Cooperative long range protein-protein dynamics in Purple Membrane

Membrane tubulation by elongated and patchy nanoparticles

Advances in nanotechnology lead to an increasing interest in how nanoparticles interact with biomembranes. Nanoparticles are wrapped spontaneously by biomembranes if the adhesive interactions between the particles and membranes compensate for the cost of membrane bending. In the last years, the cooperative wrapping of spherical nanoparticles in membrane tubules has been observed in experiments and simulations. For spherical nanoparticles, the stability of the particle-filled membrane tubules strongly depends on the range of the adhesive particle-membrane interactions. In this article, we show …

Directional interactions and cooperativity between mechanosensitive membrane proteins

While modern structural biology has provided us with a rich and diverse picture of membrane proteins, the biological function of membrane proteins is often influenced by the mechanical properties of the surrounding lipid bilayer. Here we explore the relation between the shape of membrane proteins and the cooperative function of membrane proteins induced by membrane-mediated elastic interactions. For the experimental model system of mechanosensitive ion channels we find that the sign and strength of elastic interactions depend on the protein shape, yielding distinct cooperative gating curves fo…

Motional Coherence in Fluid Phospholipid Membranes

We report a high energy-resolution neutron backscattering study, combined with in-situ diffraction, to investigate slow molecular motions on nanosecond time scales in the fluid phase of phospholipid bilayers of 1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine (DMPC) and DMPC/40% cholesterol (wt/wt). A cooperative structural relaxation process was observed. From the in-plane scattering vector dependence of the relaxation rates in hydrogenated and deuterated samples, combined with results from a 0.1 microsecond long all atom molecular dynamics simulation, it is concluded that correlated dynamics …

Cooperative transitions involving hydrophobic polyelectrolytes

Hydrophobic polyelectrolytes (HPE) can solubilize bilayer membranes, form micelles or can reversibly aggregate as a function of pH. The transitions are often remarkably sharp. We show that these cooperative transitions occur by a competition between two or more conformational states and can be explained within the framework of Monod - Wymann - Changeux (MWC) theory that was originally formulated for allosteric interactions. Here we focus on the pH-dependent destabilization and permeation of bilayer membranes by HPE. We formulate the general conditions that lead to sharp conformational transiti…

DMPG膜结构转变与熔化过程的关系及其与水的相互作用

The relationship between the structural transitions of DMPG membranes and the melting process, and their interaction with water

本研究提出一种理论，通过两种可熔化膜几何形状的共存与协同平衡，解释DMPG膜熔化转变中的多峰热容曲线，并揭示水作为膜组成部分的作用。

Periodic spiking by a pair of ionic channels

Neuronal cells present periodic trains of localized voltage spikes involving a large amount of different ionic channels. A relevant question is whether this is a cooperative effect or it could also be an intrinsic property of individual channels. Here we use a Langevin formulation for the stochastic dynamics of a pair of Na and K ionic channels. These two channels are simple gated pore models where a minimum set of degrees of freedom follow standard statistical physics. The whole system is totally autonomous without any external energy input, except for the chemical energy of the different ion…

形状在粒子-脂质膜相互作用中的作用：从滑行到完全吞噬

Role of shape in particle-lipid membrane interactions: from surfing to full engulfment

本研究利用巨型单层囊泡和棒状粒子实验系统，揭示了粒子形状、曲率、取向、膜张力与粘附强度如何共同决定吞噬路径从滑行到完全包裹的转变，并发现棒状团簇的协同包裹行为。

Compatibility between itinerant synaptic receptors and stable postsynaptic structure

The density of synaptic receptors in front of presynaptic release sites is stabilized in the presence of scaffold proteins, but the receptors and scaffold molecules have local exchanges with characteristic times shorter than that of the receptor-scaffold assembly. We propose a mesoscopic model to account for the regulation of the local density of receptors as quasiequilibrium. It is based on two zones (synaptic and extrasynaptic) and multi-layer (membrane, sub-membrane and cytoplasmic) topological organization. The model includes the balance of chemical potentials associated with the receptor …

Mobility of Min-proteins in Escherichia coli measured by fluorescence correlation spectroscopy

In the bacterium Escherichia coli, selection of the division site involves pole-to-pole oscillations of the proteins MinD and MinE. Different oscillation mechanisms based on cooperative effects between Min-proteins and on the exchange of Min-proteins between the cytoplasm and the cytoplasmic membrane have been proposed. The parameters characterizing the dynamics of the Min-proteins in vivo are not known. It has therefore been difficult to compare the models quantitatively with experiments. Here, we present in vivo measurements of the mobility of MinD and MinE using fluorescence correlation spe…

Collective response of self-organised clusters of mechanosensitive channels

Mechanosensitive channels are ion channels activated by membrane tension. We investigate the influence of bacterial mechanosensitive channels spatial distribution on activation (gating). Based on elastic short-range interactions we map this physical process onto an Ising-like model, which enables us to predict the clustering of channels and the effects of clustering on their gating. We conclude that the aggregation of channels and the consequent interactions among them leads to a global cooperative gating behaviour with potentially dramatic consequences for the cell.