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Garcia-Saez A.J.,Max Planck Institute for Intelligent Systems (Stuttgart) | Garcia-Saez A.J.,German Cancer Research Center
Cell Death and Differentiation | Year: 2012

The Bcl-2 family of proteins is formed by pro-and antiapoptotic members. Together they regulate the permeabilization of the mitochondrial outer membrane, a key step in apoptosis. Their complex network of interactions both in the cytosol and on mitochondria determines the fate of the cell. In the past 2 decades, the members of the family have been identified and classified according to their function. Several competing models have been proposed to explain how the Blc-2 proteins orchestrate apoptosis signaling. However, basic aspects of the action of these proteins remain elusive. This review is focused on the biophysical mechanisms that are relevant for their action in apoptosis and on the challenging gaps in our knowledge that necessitate further exploration to finally understand how the Bcl-2 family regulates apoptosis. © 2012 Macmillan Publishers Limited. All rights reserved.

Roke S.,Institute of Bioengineering IBI | Roke S.,Max Planck Institute for Intelligent Systems (Stuttgart) | Gonella G.,Temple University
Annual Review of Physical Chemistry | Year: 2012

Nano -and microparticles have optical, structural, and chemical properties that differ from both their building blocks and the bulk materials themselves. These different physical and chemical properties are induced by the high surface-to-volume ratio. As a logical consequence, to understand the properties of nano- and microparticles, it is of fundamental importance to characterize the particle surfaces and their interactions with the surrounding medium. Recent developments of nonlinear light scattering techniques have resulted in a deeper insight of the underlying light-matter interactions. They have shed new light on the molecular mechanism of surface kinetics in solution, properties of interfacial water in contact with hydrophilic and hydrophobic particles and droplets, molecular orientation distribution of molecules at particle surfaces in solution, interfacial structure of surfactants at droplet interfaces, acid-base chemistry on particles in solution, and vesicle structure and transport properties. Copyright © 2012 by Annual Reviews. All rights reserved.

Fahnle M.,Max Planck Institute for Intelligent Systems (Stuttgart)
Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2011

For metallic magnets we review the experimental and electron-theoretical investigations of fast magnetization dynamics (on a timescale of ns to 100 ps) and of laser-pulse-induced ultrafast dynamics (few hundred fs). It is argued that for both situations the dominant contributions to the dissipative part of the dynamics arise from the excitation of electron-hole pairs and from the subsequent relaxation of these pairs by spin-dependent scattering processes, which transfer angular momentum to the lattice. By effective field theories (generalized breathing and bubbling Fermi-surface models) it is shown that the Gilbert equation of motion, which is often used to describe the fast dissipative magnetization dynamics, must be extended in several aspects. The basic assumptions of the Elliott-Yafet theory, which is often used to describe the ultrafast spin relaxation after laser-pulse irradiation, are discussed very critically. However, it is shown that for Ni this theory probably yields a value for the spin-relaxation time T(1) in good agreement with the experimental value. A relation between the quantity α characterizing the damping of the fast dynamics in simple situations and the time T(1) is derived. © 2011 IOP Publishing Ltd

Mark A.G.,Max Planck Institute for Intelligent Systems (Stuttgart) | Gibbs J.G.,Max Planck Institute for Intelligent Systems (Stuttgart) | Lee T.-C.,Max Planck Institute for Intelligent Systems (Stuttgart) | Fischer P.,Max Planck Institute for Intelligent Systems (Stuttgart)
Nature Materials | Year: 2013

Tuning the optical, electromagnetic and mechanical properties of a material requires simultaneous control over its composition and shape. This is particularly challenging for complex structures at the nanoscale because surface-energy minimization generally causes small structures to be highly symmetric. Here we combine low-temperature shadow deposition with nanoscale patterning to realize nanocolloids with anisotropic three-dimensional shapes, feature sizes down to 20 nm and a wide choice of materials. We demonstrate the versatility of the fabrication scheme by growing three-dimensional hybrid nanostructures that contain several functional materials with the lowest possible symmetry, and by fabricating hundreds of billions of plasmonic nanohelices, which we use as chiral metafluids with record circular dichroism and tunable chiroptical properties. © 2013 Macmillan Publishers Limited. All rights reserved.

Hofling F.,Max Planck Institute for Intelligent Systems (Stuttgart) | Hofling F.,University of Stuttgart | Franosch T.,Friedrich - Alexander - University, Erlangen - Nuremberg
Reports on Progress in Physics | Year: 2013

A ubiquitous observation in cell biology is that the diffusive motion of macromolecules and organelles is anomalous, and a description simply based on the conventional diffusion equation with diffusion constants measured in dilute solution fails. This is commonly attributed to macromolecular crowding in the interior of cells and in cellular membranes, summarizing their densely packed and heterogeneous structures. The most familiar phenomenon is a sublinear, power-law increase of the mean-square displacement (MSD) as a function of the lag time, but there are other manifestations like strongly reduced and time-dependent diffusion coefficients, persistent correlations in time, non-Gaussian distributions of spatial displacements, heterogeneous diffusion and a fraction of immobile particles. After a general introduction to the statistical description of slow, anomalous transport, we summarize some widely used theoretical models: Gaussian models like fractional Brownian motion and Langevin equations for visco-elastic media, the continuous-time random walk model, and the Lorentz model describing obstructed transport in a heterogeneous environment. Particular emphasis is put on the spatio-temporal properties of the transport in terms of two-point correlation functions, dynamic scaling behaviour, and how the models are distinguished by their propagators even if the MSDs are identical. Then, we review the theory underlying commonly applied experimental techniques in the presence of anomalous transport like single-particle tracking, fluorescence correlation spectroscopy (FCS) and fluorescence recovery after photobleaching (FRAP). We report on the large body of recent experimental evidence for anomalous transport in crowded biological media: in cyto- and nucleoplasm as well as in cellular membranes, complemented by in vitro experiments where a variety of model systems mimic physiological crowding conditions. Finally, computer simulations are discussed which play an important role in testing the theoretical models and corroborating the experimental findings. The review is completed by a synthesis of the theoretical and experimental progress identifying open questions for future investigation. © 2013 IOP Publishing Ltd.

Soler L.,Max Planck Institute for Intelligent Systems (Stuttgart) | Sanchez S.,Max Planck Institute for Intelligent Systems (Stuttgart)
Nanoscale | Year: 2014

Self-propelled nanomotors hold considerable promise for developing innovative environmental applications. This review highlights the recent progress in the use of self-propelled nanomotors for water remediation and environmental monitoring applications, as well as the effect of the environmental conditions on the dynamics of nanomotors. Artificial nanomotors can sense different analytes - and therefore pollutants, or "chemical threats" - can be used for testing the quality of water, selective removal of oil, and alteration of their speeds, depending on the presence of some substances in the solution in which they swim. Newly introduced micromotors with double functionality to mix liquids at the microscale and enhance chemical reactions for the degradation of organic pollutants greatly broadens the range of applications to that of environmental. These "self-powered remediation systems" could be seen as a new generation of "smart devices" for cleaning water in small pipes or cavities difficult to reach with traditional methods. With constant improvement and considering the key challenges, we expect that artificial nanomachines could play an important role in environmental applications in the near future. © 2014 the Partner Organisations.

Koch C.T.,Max Planck Institute for Intelligent Systems (Stuttgart)
Ultramicroscopy | Year: 2011

The application of convergent beam electron diffraction (CBED) to determine symmetry, refine structure factors, and measure specimen thickness requires rather thick specimen and is very difficult or even impossible in the case of large unit cell materials. The large-angle rocking-beam electron diffraction (LARBED) technique introduced in this paper gives access to the kind of experimental data contained in CBED patterns but over a much larger angular range. In addition to symmetry determination and thickness measurement even for thin samples this technique also allows, in principle, very accurate measurements of structure factors. Similar to precession electron diffraction (PED), LARBED uses the illumination tilt coils to sequentially change the angle of incidence of the electron beam over a very large range. I will present results obtained by a recently developed self-calibrating acquisition software which compensates for aberration-induced probe shifts during the acquisition of LARBED patterns and keeps the probe within a few nm, while covering a tilt range from 0 to 100. mrad. This paper is dedicated to Prof. John C. H. Spence on the occasion of his 65th birthday. © 2010 Elsevier B.V.

Blickle V.,University of Stuttgart | Blickle V.,Max Planck Institute for Intelligent Systems (Stuttgart) | Bechinger C.,University of Stuttgart | Bechinger C.,Max Planck Institute for Intelligent Systems (Stuttgart)
Nature Physics | Year: 2012

The conversion of energy into mechanical work is essential for almost any industrial process. The original description of classical heat engines by Sadi Carnot in 1824 has largely shaped our understanding of work and heat exchange during macroscopic thermodynamic processes. Equipped with our present-day ability to design and control mechanical devices at micro- and nanometre length scales, we are now in a position to explore the limitations of classical thermodynamics, arising on scales for which thermal fluctuations are important. Here we demonstrate the experimental realization of a microscopic heat engine, comprising a single colloidal particle subject to a time-dependent optical laser trap. The work associated with the system is a fluctuating quantity, and depends strongly on the cycle duration time, which in turn determines the efficiency of our heat engine. Our experiments offer a rare insight into the conversion of thermal to mechanical energy on a microscopic level, and pave the way for the design of future micromechanical machines. © 2012 Macmillan Publishers Limited. All rights reserved.

Hirscher M.,Max Planck Institute for Intelligent Systems (Stuttgart)
Angewandte Chemie - International Edition | Year: 2011

Take it to the limit: Ultrahigh-porosity metal-organic frameworks (MOFs) with extremely high specific surface areas show very high hydrogen uptake by physisorption at low temperatures. The total hydrogen storage capacity of MOF-210 through cryoadsorption exceeds even that of complex hydrides. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Palagi S.,Max Planck Institute for Intelligent Systems (Stuttgart)
Nature Materials | Year: 2016

Microorganisms move in challenging environments by periodic changes in body shape. In contrast, current artificial microrobots cannot actively deform, exhibiting at best passive bending under external fields. Here, by taking advantage of the wireless, scalable and spatiotemporally selective capabilities that light allows, we show that soft microrobots consisting of photoactive liquid-crystal elastomers can be driven by structured monochromatic light to perform sophisticated biomimetic motions. We realize continuum yet selectively addressable artificial microswimmers that generate travelling-wave motions to self-propel without external forces or torques, as well as microrobots capable of versatile locomotion behaviours on demand. Both theoretical predictions and experimental results confirm that multiple gaits, mimicking either symplectic or antiplectic metachrony of ciliate protozoa, can be achieved with single microswimmers. The principle of using structured light can be extended to other applications that require microscale actuation with sophisticated spatiotemporal coordination for advanced microrobotic technologies. © 2016 Nature Publishing Group

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