866 research outputs found
Top-Down Mass Analysis of Protein Tyrosine Nitration: Comparison of Electron Capture Dissociation with “Slow-Heating” Tandem Mass Spectrometry Methods
Tyrosine nitration in proteins is an important post-translational modification (PTM) linked to various pathological conditions. When multiple potential sites of nitration exist, tandem mass spectrometry (MS/MS) methods provide unique tools to locate the nitro-tyrosine(s) precisely. Electron capture dissociation (ECD) is a powerful MS/MS method, different in its mechanisms to the “slow-heating” threshold fragmentation methods, such as collision-induced dissociation (CID) and infrared multiphoton dissociation (IRMPD). Generally, ECD provides more homogeneous cleavage of the protein backbone and preserves labile PTMs. However recent studies in our laboratory demonstrated that ECD of doubly charged nitrated peptides is inhibited by the large electron affinity of the nitro group, while CID efficiency remains unaffected by nitration. Here, we have investigated the efficiency of ECD versus CID and IRMPD for top-down MS/MS analysis of multiply charged intact nitrated protein ions of myoglobin, lysozyme, and cytochrome c in a commercial Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. CID and IRMPD produced more cleavages in the vicinity of the sites of nitration than ECD. However the total number of ECD fragments was greater than those from CID or IRMPD, and many ECD fragments contained the site(s) of nitration. We conclude that ECD can be used in the top-down analysis of nitrated proteins, but precise localization of the sites of nitration may require either of the “slow-heating” methods
A comprehensive set of plasmids for vanillate- and xylose-inducible gene expression in Caulobacter crescentus
Caulobacter crescentus is widely used as a powerful model system for the study of prokaryotic cell biology and development. Analysis of this organism is complicated by a limited selection of tools for genetic manipulation and inducible gene expression. This study reports the identification and functional characterization of a vanillate-regulated promoter (Pvan) which meets all requirements for application as a multi-purpose expression system in Caulobacter, thus complementing the established xylose-inducible system (Pxyl). Furthermore, we introduce a newly constructed set of integrating and replicating shuttle vectors that considerably facilitate cell biological and physiological studies in Caulobacter. Based on different narrow and broad-host range replicons, they offer a wide choice of promoters, resistance genes, and fusion partners for the construction of fluorescently or affinity-tagged proteins. Since many of these constructs are also suitable for use in other bacteria, this work provides a comprehensive collection of tools that will enrich many areas of microbiological research
Diseño de un estudio ergonĂłmico para evaluar patologĂas osteomusculares en puestos laborales. Estudio piloto
El propĂłsito de este estudio es la posibilidad de diseñar un estudio ergonĂłmico de los diferentes puestos de trabajo de una empresa, atendiendo a los de mayor significaciĂłn en cuanto a producir lesiones osteomusculares en los trabajadores, intentando valorar dichos puestos desde el punto de vista biomecánica, para evaluar el impacto de los movimientos y sobreesfuerzos realizados durante toda la jornada laboral y relacionarlos con los Ăndices de lesiones producidos en dichos trabajadores. Una vez realizado este estudio y si aporta valores significativos, se procederá a valorar las posibles soluciones y mejoras que se puedan implantar, siempre dentro de una viabilidad empresarial y posteriormente ver si dicha implantaciĂłn ha sido beneficiosa para la salud de los trabajadores
Dual-plate gold-gold microtrench electrodes for generator-collector voltammetry without supporting electrolyte
A gold-gold dual-plate microtrench electrode system based on two oppositely placed gold surfaces with 5 mm length, 17 μm average depth, and 6 μm inter-electrode gap is employed in generator-collector configuration in a four-electrode cell (counter electrode, reference electrode, and two independent working electrodes denoted “generator” – with scanning potential – and “collector” – with fixed potential). The dual-plate microtrench electrodes were investigated for (i) the reduction of Ru(NH3)6 3+, (ii) the oxidation of ferrocenemethanol, and (iii) the oxidation of iodide in aqueous media, all as a function of supporting electrolyte concentration. It is shown that due to the inter-electrode feedback character of the generator-collector currents, well-defined steady state sensor responses are obtained for the collector electrode even in the absence of added electrolyte. The variation in the mass transport limited steady state current (measured at the collector electrode) with addition/removal of supporting electrolyte remains low (compared to unexpectedly stronger effects caused by the switch between reduction and oxidation conditions at the collector electrode). Microtrench electrode systems are suggested for sensing applications without/with varying levels of supporting electrolyte.</p
Applicability of Milne-Eddington inversions to high spatial resolution observations of the quiet Sun
The physical conditions of the solar photosphere change on very small spatial
scales both horizontally and vertically. Such a complexity may pose a serious
obstacle to the accurate determination of solar magnetic fields. We examine the
applicability of Milne-Eddington (ME) inversions to high spatial resolution
observations of the quiet Sun. Our aim is to understand the connection between
the ME inferences and the actual stratifications of the atmospheric parameters.
We use magnetoconvection simulations of the solar surface to synthesize
asymmetric Stokes profiles such as those observed in the quiet Sun. We then
invert the profiles with the ME approximation. We perform an empirical analysis
of the heights of formation of ME measurements and analyze the uncertainties
brought about by the ME approximation. We also investigate the quality of the
fits and their relationship with the model stratifications. The atmospheric
parameters derived from ME inversions of high-spatial resolution profiles are
reasonably accurate and can be used for statistical analyses of solar magnetic
fields, even if the fit is not always good. We also show that the ME inferences
cannot be assigned to a specific atmospheric layer: different parameters sample
different ranges of optical depths, and even the same parameter may trace
different layers depending on the physical conditions of the atmosphere.
Despite this variability, ME inversions tend to probe deeper layers in granules
as compared with intergranular lanes.Comment: Accepted for publication in Astronomy and Astrophysic
Comparing linear and non linear wind flow models
Assessing wind conditions on complex terrain has become a hard task as terrain complexity increases. That is why there is a need to extrapolate in a reliable manner some wind parameters that determine wind farms viability such as annual average wind speed at all hub heights as well as turbulence intensities. The development of these tasks began in the early 90´s with the widely used linear model WAsP and WAsP Engineering especially designed for simple terrain with remarkable results on them but not so good on complex
orographies. Simultaneously non-linearized Navier Stokes solvers have been rapidly developed in the last decade through CFD (Computational Fluid Dynamics) codes allowing simulating atmospheric boundary layer flows over steep complex terrain more accurately reducing uncertainties.
This paper describes the features of these models by validating them through meteorological masts installed in a highly complex terrain. The study compares the results of the mentioned models in terms of wind speed and turbulence intensity
The history of a quiet-Sun magnetic element revealed by IMaX/SUNRISE
Isolated flux tubes are considered to be fundamental magnetic building blocks
of the solar photosphere. Their formation is usually attributed to the
concentration of magnetic field to kG strengths by the convective collapse
mechanism. However, the small size of the magnetic elements in quiet-Sun areas
has prevented this scenario from being studied in fully resolved structures.
Here we report on the formation and subsequent evolution of one such
photospheric magnetic flux tube, observed in the quiet Sun with unprecedented
spatial resolution (0\farcs 15 - 0\farcs 18) and high temporal cadence (33 s).
The observations were acquired by the Imaging Magnetograph Experiment (IMaX)
aboard the \textsc{Sunrise} balloon-borne solar observatory. The equipartition
field strength magnetic element is the result of the merging of several same
polarity magnetic flux patches, including a footpoint of a previously emerged
loop. The magnetic structure is then further intensified to kG field strengths
by convective collapse. The fine structure found within the flux concentration
reveals that the scenario is more complex than can be described by a thin flux
tube model with bright points and downflow plumes being established near the
edges of the kG magnetic feature. We also observe a daisy-like alignment of
surrounding granules and a long-lived inflow towards the magnetic feature.
After a subsequent weakening process, the field is again intensified to kG
strengths. The area of the magnetic feature is seen to change in anti-phase
with the field strength, while the brightness of the bright points and the
speed of the downflows varies in phase. We also find a relation between the
brightness of the bright point and the presence of upflows within it.Comment: 13 pages. Accepted in ApJ. Animation 1 can be viewed and downloaded
from: http://spg.iaa.es/downloads.as
Women as Key Agents in Sustainable Entrepreneurship: A Gender Multigroup Analysis of the SEO-Performance Relationship
Literature points out that the effect of sustainable entrepreneurship on firm performance may be contingent on internal factors, such as top manager characteristics. This paper proposes that the gender of a firm's chief executive officer (CEO) greatly influences the sustainable entrepreneurial orientation (SEO)-firm performance relationship. An empirical study was conducted on a stratified random sampling, collecting 210 questionnaires from top managers of firms in Valencia (Spain). A multigroup moderation analysis method was used. The results confirm that women tend to increase the positive effect of SEO in firm performance
- …