Three-dimensional stochastic model of actin–myosin binding in the sarcomere lattice

The effect of molecule tethering in three-dimensional (3-D) space on bimolecular binding kinetics is rarely addressed and only occasionally incorporated into models of cell motility. The simplest system that can quantitatively determine this effect is the 3-D sarcomere lattice of the striated muscle, where tethered myosin in thick filaments can only bind to a relatively small number of available sites on the actin filament, positioned within a limited range of thermal movement of the myosin head. Here we implement spatially explicit actomyosin interactions into the multiscale Monte Carlo platform MUSICO, specifically defining how geometrical constraints on tethered myosins can modulate state transition rates in the actomyosin cycle. The simulations provide the distribution of myosin bound to sites on actin, ensure conservation of the number of interacting myosins and actin monomers, and most importantly, the departure in behavior of tethered myosin molecules from unconstrained myosin interactions with actin. In addition, MUSICO determines the number of cross-bridges in each actomyosin cycle state, the force and number of attached cross-bridges per myosin filament, the range of cross-bridge forces and accounts for energy consumption. At the macroscopic scale, MUSICO simulations show large differences in predicted force-velocity curves and in the response during early force recovery phase after a step change in length comparing to the two simplest mass action kinetic models. The origin of these differences is rooted in the different fluxes of myosin binding and corresponding instantaneous cross-bridge distributions and quantitatively reflects a major flaw of the mathematical description in all mass action kinetic models. Consequently, this new approach shows that accurate recapitulation of experimental data requires significantly different binding rates, number of actomyosin states, and cross-bridge elasticity than typically used in mass action kinetic models to correctly describe the biochemical reactions of tethered molecules and their interaction energetics

Tracker Operation and Performance at the Magnet Test and Cosmic Challenge

During summer 2006 a fraction of the CMS silicon strip tracker was operated in a comprehensive slice test called the Magnet Test and Cosmic Challenge (MTCC). At the MTCC, cosmic rays detected in the muon chambers were used to trigger the readout of all CMS sub-detectors in the general data acquisition system and in the presence of the 4 T magnetic field produced by the CMS superconducting solenoid. This document describes the operation of the Tracker hardware and software prior, during and after data taking. The performance of the detector as resulting from the MTCC data analysis is also presented

Anti-TNF- therapy prevents the recurrence of joint bleeding in haemophilia and arthritis

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The conformation of myosin head domains in rigor muscle determined by X-ray interference.

In the absence of adenosine triphosphate, the head domains of myosin cross-bridges in muscle bind to actin filaments in a rigor conformation that is expected to mimic that following the working stroke during active contraction. We used x-ray interference between the two head arrays in opposite halves of each myosin filament to determine the rigor head conformation in single fibers from frog skeletal muscle. During isometric contraction (force T-0), the interference effect splits the M3 x-ray reflection from the axial repeat of the heads into two peaks with relative intensity (higher angle/lower angle peak) 0.76. In demembranated fibers in rigor at low force

Performance studies of the CMS strip tracker before installation

Peer reviewe

Tracker Operation and Performance at the Magnet Test and Cosmic Challenge

During summer 2006 a fraction of the CMS silicon strip tracker was operated in a comprehensive slice test called the Magnet Test and Cosmic Challenge (MTCC). At the MTCC, cosmic rays detected in the muon chambers were used to trigger the readout of all CMS sub-detectors in the general data acquisition system and in the presence of the 4 T magnetic field produced by the CMS superconducting solenoid. This document describes the operation of the Tracker hardware and software prior, during and after data taking. The performance of the detector as resulting from the MTCC data analysis is also presented

Aportes de la huerta escolar agroecológica al aprendizaje de niñas y niños en escuelas de Montevideo, a través del Programa Huertas en Centros Educativos

Huertas escolares agroecológicas son herramientas que apuntan a generar múltiples aprendizajes. El Programa Huertas en Centros Educativos es una experiencia que desarrollan la Intendencia de Montevideo, la Administración Nacional de Enseñanza Pública y la Universidad de la República, desde el año 2005. Desarrolla huertas en 53 escuelas primarias. Trabajan en él, 32 orientadores de huerta, con 15.000 niños y 500 maestros, vinculando la huerta a las actividades curriculares. El objetivo general es promover un cambio cultural hacia una nueva forma de dignificar a la persona, en relación con la naturaleza. Busca facilitar aprendizajes curiculares, desarrollar hábitos de trabajo y de alimentación saludable, prácticas agroecológicas y que las mismas lleguen a los hogares. El presente trabajo sistematiza información publicada por el PHCE, tomando como eje los aprendizajes que facilita esta herramienta educativa. Se concluye que la huerta escolar agroecológica es una excelente herramienta pedagógica, facilitando el aprendizaje de contenidos curriculares, el desarrollo de valores y actitudes para la integración social y la educación alimentaria.Agroecological school gardens are tools aimed at generating multiple learning. The school gardening program (PHCE) is an experience that has been developing by Montevideo's local government, the National Administration of Public Education and the University of the Republic, since 2005. It develops orchards in 53 elementary schools. 32 orchard counselors work with 15.000 children and 500 teachers, linking the garden to their curricular activities. The overall objective is to promote a cultural change towards a new form of dignity to the person in connection with nature. The program seeks to facilitate learning, develop work and healthy eating habits, ecological practices and that they reach homes. This paper organizes information published by the PHCE, focusing on the teaching that this educational tool can leave. It is concluded that the agroecological school garden is an excellent educational tool, providing curricular content and development of values and attitudes toward social integration and food and nutrition education.Eje A5: Sistemas de conocimientoFacultad de Ciencias Agrarias y Forestale