Mechanism of elastolysis by pancreatic elastase

Résumé Nous présentons une étude du mécanisme de l'élastolyse par une élastase partiellement purifiée du pancréas. La méthode utilisée consiste dans le dosage spectrophotométrique de l'«azoelastine» dissoute. Cette protéine n'est que très lentement hydrolysée par la trypsine et chymotrypsine cristallisées. L'élastase possède une activité protéasique considérable. L'enzyme est très rapidement adsorbée sur l'élastine. Après une incubation à pH 4,5 avec l'enzyme adsorbée, le temps de latence de l'élastolyse disparaît et la rapidité de la réaction devient proportionnelle à la concentration en élastase.     

Chemical modifications of cartilage matrix during endochondral calcification

Résumé On a étudié la composition chimique de différentes zones fonctionelles de la matrice du cartilage ossifiable scapulaire et costal. On a constaté qu'en s'approchant du front de calcification, le collagène diminue fortement tandis que les mucopolysaccarides et les protéines non collagènes augmentent.

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This investigation was supported by grants from the Italian National Research Council.     

Genome sequencing in microfabricated high-density picolitre reactors

The proliferation of large-scale DNA-sequencing projects in recent years has driven a search for alternative methods to reduce time and cost. Here we describe a scalable, highly parallel sequencing system with raw throughput significantly greater than that of state-of-the-art capillary electrophoresis instruments. The apparatus uses a novel fibre-optic slide of individual wells and is able to sequence 25 million bases, at 99% or better accuracy, in one four-hour run. To achieve an approximately 100-fold increase in throughput over current Sanger sequencing technology, we have developed an emulsion method for DNA amplification and an instrument for sequencing by synthesis using a pyrosequencing protocol optimized for solid support and picolitre-scale volumes. Here we show the utility, throughput, accuracy and robustness of this system by shotgun sequencing and de novo assembly of the Mycoplasma genitalium genome with 96% coverage at 99.96% accuracy in one run of the machine.     

Evidence from the Mars Express High Resolution Stereo Camera for a frozen sea close to Mars' equator

It is thought that the Cerberus Fossae fissures on Mars were the source of both lava and water floods two to ten million years ago. Evidence for the resulting lava plains has been identified in eastern Elysium, but seas and lakes from these fissures and previous water flooding events were presumed to have evaporated and sublimed away. Here we present High Resolution Stereo Camera images from the European Space Agency Mars Express spacecraft that indicate that such lakes may still exist. We infer that the evidence is consistent with a frozen body of water, with surface pack-ice, around 5 degrees north latitude and 150 degrees east longitude in southern Elysium. The frozen lake measures about 800 x 900 km in lateral extent and may be up to 45 metres deep--similar in size and depth to the North Sea. From crater counts, we determined its age to be 5 +/- 2 million years old. If our interpretation is confirmed, this is a place that might preserve evidence of primitive life, if it has ever developed on Mars.     

Neon isotopes constrain convection and volatile origin in the Earth's mantle

Identifying the origin of primordial volatiles in the Earth's mantle provides a critical test between models that advocate magma-ocean equilibration with an early massive solar-nebula atmosphere and those that require subduction of volatiles implanted in late accreting material. Here we show that neon isotopes in the convecting mantle, resolved in magmatic CO2 well gases, are consistent with a volatile source related to solar corpuscular irradiation of accreting material. This contrasts with recent results that indicated a solar-nebula origin for neon in mantle plume material, which is thought to be sampling the deep mantle. Neon isotope heterogeneity in different mantle sources suggests that models in which the plume source supplies the convecting mantle with its volatile inventory require revision. Although higher than accepted noble gas concentrations in the convecting mantle may reduce the need for a deep mantle volatile flux, any such flux must be dominated by the neon (and helium) isotopic signature of late accreting material.