Solitary and repetitive binding motifs for the AP2 complex alpha-appendage in amphiphysin and other accessory proteins

Adaptor protein (AP) complexes bind to transmembrane proteins destined for internalization and to membrane lipids, so linking cargo to the accessory internalization machinery. This machinery interacts with the appendage domains of APs, which have platform and beta-sandwich subdomains, forming the binding surfaces for interacting proteins. Proteins that interact with the subdomains do so via short motifs, usually found in regions of low structural complexity of the interacting proteins. So far, up to four motifs have been identified that bind to and partially compete for at least two sites on each of the appendage domains of the AP2 complex. Motifs in individual accessory proteins, their sequential arrangement into motif domains, and partial competition for binding sites on the appendage domains coordinate the formation of endocytic complexes in a temporal and spatial manner. In this work, we examine the dominant interaction sequence in amphiphysin, a synapse-enriched accessory protein, which generates membrane curvature and recruits the scission protein dynamin to the necks of coated pits, for the platform subdomain of the alpha-appendage. The motif domain of amphiphysin1 contains one copy of each of a DX(F/W) and FXDXF motif. We find that the FXDXF motif is the main determinant for the high affinity interaction with the alpha-adaptin appendage. We describe the optimal sequence of the FXDXF motif using thermodynamic and structural data and show how sequence variation controls the affinities of these motifs for the alpha-appendage.

An endophilin-dynamin complex promotes budding of clathrin-coated vesicles during synaptic vesicle recycling

Clathrin-mediated vesicle recycling in synapses is maintained by a unique set of endocytic proteins and interactions. We show that endophilin localizes in the vesicle pool at rest and in spirals at the necks of clathrin-coated pits (CCPs) during activity in lamprey synapses. Endophilin and dynamin colocalize at the base of the clathrin coat. Protein spirals composed of these proteins on lipid tubes in vitro have a pitch similar to the one observed at necks of CCPs in living synapses, and lipid tubules are thinner than those formed by dynamin alone. Tubulation efficiency and the amount of dynamin recruited to lipid tubes are dramatically increased in the presence of endophilin. Blocking the interactions of the endophilin SH3 domain in situ reduces dynamin accumulation at the neck and prevents the formation of elongated necks observed in the presence of GTPγS. Therefore, endophilin recruits dynamin to a restricted part of the CCP neck, forming a complex, which promotes budding of new synaptic vesicles.

2P/Encke, the Taurid complex NEOs and the Maribo and Sutter's Mill meteorites

Aims. 2P/Encke is a short period comet that was discovered in 1786 and has been extensively observed and studied for more than 200years. The Taurid meteoroid stream has long been linked with 2P/Encke owing to a good match of their orbital elements, even thoughthe comet’s activity is not strong enough to explain the number of observed meteors. Various small near-Earth objects (NEOs) havebeen discovered with orbits that can be linked to 2P/Encke and the Taurid meteoroid stream. Maribo and Sutter’s Mill are CM typecarbonaceous chondrite that fell in Denmark on January 17, 2009 and April 22, 2012, respectively. Their pre-atmospheric orbits placethem in the middle of the Taurid meteoroid stream, which raises the intriguing possibility that comet 2P/Encke could be the parentbody of CM chondrites.
Methods. To investigate whether a relationship between comet 2P/Encke, the Taurid complex associated NEOs, and CM chondritesexists, we performed photometric and spectroscopic studies of these objects in the visible wavelength range. We observed 2P/Enckeand 10 NEOs on August 2, 2011 with the FORS instrument at the 8.2 m Very Large Telescope on Cerro Paranal (Chile).
Results. Images in the R filter, used to investigate the possible presence of cometary activity around the nucleus of 2P/Encke andthe NEOs, show that no resolved coma is present. None of the FORS spectra show the 700 nm absorption feature due to hydratedminerals that is seen in the CM chondrite meteorites. All objects show featureless spectra with moderate reddening slopes at λ < 800nm. Apart for 2003 QC10 and 1999 VT25, which show a flatter spectrum, the spectral slope of the observed NEOs is compatible withthat of 2P/Encke. However, most of the NEOs show evidence of a silicate absorption in lower S/N data at λ > 800 nm, which is notseen in 2P/Encke, which suggests that they are not related.
Conclusions. Despite similar orbits, we find no spectroscopic evidence for a link between 2P/Encke, the Taurid complex NEOs andthe Maribo and Sutter’s Mill meteorites. However, we cannot rule out a connection to the meteorites either, as the spectral differencesmay be caused by secondary alteration of the surfaces of the NEOs. 

Design of a Virtual Reality Framework for Maintainability and assemblability test of complex systems

This paper presents a unique environment whose features are able to satisfy requirements for both virtual maintenance and virtual manufacturing through the conception of original virtual reality (VR) architecture. Virtual Reality for the Maintainability and Assemblability Tests (VR_MATE) encompasses VR hardware and software and a simulation manager which allows customisation of the architecture itself as well as interfacing with a wide range of devices employed in the simulations. Two case studies are presented to illustrate VR_MATE's unique ability to allow for both maintainability tests and assembly analysis of an aircraft carriage and a railway coach cooling system respectively. The key impact of this research is the demonstration of the potentialities of using VR techniques in industry and its multiple applications despite the subjective character within the simulation. VR_MATE has been presented as a framework to support the strategic and operative objectives of companies to reduce product development time and costs whilst maintaining product quality for applications which would be too expensive to simulate and evaluate in the real world.

Localized structures in complex plasmas in the presence of a magnetic field

In this work, the general framework in which fits our investigation is that of modeling the dynamics of dust grains therein dusty plasma (complex plasma) in the presence of electromagnetic fields. The generalized discrete complex Ginzburg-Landau equation (DCGLE) is thus obtained to model discrete dynamical structure in dusty plasma with Epstein friction. In the collisionless limit, the equation reduces to the modified discrete nonlinear Schrödinger equation (MDNLSE). The modulational instability phenomenon is studied and we present the criterion of instability in both cases and it is shown that high values of damping extend the instability region. Equations thus obtained highlight the presence of soliton-like excitation in dusty plasma. We studied the generation of soliton in a dusty plasma taking in account the effects of interaction between dust grains and theirs neighbours. Numerical simulations are carried out to show the validity of analytical approach.