40 research outputs found
Advances on the Transfer of Lipids by Lipid Transfer Proteins
Transfer of lipid across the cytoplasm is an essential process for intracellular lipid traffic. Lipid transfer proteins (LTPs) are defined by highly controlled in vitro experiments. The functional relevance of these is supported by evidence for the same reactions inside cells. Major advances in the LTP field have come from structural bioinformatics identifying new LTPs, and from the development of countercurrent models for LTPs. However, the ultimate aim is to unite in vitro and in vivo data, and this is where much progress remains to be made. Even where in vitro and in vivo experiments align, rates of transfer tend not to match. Here we set out some of the advances that might test how LTPs work
Peculiar behaviour of optical polarization gratings in light-sensitive liquid crystalline elastomers
The angular dependence of the diffraction efficiency of volumetype
holographic gratings recorded in a single-domain light-sensitive liquid
crystalline elastomer was investigated. Usually this dependence is expected
to be very similar for intensity gratings and for polarization gratings.
However, our measurements resolved a profound difference between the
two types of the gratings: a typical Bragg peak of the diffraction efficiency
is observed only for intensity gratings, while polarization gratings exhibit a
profound dip at the Bragg angle. The appearance of this dip is explained by
strongly anisotropic optical absorption of the actinic light during the
recording process
Traffic of p24 Proteins and COPII Coat Composition Mutually Influence Membrane Scaffolding
SummaryEukaryotic protein secretion requires efficient and accurate delivery of diverse secretory and membrane proteins. This process initiates in the ER, where vesicles are sculpted by the essential COPII coat. The Sec13p subunit of the COPII coat contributes to membrane scaffolding, which enforces curvature on the nascent vesicle. A requirement for Sec13p can be bypassed when traffic of lumenally oriented membrane proteins is abrogated. Here we sought to further explore the impact of cargo proteins on vesicle formation. We show that efficient ER export of the p24 family of proteins is a major driver of the requirement for Sec13p. The scaffolding burden presented by the p24 complex is met in part by the cargo adaptor Lst1p, which binds to a subset of cargo, including the p24 proteins. We propose that the scaffolding function of Lst1p is required to generate vesicles that can accommodate difficult cargo proteins that include large oligomeric assemblies and asymmetrically distributed membrane proteins. Vesicles that contain such cargoes are also more dependent on scaffolding by Sec13p, and may serve as a model for large carrier formation in other systems
Slow stress relaxation in randomly disordered nematic elastomers and gels
Randomly disordered (polydomain) liquid crystalline elastomers align under
stress. We study the dynamics of stress relaxation before, during and after the
Polydomain-Monodomain transition. The results for different materials show the
universal ultra-slow logarithmic behaviour, especially pronounced in the region
of the transition. The data is approximated very well by an equation Sigma(t) ~
Sigma_{eq} + A/(1+ Alpha Log[t]). We propose a theoretical model based on the
concept of cooperative mechanical resistance for the re-orientation of each
domain, attempting to follow the soft-deformation pathway. The exact model
solution can be approximated by compact analytical expressions valid at short
and at long times of relaxation, with two model parameters determined from the
data.Comment: 4 pages (two-column), 5 EPS figures (included via epsfig
Spontaneous Liquid Crystal and Ferromagnetic Ordering of Colloidal Magnetic Nanoplates
Ferrofluids are familiar as colloidal suspensions of ferromagnetic
nanoparticles in aqueous or organic solvents. The dispersed particles are
randomly oriented but their moments become aligned if a magnetic field is
applied, producing a variety of exotic and useful magneto-mechanical effects. A
longstanding interest and challenge has been to make such suspensions
macroscopically ferromagnetic, that is having uniform magnetic alignment in
absence of a field. Here we report a fluid suspension of magnetic nanoplates
which spontaneously aligns into an equilibrium nematic liquid crystal phase
that is also macroscopically ferromagnetic. Its zero-field magnetization
produces distinctive magnetic self-interaction effects, including liquid
crystal textures of fluid block domains arranged in closed flux loops, and
makes this phase highly sensitive, with it dramatically changing shape even in
the Earth's magnetic field
New molecular mechanisms of inter-organelle lipid transport
International audienc
Solids on Soli: Millimetre-Wave Radar Sensing through Materials
International audienceGesture recognition with miniaturised radar sensors has received increasing attention as a novel interaction medium. The practical use of radar technology, however, often requires sensing through materials. Yet, it is still not well understood how the internal structure of materials impacts recognition performance. To tackle this challenge, we collected a large dataset of 14,090 radar recordings for 6 paradigmatic gesture classes sensed through a variety of everyday materials, performed by humans (6 materials) and a robot system (75 materials). Next, we developed a hybrid CNN+LSTM deep learning model and derived a robust indirect method to measure signal distortions, which we used to compile a comprehensive catalogue of materials for radar-based interaction. Among other findings, our experiments show that it is possible to estimate how different materials would affect gesture recognition performance of arbitrary classifiers by selecting just 3 reference materials. Our catalogue, software, models, data collection platform, and labeled datasets are publicly available