scholarly journals Purely entropic self-assembly of the bicontinuous Ia 3 d gyroid phase in equilibrium hard-pear systems

2017 ◽  
Vol 7 (4) ◽  
pp. 20160161 ◽  
Author(s):  
Philipp W. A. Schönhöfer ◽  
Laurence J. Ellison ◽  
Matthieu Marechal ◽  
Douglas J. Cleaver ◽  
Gerd E. Schröder-Turk
Keyword(s):  
Phase Diagram ◽  
Minimal Surface ◽  
Lipid Bilayers ◽  
Self Assembly ◽  
Particle Shape ◽  
Voronoi Tessellation ◽  
Gauss Curvature ◽  
Constant Density ◽  
Continuous Change ◽  
Link Type

We investigate a model of hard pear-shaped particles which forms the bicontinuous Ia d structure by entropic self-assembly, extending the previous observations of Barmes et al. (2003 Phys. Rev. E 68 , 021708. ( doi:10.1103/PhysRevE.68.021708 )) and Ellison et al. (2006 Phys. Rev. Lett. 97 , 237801. ( doi:10.1103/PhysRevLett.97.237801 )). We specifically provide the complete phase diagram of this system, with global density and particle shape as the two variable parameters, incorporating the gyroid phase as well as disordered isotropic, smectic and nematic phases. The phase diagram is obtained by two methods, one being a compression–decompression study and the other being a continuous change of the particle shape parameter at constant density. Additionally, we probe the mechanism by which interdigitating sheets of pears in these systems create surfaces with negative Gauss curvature, which is needed to form the gyroid minimal surface. This is achieved by the use of Voronoi tessellation, whereby both the shape and volume of Voronoi cells can be assessed in regard to the local Gauss curvature of the gyroid minimal surface. Through this, we show that the mechanisms prevalent in this entropy-driven system differ from those found in systems which form gyroid structures in nature (lipid bilayers) and from synthesized materials (di-block copolymers) and where the formation of the gyroid is enthalpically driven. We further argue that the gyroid phase formed in these systems is a realization of a modulated splay-bend phase in which the conventional nematic has been predicted to be destabilized at the mesoscale due to molecular-scale coupling of polar and orientational degrees of freedom.

A Self-Assembly Phase Diagram from Amphiphilic Perylene Diimides

2012 ◽  
Vol 18 (39) ◽  
pp. 12305-12313 ◽  
Author(s):  
Zhigang Zhang ◽  
Chuanlang Zhan ◽  
Xin Zhang ◽  
Shanlin Zhang ◽  
Jianhua Huang ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Self Assembly ◽  
Perylene Diimides

scholarly journals Local minima of the Gauss curvature of a minimal surface

1991 ◽  
Vol 44 (3) ◽  
pp. 397-404
Author(s):  
Shinji Yamashita
Keyword(s):  
Minimal Surface ◽  
Gauss Curvature ◽  
Gauss Map ◽  
Local Minima ◽  
Jordan Curves ◽  
The Third ◽  
Isolated Points ◽  
Set Of Points

Let D be a domain in the complex ω-plane and let x: D → R3 be a regular minimal surface. Let M(K) be the set of points ω0 ∈ D where the Gauss curvature K attains local minima: K(ω0) ≤ K(ω) for |ω – ω0| < δ(ω0), δ(ω0) < 0. The components of M(K) are of three types: isolated points; simple analytic arcs terminating nowhere in D; analytic Jordan curves in D. Components of the third type are related to the Gauss map.

scholarly journals S-Layer Self-Assembly on Supported Lipid-Bilayers: The Importance of Amorphous Precursors and Folding Transitions

2010 ◽  
Vol 98 (3) ◽  
pp. 10a
Author(s):  
Sungwook Chung ◽  
Seong-Ho Shin ◽  
Stephen Whitelam ◽  
Carolyn Bertozzi ◽  
Jim De Yoreo
Keyword(s):  
Lipid Bilayers ◽  
Self Assembly ◽  
Supported Lipid Bilayers

scholarly journals On the Kinetics of Adsorption and Two-Dimensional Self-Assembly of Annexin A5 on Supported Lipid Bilayers

2005 ◽  
Vol 89 (5) ◽  
pp. 3372-3385 ◽  
Author(s):  
Ralf P. Richter ◽  
Joséphine Lai Kee Him ◽  
Béatrice Tessier ◽  
Céline Tessier ◽  
Alain R. Brisson
Keyword(s):  
Lipid Bilayers ◽  
Self Assembly ◽  
Supported Lipid Bilayers ◽  
Annexin A5 ◽  
Two Dimensional ◽  
Kinetics Of Adsorption ◽  
Kinetics Of

scholarly journals The self assembly of proteins; probing patchy protein interactions

2015 ◽  
Vol 17 (7) ◽  
pp. 5413-5420 ◽  
Author(s):  
Susan James ◽  
Michelle K. Quinn ◽  
Jennifer J. McManus
Keyword(s):  
Phase Diagram ◽  
Thermodynamic Properties ◽  
Protein Interactions ◽  
Self Assembly ◽  
The Self ◽  
Protein Surface ◽  
Competing Interactions ◽  
Diagram Approach

Anisotropy is central to protein self-assembly. The kinetic and thermodynamic properties of proteins in which competing interactions exist due to the anisotropic or patchy nature of the protein surface have been explored using a phase diagram approach.

scholarly journals Towards Complex Matter: Supramolecular Chemistry and Self-organization

2009 ◽  
Vol 17 (2) ◽  
pp. 263-280 ◽  
Author(s):  
Jean-Marie Lehn
Keyword(s):  
Supramolecular Chemistry ◽  
Self Assembly ◽  
Building Blocks ◽  
Intermolecular Forces ◽  
Self Organization ◽  
Irreversible Processes ◽  
Continuous Change ◽  
Supramolecular Systems ◽  
Molecular Information ◽  
Complex Matter

Chemistry has developed from molecular chemistry, mastering the combination and recombination of atoms into increasingly complex molecules, to supramolecular chemistry, harnessing intermolecular forces for the generation of informed supramolecular systems and processes through the implementation of molecular information carried by electromagnetic interactions. Supramolecular chemistry is actively exploring systems undergoing self-organization, i.e. systems capable of spontaneously generating well-defined functional supramolecular architectures by self-assembly from their components, on the basis of the molecular information stored in the covalent framework of the components and read out at the supramolecular level through specific molecular recognition interactional algorithms, thus behaving as programmed chemical systems. Supramolecular entities as well as molecules containing reversible bonds are able to undergo a continuous change in constitution by reorganization and exchange of building blocks. This capability defines a Constitutional Dynamic Chemistry (CDC) on both the molecular and supramolecular levels. CDC introduces a paradigm shift with respect to constitutionally static chemistry. It takes advantage of dynamic constitutional diversity to allow variation and selection and thus adaptation. The merging of the features of supramolecular systems – information and programmability; dynamics and reversibility; constitution and structural diversity – points towards the emergence of adaptive chemistry. A further development will concern the inclusion of the arrow of time, i.e. of non-equilibrium, irreversible processes and the exploration of the frontiers of chemical evolution towards the establishment of evolutive chemistry, where the features acquired by adaptation are conserved and transmitted. In combination with the corresponding fields of physics and biology, chemistry thus plays a major role in the progressive elaboration of a science of informed, organized, evolutive matter, a science of complex matter.

scholarly journals Repositioning septins within the core particle

2019 ◽  
Author(s):  
Deborah C. Mendonça ◽  
Joci N. Macedo ◽  
Rosangela Itri ◽  
Samuel L. Guimaraes ◽  
Fernando L. Barroso da Silva ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Self Assembly ◽  
Binding Proteins ◽  
Structural Information ◽  
Core Particle ◽  
Affinity Tag ◽  
The Core ◽  
Gtp Binding ◽  
True Structure ◽  
Core Particles

AbstractSeptins are GTP binding proteins considered to be a novel component of the cytoskeleton. They polymerize into filaments based on hetero-oligomeric core particles which, in humans, are either hexamers or octamers composed of two copies each of either three or four different septins from the 13 available. Not all combinations are possible as it is believed that these must obey substitution rules which determine that different septins must be derived from four distinct and well-established sub-groups. Here, we have purified and characterized one such combinations, SEPT5-SEPT6-SEPT7, and used TEM to derive the first structural information concerning its assembly. The full complex was purified using an affinity tag attached to only one of its components (SEPT7) and was able to bind to and perturb lipid bilayers. Although the complex assembled into elongated hexameric particles, the position of SEPT5 was incompatible with that predicted by the reported structure of SEPT2-SEPT6-SEPT7 based on the substitution rules. MBP-fusion constructs for SEPT5 and SEPT2 and immuno-staining clearly show that these septins occupy the terminal positions of the SEPT5-SEPT6-SEPT7 and SEPT2-SEPT6-SEPT7 hexamers, respectively. In so doing they expose a so-called NC interface which we show to be more susceptible to perturbation at high salt concentrations. Our results show that the true structure of the hexamer is inverted with respect to that described previously and, as such, is more compatible with that reported for yeast. Taken together, our results suggest that the mechanisms involved in spontaneous self-assembly of septin core particles and their filaments deserve further reflection.

scholarly journals Vesicle capture by discrete self-assembled clusters of membrane-bound Munc13

2020 ◽  
Author(s):  
Feng Li ◽  
Venkat Kalyana Sundaram ◽  
Alberto T. Gatta ◽  
Jeff Coleman ◽  
Shyam S. Krishnakumar ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Self Assembly ◽  
Synaptic Vesicles ◽  
Supported Lipid Bilayers ◽  
Membrane Domains ◽  
Vesicle Docking ◽  
Multiple Copies ◽  
Membrane Bound ◽  
Small Unilamellar Vesicles ◽  
Active Zones

ABSTRACTMunc13 is a large banana-shaped soluble protein that is involved in the regulation of synaptic vesicle docking and fusion. Recent studies suggested that multiple copies of Munc13 form nanoassemblies in active zones of neurons. However, it is not known if such clustering is an inherent self-assembly property of Munc13 or whether Munc13 clusters indirectly by multivalent binding to synaptic vesicles or specific plasma membrane domains at docking sites in the active zone. The functional significance of putative Munc13 clustering is also unknown. Here we report that nano-clustering is an inherent property of Munc13, and is indeed required for vesicle binding to bilayers containing Munc13. Pure Munc13 reconstituted onto supported lipid bilayers assembled into clusters containing from 2 to ∼20 copies as revealed by a combination of quantitative TIRF microscopy and step-wise photobleaching. Surprisingly, only clusters a minimum of 6 copies of Munc13 were capable of efficiently capturing and retaining small unilamellar vesicles. The C-terminal C2C domain of Munc13 is not required for Munc13 clustering, but is required for efficient vesicle capture.

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