The self-assembly, aggregation and phase transitions of food protein systems in one, two and three dimensions

2013 ◽  
Vol 76 (4) ◽  
pp. 046601 ◽  
Author(s):  
Raffaele Mezzenga ◽  
Peter Fischer
Keyword(s):  
Phase Transitions ◽  
Self Assembly ◽  
The Self ◽  
Three Dimensions ◽  
Food Protein

A Model of Force Generation in a Three-Dimensional Toroidal Cluster of Cells

2012 ◽  
Vol 79 (5) ◽  
Author(s):  
Asha Nurse ◽  
L. B. Freund ◽  
Jacquelyn Youssef
Keyword(s):  
Potential Energy ◽  
Gravitational Potential ◽  
Self Assembly ◽  
Three Dimensional ◽  
Dissipative System ◽  
The Self ◽  
Three Dimensions ◽  
Force Generation ◽  
Gravitational Potential Energy ◽  
Kinetics Of

Observation of the self-assembly of clusters of cells in three dimensions has raised questions about the forces that drive changes in the shape of the cell clusters. Cells that self-assemble into a toroidal cluster about the base of a conical pillar have been observed in the laboratory to spontaneously climb the conical pillar. Assuming that cell cluster reorganization is due solely to surface diffusion, a mathematical model based on the thermodynamics of an isothermal dissipative system is presented. The model shows that the cluster can reduce its surface area by climbing the conical pillar, however, this is at the expense of increasing its gravitational potential energy. As a result, the kinetics of the climb are affected by parameters that influence this energy competition, such as the slope of the conical pillar and a parameter of the model κ that represents the influence of the surface energy of the cluster relative to its gravitational potential energy.

scholarly journals Ubiquitous deprotonation of terephthalic acid in the self-assembled phases on Cu(100)

2018 ◽  
Vol 20 (6) ◽  
pp. 4329-4339 ◽  
Author(s):  
B. Quiroga Argañaraz ◽  
L. J. Cristina ◽  
L. M. Rodríguez ◽  
A. Cossaro ◽  
A. Verdini ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Self Assembly ◽  
Terephthalic Acid ◽  
The Self ◽  
Temperature Range ◽  
Self Assembled ◽  
Exhaustive Study ◽  
Sequential Phase

We performed an exhaustive study of terephthalic acid (TPA) self-assembly on a Cu(100) surface, where first-layer molecules display three sequential phase transitions in the 200–400 K temperature range, corresponding to different stages of molecular deprotonation.

Evolution of Carbon Self-Assembly in Colloidal Phase Diagram

2002 ◽  
Vol 739 ◽  
Author(s):  
V. Bouda
Keyword(s):  
Phase Diagram ◽  
Phase Transitions ◽  
Self Assembly ◽  
Colloidal Particles ◽  
Thermal Fluctuation ◽  
Ionic Concentration ◽  
The Self ◽  
Colloidal Systems ◽  
Carbon Particles ◽  
Self Assembled

ABSTRACTThe growth of the self-assembled structure of carbon colloidal particles has been studied [1]. The system of carbon particles was processed in electrical field in polymer melt with controlled ionic concentration. The interpretation of the complex evolution of the self-assembled structure of carbon particles was given in terms of phase transitions of colloidal systems of carbon particles.Interactions between doublets of carbon black (CB) particles are interpreted in terms of DLVO approximation of interaction energy as multiples of average thermal fluctuation kT. Plots of the sum of energy of electrostatic repulsion and energy of van der Waals attraction versus separation between the doublets show the energy barriers to coagulation of high B and the energy wells with the secondary minima of depth W. The colloidal phase transitions appear at critical conjuncture of the concentration of ions in the medium and surface potential on the colloids. Six transition lines determine five phases of the assembly of carbon colloids in the proposed colloidal phase diagram: lateral vapor + axial vapor (vapor), lateral liquid + axial vapor (columnar liquid crystal), lateral liquid + axial liquid (smectic LC), lateral liquid + axial solid (nematic LC), and lateral solid + axial solid (solid).The diagram provides a tool to control the evolution of carbon self-assembly. The eventual morphology depends on the route of the steps of the processing. During the time elapsed in the LC state, the structure can reorganize and the eventual coagulation produces various crystals. On the contrary, the route outside the LC state can produce glass.

Making Things by Self-Assembly

MRS Bulletin ◽  
2005 ◽  
Vol 30 (10) ◽  
pp. 736-742 ◽  
Author(s):  
Mila Boncheva ◽  
George M. Whitesides
Keyword(s):  
Self Assembly ◽  
Process Variations ◽  
The Self ◽  
Three Dimensions ◽  
Spontaneous Generation ◽  
Curved Surfaces ◽  
Proof Of Concept ◽  
Small Complex ◽  
New Methodologies ◽  
Functional Components

AbstractSelf-assembly—the spontaneous generation of order in systems of components—is ubiquitous in chemistry; in biology, it generates much of the functionality of the living cell. Self-assembly is relatively unused in microfabrication, although it offers opportunities to simplify processes, lower costs, develop new processes, use components too small to be manipulated robotically, integrate components made using incompatible technologies, and generate structures in three dimensions and on curved surfaces. The major limitations to the self-assembly of micrometer- to millimeter-sized components (mesoscale self-assembly) do not seem to be intrinsic, but rather operational: selfassembly can, in fact, be reliable and insensitive to small process variations, but fabricating the small, complex, functional components that future applications may require will necessitate the development of new methodologies. Proof-of-concept experiments in mesoscale self-assembly demonstrate that this technique poses fascinating scientific and technical challenges and offers the potential to provide access to hard-to-fabricate structures.

Three-dimensional cell culture of chondrocytes on modified di-phenylalanine scaffolds

2007 ◽  
Vol 35 (3) ◽  
pp. 535-537 ◽  
Author(s):  
V. Jayawarna ◽  
A. Smith ◽  
J.E. Gough ◽  
R.V. Ulijn
Keyword(s):  
Electron Microscopy ◽  
Cell Culture ◽  
Cell Proliferation ◽  
Self Assembly ◽  
Three Dimensional ◽  
Building Blocks ◽  
Culture Conditions ◽  
The Self ◽  
Three Dimensions ◽  
Dimensional Cell

The design of self-assembled peptide-based structures for three-dimensional cell culture and tissue repair has been a key objective in biomaterials science for decades. In search of the simplest possible peptide system that can self-assemble, we discovered that combinations of di-peptides that are modified with aromatic stacking ligands could form nanometre-sized fibres when exposed to physiological conditions. For example, we demonstrated that a number of Fmoc (fluoren-9-ylmethyloxycarbonyl) modified di- and tri-peptides form highly ordered hydrogels via hydrogen-bonding and π–π interactions from the fluorenyl rings. These highly hydrated gels allowed for cell proliferation of chondrocytes in three dimensions [Jayawarna, Ali, Jowitt, Miller, Saiani, Gough and Ulijn (2006) Adv. Mater. 18, 611–614]. We demonstrated that fibrous architecture and physical properties of the resulting materials were dictated by the nature of the amino acid building blocks. Here, we report the self-assembly process of three di-phenylalanine analogues, Fmoc-Phe-Phe-OH, Nap (naphthalene)-Phe-Phe-OH and Cbz (benzyloxycarbonyl)-Phe-Phe-OH, to compare and contrast the self-assembly properties and cell culture conditions attributable to their protecting group difference. Fibre morphology analysis of the three structures using cryo-SEM (scanning electron microscopy) and TEM (transmission electron microscopy) suggested fibrous structures with dramatically varying fibril dimensions, depending on the aromatic ligand used. CD and FTIR (Fourier-transform IR) data confirmed β-sheet arrangements in all three samples in the gel state. The ability of these three new hydrogels to support cell proliferation of chondrocytes was confirmed for all three materials.

The Nature of Rapidly Extracted Phycocyanin from the Blue-Green Alga Plectonema Boryanum

1971 ◽  
Vol 29 ◽  
pp. 366-367
Author(s):  
M. Kessel ◽  
R. MacColl
Keyword(s):  
Self Assembly ◽  
Analytical Ultracentrifugation ◽  
Uranyl Acetate ◽  
The Self ◽  
Major Protein ◽  
Subunit Structure ◽  
Blue Green Alga ◽  
Thin Sections ◽  
Blue Green Algae ◽  
Cacodylate Buffer

The major protein of the blue-green algae is the biliprotein, C-phycocyanin (Amax = 620 nm), which is presumed to exist in the cell in the form of distinct aggregates called phycobilisomes. The self-assembly of C-phycocyanin from monomer to hexamer has been extensively studied, but the proposed next step in the assembly of a phycobilisome, the formation of 19s subunits, is completely unknown. We have used electron microscopy and analytical ultracentrifugation in combination with a method for rapid and gentle extraction of phycocyanin to study its subunit structure and assembly.To establish the existence of phycobilisomes, cells of P. boryanum in the log phase of growth, growing at a light intensity of 200 foot candles, were fixed in 2% glutaraldehyde in 0.1M cacodylate buffer, pH 7.0, for 3 hours at 4°C. The cells were post-fixed in 1% OsO4 in the same buffer overnight. Material was stained for 1 hour in uranyl acetate (1%), dehydrated and embedded in araldite and examined in thin sections.

Interrelationship of the cellular distribution and secretion of regular structure (RS) protein in Bacillus licheniformis nm 105

1992 ◽  
Vol 50 (1) ◽  
pp. 712-713
Author(s):  
Xiaorong Zhu ◽  
Richard McVeigh ◽  
Bijan K. Ghosh
Keyword(s):  
Alkaline Phosphatase ◽  
Bacillus Licheniformis ◽  
Self Assembly ◽  
Gel Electrophoresis ◽  
Culture Supernatant ◽  
Regular Structure ◽  
The Self ◽  
Cellular Distribution ◽  
Structural Protein ◽  
Laboratory Cultures

A mutant of Bacillus licheniformis 749/C, NM 105 exhibits some notable properties, e.g., arrest of alkaline phosphatase secretion and overexpression and hypersecretion of RS protein. Although RS is known to be widely distributed in many microbes, it is rarely found, with a few exceptions, in laboratory cultures of microorganisms. RS protein is a structural protein and has the unusual properties to form aggregate. This characteristic may have been responsible for the self assembly of RS into regular tetragonal structures. Another uncommon characteristic of RS is that enhanced synthesis and secretion which occurs when the cells cease to grow. Assembled RS protein with a tetragonal structure is not seen inside cells at any stage of cell growth including cells in the stationary phase of growth. Gel electrophoresis of the culture supernatant shows a very large amount of RS protein in the stationary culture of the B. licheniformis. It seems, Therefore, that the RS protein is cotranslationally secreted and self assembled on the envelope surface.

Nanoscale Self-Assembly Using Ion and Electron Beam Techniques: A Rapid Review

MRS Advances ◽  
2020 ◽  
Vol 5 (64) ◽  
pp. 3507-3520
Author(s):  
Chunhui Dai ◽  
Kriti Agarwal ◽  
Jeong-Hyun Cho
Keyword(s):  
Electron Beam ◽  
Self Assembly ◽  
Ion Beam ◽  
Three Dimensional ◽  
The Self ◽  
Stress Generation ◽  
Rapid Review ◽  
High Yield ◽  
3D Nanostructures ◽  
Self Assembled

AbstractNanoscale self-assembly, as a technique to transform two-dimensional (2D) planar patterns into three-dimensional (3D) nanoscale architectures, has achieved tremendous success in the past decade. However, an assembly process at nanoscale is easily affected by small unavoidable variations in sample conditions and reaction environment, resulting in a low yield. Recently, in-situ monitored self-assembly based on ion and electron irradiation has stood out as a promising candidate to overcome this limitation. The usage of ion and electron beam allows stress generation and real-time observation simultaneously, which significantly enhances the controllability of self-assembly. This enables the realization of various complex 3D nanostructures with a high yield. The additional dimension of the self-assembled 3D nanostructures opens the possibility to explore novel properties that cannot be demonstrated in 2D planar patterns. Here, we present a rapid review on the recent achievements and challenges in nanoscale self-assembly using electron and ion beam techniques, followed by a discussion of the novel optical properties achieved in the self-assembled 3D nanostructures.

Bottom-up Evolution from Disks to High-Genus Polymersomes

2018 ◽  
Author(s):  
Claudia Contini ◽  
Russell Pearson ◽  
Linge Wang ◽  
Lea Messager ◽  
Jens Gaitzsch ◽  
...  
Keyword(s):  
Self Assembly ◽  
The Self ◽  
Amphiphilic Copolymers ◽  
Chain Entanglement ◽  
Bottom Up ◽  
New Approach ◽  
High Genus ◽  
Transmission Electron ◽  
Minimal Radius ◽  
Stop Flow

<div><div><div><p>We report the design of polymersomes using a bottom-up approach where the self-assembly of amphiphilic copolymers poly(2-(methacryloyloxy) ethyl phosphorylcholine)–poly(2-(diisopropylamino) ethyl methacrylate) (PMPC-PDPA) into membranes is tuned using pH and temperature. We study this process in detail using transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) spectroscopy, dynamic light scattering (DLS), and stop-flow ab- sorbance disclosing the molecular and supramolecular anatomy of each structure observed. We report a clear evolution from disk micelles to vesicle to high-genus vesicles where each passage is controlled by pH switch or temperature. We show that the process can be rationalised adapting membrane physics theories disclosing important scaling principles that allow the estimation of the vesiculation minimal radius as well as chain entanglement and coupling. This allows us to propose a new approach to generate nanoscale vesicles with genus from 0 to 70 which have been very elusive and difficult to control so far.</p></div></div></div>

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