Micro-Raman spectroscopy of plagioclase and maskelynite in Martian meteorites: Evidence of progressive shock metamorphism

We present the first systematic Micro-Raman spectroscopic investigation of plagioclase of different degree of shock metamorphism in Martian meteorites. The equilibrium shock pressure of all plagioclase phases of seventeen unpaired Martian meteorites was determined by measuring the shock-induced reduction of the refractive index. Systematic variations in the recorded Raman spectra of the plagioclase phases correlate with increasing shock pressure. In general, the shock induced deformation of the plagioclase crystal lattice leads to an increase of luminescence background and a broadening of all Raman bands. The most persistent bands are those at 505 and 590cm^(-1). For shock pressures above ～40GPa, the post shock temperature in the meteorites was high enough to initialise reordering of the O-tetrahedra in the structure of the diaplectic glass, leading to a decrease of intensity for the band near 590cm^(-1). At higher shock pressure (>45GPa) and post-shock temperature plagioclase starts to recrystallise. This results in a reduced luminescence background and a decrease of the full width of half maximum of the characteristic Raman bands

From the trap to the basket: getting to the bottom of the nuclear pore complex

Nuclear pore complexes (NPCs) are large supramolecular assemblies that perforate the double-membraned nuclear envelope and serve as the sole gateways of molecular exchange between the cytoplasm and the nucleus in interphase cells. Combining novel specimen preparation regimes with innovative use of high-resolution scanning electron microscopy, Hans Ris produced in the late eighties stereo images of the NPC with unparalleled clarity and structural detail, thereby setting new standards in the field. Since that time, efforts undertaken to resolve the molecular structure and architecture, and the numerous interactions that occur between NPC proteins (nucleoporins), soluble transport receptors, and the small GTPase Ran, have led to a deeper understanding of the functional role of NPCs in nucleocytoplasmic transport. In spite of these breakthroughs, getting to the bottom of the actual cargo translocation mechanism through the NPC remains elusive and controversial. Here, we review recent insights into NPC function by correlating structural findings with biochemical data. By introducing new experimental and computational results, we reexamine how NPCs can discriminate between receptor-mediated and passive cargo to promote vectorial translocation in a highly regulated manner. Moreover, we comment on the importance and potential benefits of identifying and experimenting with individual key components implicated in the translocation mechanism. We conclude by dwelling on questions that we feel are pertinent to a more rational understanding of the physical aspects governing NPC mechanics. Last but not least, we substantiate these uncertainties by boldly suggesting a new direction in NPC research as a means to verify such novel concepts, for example, a de novo designed ‘minimalist' NP

A Motivating Exploration on Lunar Craters and Low-Energy Dynamics in the Earth -- Moon System

It is known that most of the craters on the surface of the Moon were created by the collision of minor bodies of the Solar System. Main Belt Asteroids, which can approach the terrestrial planets as a consequence of different types of resonance, are actually the main responsible for this phenomenon. Our aim is to investigate the impact distributions on the lunar surface that low-energy dynamics can provide. As a first approximation, we exploit the hyberbolic invariant manifolds associated with the central invariant manifold around the equilibrium point L_2 of the Earth - Moon system within the framework of the Circular Restricted Three - Body Problem. Taking transit trajectories at several energy levels, we look for orbits intersecting the surface of the Moon and we attempt to define a relationship between longitude and latitude of arrival and lunar craters density. Then, we add the gravitational effect of the Sun by considering the Bicircular Restricted Four - Body Problem. As further exploration, we assume an uniform density of impact on the lunar surface, looking for the regions in the Earth - Moon neighbourhood these colliding trajectories have to come from. It turns out that low-energy ejecta originated from high-energy impacts are also responsible of the phenomenon we are considering.Comment: The paper is being published in Celestial Mechanics and Dynamical Astronomy, vol. 107 (2010

Augmented reality with tangible Auto-Fabricated models for molecular biology applications

Abstract: The evolving technology of computer auto-fabrication ("3-D printing") now makes it possible to produce physical models for complex biological molecules and assemblies. We report on an application that demonstrates the use of auto-fabricated tangible models and augmented reality for research and education in molecular biology, and for enhancing the scientific environment for collaboration and exploration. We have adapted an augmented reality system to allows virtual 3-D representations (generated by the Python Molecular Viewer) to be overlaid onto a tangible molecular model. Users can easily change the overlaid information, switching between different representations of the molecule, displays of molecular properties such as electrostatics, or dynamic information. The physical model provides a powerful, intuitive interface for manipulating the computer models, streamlining the interface between human intent, the physical model, and the computational activity. INTRODUCTION With the prevalence of structural and genomic data, molecular biology has become a human-guided, computer-assisted endeavor. The computer assists the essential human function in two ways: in exploration of scientific data, searching for and testing scientific hypotheses; and in collaboration between two or more scientists, to share knowledge and expertise. As databases grow, as our structure and process models become more complex, and as software methods become more diverse, access and manipulation of digital information is increasingly a critical issue for research in molecular biology. Currently, exploratory research in structural molecular biology is dominated by 3-D representations via computer graphics. Collaboration, both remote and local, is aided by shared viewing of these interactive visual representations of molecular data. Yet, recent advances in the field of human-computer interfaces have not been applied to the technology used by molecular biologists --most work in biomolecular structure and genomics is performed in front of a workstation using a mouse and keyboard as input devices. The tactile and kinesthetic senses provide key perceptual cues to our ability to understand 3-D form and to perform physical manipulations, but are currently under-utilized in molecular biology. Early structure research relied heavily on physical models: Pauling used his newly-invented spacefilling models to predict the basic folding units of protein structures [1] and Watson and Crick used brass-wire molecular models to help them determine the structure of DNA [2], which reconciled decades of genetic data. These researchers "thought with their hands" to produce important scientific results. Current research in molecular biology now focuses on larger assemblies and more complex interactions, for which traditional atomic models are inadequate. Merging physical and virtual objects into an "augmented reality" (AR) environment The evolving technology of computer auto-fabrication ("3D printing") now makes it possible to produce physical models for complex molecular assemblies. In this paper we report on an application that demonstrates the use of auto-fabricated tangible models and AR for research in molecular biology to enhance the scientific environment for collaboration and exploration. The physical models are integrated into an augmented reality environment to streamline the interface between human intent, the physical model, and the computational activity. We have developed an AR system that allows virtual 3-D representations generated by our Python Molecular Viewer (PMV) [5] to be overlaid on an auto-fabricated model of the molecule. The precise registration of the virtual objects with the real world is done using the ARToolKit library developed at the University of Washington We will first describe how we create 3D tangible models of a molecular structure from a known atomic structure, then explain the integration of ARToolKit in our Python framework, and finally present some examples. DESIGN OF PHYSICAL MODELS We use PMV October 10-15

Análise quali-quantitativa e espacial de poluição por microplástico ao longo da praia Tupi, Praia Grande – SP, Brasil: Quali-quantitative and spatial analysis of plastic pollution along praia Tupi, Praia Grande – SP, Brazil

A poluição marinha por plástico se tornou uma ameaça global para animais aquáticos e terrestres. Fragmentos desse material podem viajar pelas correntes oceânicas e chegar a lugares remotos ou parar no fundo dos oceanos, causando desequilíbrios aos ecossistemas e a vida. A magnitude desse problema serviu de inspiração para a realização do presente trabalho que buscou identificar a presença de pequenas partículas de plástico, denominadas micro e mesoplástico, e outros resíduos presentes na areia da Praia Tupi, no município de Praia Grande, em São Paulo. Foram coletadas amostras de areia em três faixas da praia com 30 metros de distância entre elas, sendo o início na face da praia (faixa mais próxima ao mar), na crista do berma (faixa intermediária entre o mar e a avenida) e no berma (mais próxima à avenida). As 21 amostras foram analisadas em laboratório com auxílio de uma peneira para identificação de pequenos fragmentos plásticos. No total foram encontrados 396 microplásticos, 51 mesoplásticos e 17 macroplásticos. A maior quantidade de microplásticos foi encontrada na face da praia, na linha da maré alta. Os macroplásticos concentraram-se no berma, onde há elevada concentração de visitantes. Dentre os microplásticos, 22 eram pellets, cuja presença indica que há fontes de resíduos que não sejam o turismo. Como resultado da ocorrência do plástico na praia foram identificados potenciais impactos ambientais, sociais e econômicos, alguns de caráter irreversível

The group II intron ribonucleoprotein precursor is a large, loosely packed structure

Group II self-splicing introns are phylogenetically diverse retroelements that are widely held to be the ancestors of spliceosomal introns and retrotransposons that insert into DNA. Folding of group II intron RNA is often guided by an intron-encoded protein to form a catalytically active ribonucleoprotein (RNP) complex that plays a key role in the activity of the intron. To date, possible structural differences between the intron RNP in its precursor and spliced forms remain unexplored. In this work, we have trapped the native Lactococcus lactis group II intron RNP complex in its precursor form, by deleting the adenosine nucleophile that initiates splicing. Sedimentation velocity, size-exclusion chromatography and cryo-electron microscopy provide the first glimpse of the intron RNP precursor as a large, loosely packed structure. The dimensions contrast with those of compact spliced introns, implying that the RNP undergoes a dramatic conformational change to achieve the catalytically active state