Determination of peptide topology through time-resolved double-resonance under electron capture dissociation conditions

Characterizing the conformation of biomolecules by mass spectrometry still represents a challenge. With their knotted structure involving a N-terminal macrolactam ring where the C-terminal tail of the peptide is threaded and sterically trapped, lasso peptides constitute an attractive model for developing methods for characterizing gas-phase conformation, through comparison with their unknotted topoisomers. Here, the kinetics of electron capture dissociation (ECD) of a lasso peptide, capistruin, was investigated by electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry and compared to that of its branched-cyclic topoisomer, lactam-capistruin. Both peptides produced rather similar ECD spectra but showed different extent of H(?) transfer from c(i)' to z(j)(?) ions. Time-resolved double-resonance experiments under ECD conditions were performed to measure the formation rate constants of typical product ions. Such experiments showed that certain product ions, in particular those related to H(?) transfer, proceeded through long-lived complexes for capistruin, while fast dissociation processes predominated for lactam-capistruin. The formation rate constants of specific ECD product ions enabled a clear differentiation of the lasso and branched-cyclic topoisomers. These results indicate that the formation kinetics of ECD product ions constitute a new way to explore the conformation of biomolecules and distinguish between topoisomers and, more generally, conformers.     

Radon measurement in schools located in three priority investigation areas in the province of Quebec, Canada

The purpose of this study was to measure radon concentration in public primary schools located in priority investigation areas, with the aim of decreasing occupants' exposure to radon in public buildings where concentrations exceed the Canadian Federal guidelines (i.e. 200 Bq m(-3)). In addition, the association between radon levels, substratum geological characteristics and schools' structural characteristics were investigated. The results showed that radon concentrations measured in the 65 investigated schools are generally below the Federal guideline levels. Eleven schools (17 %) had at least one measurement above the Federal guideline, while one had a level above 600 Bq m(-3). On average, targeted schools' occupants are exposed to radon concentrations of 56 Bq m(-3). Although statistical analysis, which was limited by the sample size, did not show any link between aggregated radon measurements and geochemical or radiological signatures of investigated sites, the geological evidence that led to the choice of the studied regions remains relevant.     

Etude par rayons x du diagramme plutonium-oxygene de la temperature ambiante jusqu'a 1100°c

With the help of a monochromatic X-ray diffraction technique (difficult to set up but providing good background attenuation and resolving power even for high specimen temperatures) it has been possible to establish several new features in the Pu-O phase diagram, such as a wide stability region for the α phase, a narrow (α + γ) phase region, a eutectoidal point at 670°C for an $\text{O}\text{Pu}$ ratio of 1.784 and several γ-type phases. Unfortunately, because of the complexity of the phases and the existence of metastable equilibria, we were unable to establish the details of the diagram for low oxygen contents, a region which all other investigators have also left in an imprecise condition.     

Mesure des effets de la propagation sur un faisceau hertzien numérique à 140 Mbit/s utilisant une modulation à huit états de phase

This paper presents the main field test results on a 140 Mbit/s digital radio system using eight phase shift keying. System performance, in terms of outage time and net fade margin, has been measured for various receiving configurations (space diversity, intermediate frequency slope equalizer).     

Kinetic and morphological study of digenite sulfidation into covellite

A kinetic and morphological study of Cu_2?xS sulfidation into CuS shows that the metal valency change occurs according to two different mechanisms : “external” growth similar to that in metals and precipitation from the metal vacancies supersaturated substrate. The diffusion step of (E = 19,7 ± 1 kcal.M^?1) within the covellite determines the transformation rate.     

Application des polynômes ultrasphériques pour les calculs et transformations de champs en zone proche des grandes ouvertures rayonnantes

Annals of Telecommunications - Cet article montre comment il est possible d’écrire l’intégrale de surface qui exprime le rayonnement d’un réflecteur ou de son...     

Heterodyne mixing experiments with NbN-based SIS junctions

Tests of niobium-nitride-based SIS junctions in our experimental receiver at ENS¹ have shown the remarkable stability in time and through thermal cycling of these high T_C material junctions; they were used to evaluate the real junction temperature in our vacuum cryogenerator. Results of heterodyne mixing experiments are presented at 100 GHz, showing that further progress in fabrication would be necessary. Detection experiments were performed at 460 GHz with encouraging results.     

Analysis of a 42·5 kb DNA sequence of chromosome X reveals three tRNA genes and 14 new open reading frames including a gene most probably belonging to the family of ubiquitin–protein ligases

We have sequenced a 42,500 bp stretch located on chromosome X of Saccharomyces cerevisiae between the genes MET3 and CDC8. This stretch contains 24 open reading frames (ORFs) of at least 100 amino acids. Ten of these correspond to previously published sequences, whereas of the 14 remaining ORFs, only one, GTD892, has significant similarity to proteins from yeast or other organisms. It may belong to the family of ubiquitin–protein ligases and be involved in the ubiquitin-dependent proteolytic pathway. In addition, three tRNA genes were recognized, two of which had not been hitherto localized. The sequence has been deposited in the Genome Sequence Data Base under Accession Number L36344.     

Fracture under compression: the direction of initiation

The preferential orientation for the initiation of a crack is the one which gives the maximum strain energy reduction for a given crack length. This proposed criterion is a logical extension of the maximum energy release rate criterion. It makes no assumptions on the configuration, the homogeneity, the stress condition on the crack faces, or the material response, consequently it is applicable to the usual engineering cases as well as to cases under compression and/or high confining pressures such as obtain inside the Earth. Numerical results for brittle materials (rocks) agree with laboratory and field data, and show that the criterion is an improvement over the empirical and approximate Coulomb-Mohr criterion which has been used for compressive fracture problems for more than 200 years. They also show that our method can be used in cases where it is not a priori evident whether the fracture will remain closed or will open.The mathematical formulation of the criterion is approached by way of constrained optimization, and the solution is proven to exist uniquely. The numerical implementation is based on a finite element scheme. An iterative method is employed to handle the material and geometric non-linearities.