serem implantados localmente. Os testemunhos obtidos junto dos protagonistas moçambicanos expressaram uma grande frustração e desencantamento quanto a resultados que possam vir a ser promissores para as populações, trabalhadores e empresários nacionais do projeto em curso. Portanto, este projeto mostra ser um processo exógeno introduzido à revelia de seus principais protagonistas nesta fase de implantação em território moçambicano e onde os aspectos culturais foram desrespeitados, além de serem usados como estratégia para tirar vantagens adicionais.

Análise experimental do sistema "vórtice ferradura" no escoamento ao redor de um cilindro circular

Este trabalho apresenta o estudo de um sistema hidrodinâmico encontrada em muitas situações dentro da mecânica dos fluidos: o Vórtice Ferradura. Esta estrutura possui características bastante complexas e seu comportamento ainda é pouco compreendido e explicado. Assim, o escoamento ao redor do cilindro circular, em leito fixo, foi investigado experimentalmente, com o propósito de tentar caracterizar o comportamento hidrodinâmico do Vórtice Ferradura através da visualização de escoamento e medições de pressão. Para o trabalho, um cilindro foi montado. As visualizações do Vórtice foram feitas através de uma janela de visualização na seção de testes do canal. A filmagem foi feita através de uma câmera de vídeo VHS, de uso doméstico, e injeção de corante. As medições de pressão foram feitas através do emprego de transdutores de pressão, e divididas em dois grupos: (i) medições de pressão feitas no leito do canal, na linha de simetria, na região de escoamento próxima ao Vórtice; (ii) medições de pressão do escoamento na superfície do cilindro. As imagens, assim como os dados de transdutor, foram transportados para o meio digital para posterior manipulação e análise. Os resultados confirmam algumas descrições fornecidas pela literatura, bem como, também levantam algumas considerações sobre o assunto: as imagens permitiram a visualização das etapas de formação do Vórtice, descrever modificações em seu diâmetro ao longo dos ensaios, reconhecer a variabilidade espacial de sua posição e detectar a presença de um vórtice secundário. Os dados de transdutor descreveram o campo de pressões no leito do canal, modificado pela presença do cilindro e, ao redor da superfície do mesmo, bem como, o comportamento das flutuações de pressão, correlações, autocorrelações e espectros das flutuações de pressão dos transdutores, para estas situações.

Memória de um tempo circular no território de Carlos Fuentes

Ao contrário da concepção linear do pensamento ocidental, o tempo mexicano, situado na tradição pré-hispânica, indica uma multiplicidade de tempos, possibilitando que variadas e distantes épocas sejam realidades presentes. Nesse enfoque, diferentes tempos da história mexicana incorporam a narrativa de Carlos Fuentes, onde é comum passado, presente e futuro estarem imbricados em circularidades que resgatam com a imaginação e a linguagem uma memória encoberta pelo discurso totalizador. Na sua obra, Carlos Fuentes percorre mitos, tempos e espaços através de uma escritura que traduz uma cultura mestiça construída por vertentes americanas e européias. No entrelaçamento da pluralidade dos mundos, descobre os acontecimentos do passado, introduzindo significações aos silêncios relegados à margem da história. Através das análises de “Las dos orillas” – conto do livro El naranjo; do romance La muerte de Artemio Cruz e de personagens que transitam nos contos de La frontera de cristal, são investigados três momentos da história mexicana: Conquista espanhola, Revolução mexicana e migrações da atualidade na fronteira. Desse modo, são exploradas possibilidades históricas disseminadas na produção de Carlos Fuentes

Ampliação de movimentos na dança circular com pessoas com deficiência visual

This paper aims at studying how circular dance can afford to sight-disabled peoples movement and how they can learn to cope with the deep movement of relation, consciousness, appropriation and communion with the world. Inside circular dance, a cosmic metaphor, is inscribed the movement of the world, which tells and changes amorously the human history. In the works of Paulo Freire and Maurice Merleau-Ponty one can find the necessary support to discuss, as long as possible, movement and existence. Research-action is used as a methodological approach whose empirical center is placed on the Institute of Education and Rehabilitation of Blind, in Natal, which shelters eight sightdisabled adults. The research s data reveal that the practice of circular dance concurs to enlarge the movement of the research s subjects, to develop a more accurate perception of their selves and of their own capacities, as well as improve the relations Me/Others, Me/World, which require a context of differences. The study has revealed that the practice of dance develops a better perception of the limits and surpasses as a human condition and, in consequence, the discovery of one s own body and the other s body as a resource of lessons and representations of the self and of the world. It lets out the development of a new way of thinking and coping with discrimination surrounding the disabled persons. In movement, in circular dance, the barrier between sight disablement and vision loses force.

Antenas monopolo planar com patch em anel circular para sistemas UWB

The microstrip antennas are largely used in wireless communication systems due to their low cost, weight, less complex construction and manufacturing, in addition to its versatility. UWB systems have emerged as an alternative to wireless communications over short distances because they offer of higher capacity and lower multipath distortion than other systems with the same purpose. Combining the advantages of microstrip antennas to the characteristics of UWB, it is possible to develop more and more smaller devices, with diverse geometries to operate satisfactorily in these systems. This paper aims to propose alternatives to microstrip antennas for UWB systems operate in the range between 3.1 and 10.6 GHz, with a patch on circular ring. Some techniques are analyzed and employed to increase the bandwidth of proposed antenna: the insertion of a parasitic elements and a rectangular slit in the displaced ground plane. For this, key issues are presented as the basic principles of UWB systems, the fundamental theory of antennas and microstrip antennas. The simulations and experimental characterization of constructed antennas are presented, as well as analysis of parameters such as bandwidth and radiation pattern

Expression, purification, and circular dichroism analysis of human CDK9

The human cyclin-dependent kinase 9 (CDK9) protein was expressed in E coli BL21 using the pET23a vector at 30 degrees C. Several milligrams of protein were purified from soluble fraction using ionic exchange and ATP-affinity chromatography. The structural quality of recombinant CDK9 and the estimation of its secondary structure were obtained by circular dichroism. Structural models of CDK9 presented 26% of helices in agreement with the spectra by circular dichroism analysis. This is the first report on human CDK9 expression in Escherichia coli and structure analysis and provides the first step for the development of CDK9 inhibitors. (c) 2006 Elsevier B.V. All rights reserved.

Superconducting boundary conditions for mesoscopic circular samples

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Temperature-dependent vortex matter in a superconducting mesoscopic circular sector

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vortices in a mesoscopic superconducting circular sector

In the present paper we develop an algorithm to solve the time dependent Ginzburg-Landau equations, by using the link variables technique, for circular geometries. In addition, we evaluate the Helmholtz and Gibbs free energy, the magnetization, and the number of vortices. This algorithm is applied to a circular sector. We evaluate the superconduting-normal magnetic field transition, the magnetization, and the superconducting density. Our results point out that, as we reduce the superconducting area, the nucleation field increases. Nevertheless, as the angular width of the circular sector goes to small values the asymptotic behavior is independent of the sample area. We also show that the value of the first nucleation field is approximately the same independently of the form of the circular sector. Furthermore, we study the nucleation of giant and multivortex states for the different shapes of the present geometry.

Low-altitude, near-polar and near-circular orbits around Europa

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Treatment of segmental tibial defects using acute bone shortening followed by gradual lengthening with circular external fixator

The aim of this study was to clinically and radiographically evaluate acute bone shortening followed by gradual lengthening in the treatment of large segmental tibia defects induced in seven clinically normal dogs. A circular external fixator was assembled with one proximal 5/8-circle ring, one middle ring and one distal ring connected with three rods. Thirty per cent of the tibia and fibula were removed in the middle and distal parts of the diaphyses, between the middle and distal rings. Acute bone shortening with compression of proximal and distal segments was performed. A subperiosteal osteotomy was performed between the half-ring and middle ring. Bone distraction started 7 days after surgery; after lengthening, the apparatus was left in place for 14 weeks for consolidation of regenerated bone. The frame was removed at the end of this period, and the dogs observed for four more weeks. Functional results were considered excellent in two, good in three and fair in the other two dogs. Bone regeneration within the distraction gap was obtained 14 weeks after neutral fixation period. We concluded that acute bone shortening followed by gradual lengthening by Ilizarov method can be used to treat extensive tibial defects in dogs, although it presents limb temporary abnormal limb shape and unequal length as early disadvantages.