scholarly journals Mimicking pollen and spore walls: self-assembly in action

2019 ◽  
Vol 123 (7) ◽  
pp. 1205-1218 ◽  
Author(s):  
Nina I Gabarayeva ◽  
Valentina V Grigorjeva ◽  
Alexey L Shavarda
Keyword(s):  
Self Assembly ◽  
Original Method ◽  
Pollen Grain ◽  
Periplasmic Space ◽  
Self Assembling ◽  
Transmission Electron ◽  
Physico Chemical ◽  
Spore Walls ◽  
Pattern Determination

Abstract Background and Aims Decades of research have attempted to elucidate the underlying developmental mechanisms that give rise to the enormous diversity of pollen and spore exines. The organization of the exine starts with the establishment of an elaborate glycocalyx within which the subsequent accumulation of sporopollenin occurs. Ontogenetic studies using transmission electron microscopy of over 30 species from many different groups have shown that the sequence of structures observed during development of the exine corresponds to the sequence of self-assembling micellar mesophases (including liquid crystals) observed at increasing concentrations of surfactants. This suggested that self-assembly plays an important part in exine pattern determination. Some patterns resembling separate layers of spore and pollen grain walls have been obtained experimentally, in vitro, by self-assembly. However, to firmly establish this idea, columellate and granulate exines, the most widespread forms, needed to be simulated experimentally. Methods We used our original method, preparing mixtures of substances analogous to those known to occur in the periplasmic space of developing microspores, then leaving the mixtures undisturbed for specific periods of time to allow the process of self-assembly to occur. We developed our method further by using new substances analogous to those present in the periplasmic space and performing the experiments in a thin layer, more closely resembling the dimensions of the periplasmic space. Key Results The artificial microstructures obtained from our in vitro self-assembly experiments closely resembled the main types of exines, including tectate–columellate, granulate, alveolate and structureless, and permitted comparison with both developing and mature microspore walls. Compared with the previous attempts, we managed to simulate columellate and granulate exines, including lamellate endexine. Conclusions Our results show that simple physico-chemical interactions are able to generate patterns resembling those found in exines, supporting the idea that exine development in nature involves an interplay between the genome and self-assembly.

Self Assembling Nanostructured Delivery Vehicles for Biochemically Reactive Pairs

1994 ◽  
Vol 351 ◽  
Author(s):  
Nir Kossovsky ◽  
A. Gelman ◽  
H.J. Hnatyszyn ◽  
E. Sponsler ◽  
G.-M. Chow
Keyword(s):  
Physical Properties ◽  
Self Assembly ◽  
Materials Science ◽  
Technology Development ◽  
Biological Behavior ◽  
X Ray Diffraction ◽  
Self Assembling ◽  
Transmission Electron ◽  
Carbon Ceramic

ABSTRACTIntrigued by the deceptive simplicity and beauty of macromolecular self-assembly, our laboratory began studying models of self-assembly using solids, glasses, and colloidal substrates. These studies have defined a fundamental new colloidal material for supporting members of a biochemically reactive pair.The technology, a molecular transportation assembly, is based on preformed carbon ceramic nanoparticles and self assembled calcium-phosphate dihydrate particles to which glassy carbohydrates are then applied as a nanometer thick surface coating. This carbohydrate coated core functions as a dehydroprotectant and stabilizes surface immobilized members of a biochemically reactive pair. The final product, therefore, consists of three layers. The core is comprised of the ceramic, the second layer is the dehydroprotectant carbohydrate adhesive, and the surface layer is the biochemically reactive molecule for which delivery is desired.We have characterized many of the physical properties of this system and have evaluated the utility of this delivery technology in vitro and in animal models. Physical characterization has included standard and high resolution transmission electron microscopy, electron and x-ray diffraction and ζ potential analysis. Functional assays of the ability of the system to act as a nanoscale dehydroprotecting delivery vehicle have been performed on viral antigens, hemoglobin, and insulin. By all measures at present, the favorable physical properties and biological behavior of the molecular transportation assembly point to an exciting new interdisciplinary area of technology development in materials science, chemistry and biology.

scholarly journals Optimization of Innovative Three-Dimensionally-Structured Hybrid Vesicles to Improve the Cutaneous Delivery of Clotrimazole for the Treatment of Topical Candidiasis

Pharmaceutics ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 263 ◽  
Author(s):  
Maria Letizia Manca ◽  
Iris Usach ◽  
José Esteban Peris ◽  
Antonella Ibba ◽  
Germano Orrù ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chemical Properties ◽  
Chemical Characterization ◽  
Yeast Cells ◽  
Unilamellar Vesicles ◽  
Transmission Electron ◽  
Physico Chemical

New three-dimensionally-structured hybrid phospholipid vesicles, able to load clotrimazole in a high amount (10 mg/mL), were obtained for the first time in this work by significantly reducing the amount of water (≤10%), which was replaced with a mixture of glycerol and ethanol (≈90%). A pre-formulation study was carried out to evaluate the effect of both the composition of the hydrating medium and the concentration of the phospholipid on the physico-chemical properties of hybrid vesicles. Four different three-dimensionally-structured hybrid vesicles were selected as ideal systems for the topical application of clotrimazole. An extensive physico-chemical characterization performed using transmission electron microscopy (TEM), cryogenic transmission electron microscopy (cryo-TEM), 31P-NMR, and small-angle X-ray scattering (SAXS) displayed the formation of small, multi-, and unilamellar vesicles very close to each other, and was capable of forming a three-dimensional network, which stabilized the dispersion. Additionally, the dilution of the dispersion with water reduced the interactions between vesicles, leading to the formation of single unilamellar vesicles. The evaluation of the in vitro percutaneous delivery of clotrimazole showed an improved drug deposition in the skin strata provided by the three-dimensionally-structured vesicles with respect to the commercial cream (Canesten®) used as a reference. Hybrid vesicles were highly biocompatible and showed a significant antifungal activity in vitro, greater than the commercial cream Canesten®. The antimycotic efficacy of formulations was confirmed by the reduced proliferation of the yeast cells at the site of infection in vivo. In light of these results, clotrimazole-loaded, three-dimensionally-structured hybrid vesicles appear to be one of the most innovative and promising formulations for the treatment of candidiasis infections.

scholarly journals On the Aqueous Solution Behavior of C-Substituted 3,1,2-Ruthenadicarbadodecaboranes

Inorganics ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 91 ◽  
Author(s):  
Marta Gozzi ◽  
Benedikt Schwarze ◽  
Peter Coburger ◽  
Evamarie Hey-Hawkins
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Self Assembly ◽  
Self Assembling ◽  
Vis Spectroscopy ◽  
Assembly Behavior ◽  
Biological Performance ◽  
Type 3

3,1,2-Ruthenadicarbadodecaborane complexes bearing the [C2B9H11]2− (dicarbollide) ligand are robust scaffolds, with exceptional thermal and chemical stability. Our previous work has shown that these complexes possess promising anti-tumor activities in vitro, and tend to form aggregates (or self-assemblies) in aqueous solutions. Here, we report on the synthesis and characterization of four ruthenium(II) complexes of the type [3-(η6-arene)-1,2-R2-3,1,2-RuC2B9H9], bearing either non-polar (R = Me (2–4)) or polar (R = CO2Me (7)) substituents at the cluster carbon atoms. The behavior in aqueous solution of complexes 2, 7 and the parent unsubstituted [3-(η6-p-cymene)-3,1,2-RuC2B9H11] (8) was investigated via UV-Vis spectroscopy, mass spectrometry and nanoparticle tracking analysis (NTA). All complexes showed spontaneous formation of self-assemblies (108–109 particles mL−1), at low micromolar concentration, with high polydispersity. For perspective applications in medicine, there is thus a strong need for further characterization of the spontaneous self-assembly behavior in aqueous solutions for the class of neutral metallacarboranes, with the ultimate scope of finding the optimal conditions for exploiting this self-assembling behavior for improved biological performance.

scholarly journals Virus assembly occurs following a pH- or Ca 2+ -triggered switch in the thermodynamic attraction between structural protein capsomeres

2009 ◽  
Vol 7 (44) ◽  
pp. 409-421 ◽  
Author(s):  
Yap P. Chuan ◽  
Yuan Y. Fan ◽  
Linda H. L. Lua ◽  
Anton P. J. Middelberg
Keyword(s):  
Self Assembly ◽  
Virus Assembly ◽  
Chemical Change ◽  
Second Virial Coefficient ◽  
Direct Proof ◽  
Viral Assembly ◽  
Structural Protein ◽  
Salting Out ◽  
Self Assembling

Viral self-assembly is of tremendous virological and biomedical importance. Although theoretical and crystallographic considerations suggest that controlled conformational change is a fundamental regulatory mechanism in viral assembly, direct proof that switching alters the thermodynamic attraction of self-assembling components has not been provided. Using the VP1 protein of polyomavirus, we report a new method to quantitatively measure molecular interactions under conditions of rapid protein self-assembly. We show, for the first time, that triggering virus capsid assembly through biologically relevant changes in Ca 2+ concentration, or pH, is associated with a dramatic increase in the strength of protein molecular attraction as quantified by the second virial coefficient ( B 22 ). B 22 decreases from −2.3 × 10 −4 mol ml g −2 (weak protein–protein attraction) to −2.4 × 10 −3 mol ml g −2 (strong protein attraction) for metastable and Ca 2+ -triggered self-assembling capsomeres, respectively. An assembly-deficient mutant (VP1CΔ63) is conversely characterized by weak protein–protein repulsion independently of chemical change sufficient to cause VP1 assembly. Concomitant switching of both VP1 assembly and thermodynamic attraction was also achieved by in vitro changes in ammonium sulphate concentration, consistent with protein salting-out behaviour. The methods and findings reported here provide new insight into viral assembly, potentially facilitating the development of new antivirals and vaccines, and will open the way to a more fundamental physico-chemical description of complex protein self-assembly systems.

Evolving Reaction-Diffusion Ecosystems with Self-Assembling Structures in Thin Films

1998 ◽  
Vol 4 (1) ◽  
pp. 25-40 ◽  
Author(s):  
Jens Breyer ◽  
Jörg Ackermann ◽  
John McCaskill
Keyword(s):  
Self Assembly ◽  
Flexible Structures ◽  
Reaction Diffusion ◽  
In Vitro Evolution ◽  
Spatially Resolved ◽  
Self Assembling ◽  
Artificial Dna ◽  
Additional Stabilization ◽  
Artificial Chemistries

Recently, new types of coupled isothermal polynucleotide amplification reactions for the investigation of in vitro evolution have been established that are based on the multi-enzyme 3SR reaction. Microstructured thin-film open bioreactors have been constructed in our laboratory to run these reactions spatially resolved in flow experiments. Artificial DNA/RNA chemistries close to the in vitro biochemistry of these systems have been developed, which we have studied in computer simulations in configurable hardware (NGEN). These artificial chemistries are described on the level of individual polynucleotide molecules, each with a defined sequence, and their complexes. The key feature of spatial pattern formation provides a weak stabilization of cooperative catalytic properties of the evolving molecules. Of great interest is the step to include extended self-assembly processes of flexible structures—allowing the additional stabilization of cooperation through semipermeable, flexible, self-organizing membrane boundaries. We show how programmable matter simulations of experimentally relevant molecular in vitro evolution can be extended to include the influence of self-assembling flexible membranes.

Copolymer Nanoparticles Prepared by Self-Assembly of Poly(ethylene glycol) and Poly-γ-Glutamic Acid and its Characteristics

2013 ◽  
Vol 662 ◽  
pp. 136-139
Author(s):  
Ge Yang ◽  
Ke Shuai Lu ◽  
Xue Yan Su
Keyword(s):  
Ethylene Glycol ◽  
Glutamic Acid ◽  
Size Distribution ◽  
Self Assembly ◽  
Aqueous Media ◽  
Poly Ethylene Glycol ◽  
Polyelectrolyte Complexes ◽  
Self Assembling ◽  
Transmission Electron ◽  
Poly Ethylene

The paper describes the preparation and characterization of novel biodegradable nanoparticles based on self-assembly of poly-gamma-glutamic acid (γ-PGA) and poly(ethylene glycol) (PEG). The nanosystems were stable in aqueous media at low pH conditions. Solubility of the systems was determined by turbidity measurements. The particle size and the size distribution of the polyelectrolyte complexes were identified by dynamic lightscattering and transmission electron microscopy.It was found that the size and size distribution of the nanosystems depends on the concentrations of γ-PGA and PEG solutions and their ratio as well as on the pH of the mixture and the order of addition. The diameter of individual particles was in the range of 30–270 nm. measured by TEM, and the average hydrodynamic diameters were between 130 and 300 nm. These biodegradable, self-assembling stable nanocomplexes might be useful for several biomedical applications.

scholarly journals Lipid membranes trigger misfolding and self-assembly of amyloid β 42 protein into aggregates

2019 ◽  
Author(s):  
Siddhartha Banerjee ◽  
Mohtadin Hashemi ◽  
Karen Zagorski ◽  
Yuri L. Lyubchenko
Keyword(s):  
Self Assembly ◽  
Lipid Membranes ◽  
Membrane Surface ◽  
Amyloid Β ◽  
Test Tube ◽  
Aggregation Process ◽  
Self Assembling ◽  
Nanoscale Aggregates

AbstractThe assembly of polypeptides and proteins into nanoscale aggregates is a phenomenon observed in a vast majority of proteins. Importantly, aggregation of amyloid β (Aβ) proteins is considered as a major cause for the development of Alzheimer’s disease. The process depends on various conditions and typical test-tube experiments require high protein concentration that complicates the translation of results obtained in vitro to understanding the aggregation process in vivo. Here we demonstrate that Aβ42 monomers at the membrane bilayer are capable of self-assembling into aggregates at physiologically low concentrations, and the membrane in this aggregation process plays a role of a catalyst. We applied all-atom molecular dynamics to demonstrate that the interaction with the membrane surface dramatically changes the conformation of Aβ42 protein. As a result, the misfolded Aβ42 rapidly assembles into dimers, trimers and tetramers, so the on-surface aggregation is the mechanism by which amyloid oligomers are produced and spread.

scholarly journals Biocatalysis of d,l-Peptide Nanofibrillar Hydrogel

Molecules ◽  
2020 ◽  
Vol 25 (13) ◽  
pp. 2995 ◽  
Author(s):  
Tiziano Carlomagno ◽  
Maria C. Cringoli ◽  
Slavko Kralj ◽  
Marina Kurbasic ◽  
Paolo Fornasiero ◽  
...  
Keyword(s):  
Self Assembly ◽  
Solid Phase ◽  
Building Blocks ◽  
Cd Spectroscopy ◽  
Tem Analysis ◽  
Design Rules ◽  
Self Assembling ◽  
Transmission Electron ◽  
Oscillatory Rheometry ◽  
The Many

Self-assembling peptides are attracting wide interest as biodegradable building blocks to achieve functional nanomaterials that do not persist in the environment. Amongst the many applications, biocatalysis is gaining momentum, although a clear structure-to-activity relationship is still lacking. This work applied emerging design rules to the heterochiral octapeptide sequence His–Leu–DLeu–Ile–His–Leu–DLeu–Ile for self-assembly into nanofibrils that, at higher concentration, give rise to a supramolecular hydrogel for the mimicry of esterase-like activity. The peptide was synthesized by solid-phase and purified by HPLC, while its identity was confirmed by 1H-NMR and electrospray ionization (ESI)-MS. The hydrogel formed by this peptide was studied with oscillatory rheometry, and the supramolecular behavior of the peptide was investigated with transmission electron microscopy (TEM) analysis, circular dichroism (CD) spectroscopy, thioflavin T amyloid fluorescence assay, and attenuated total reflectance (ATR) Fourier-transform infrared (FT-IR) spectroscopy. The biocatalytic activity was studied by monitoring the hydrolysis of p-nitrophenyl acetate (pNPA) at neutral pH, and the reaction kinetics followed an apparent Michaelis–Menten model, for which a Lineweaver–Burk plot was produced to determine its enzymatic parameters for a comparison with the literature. Finally, LC–MS analysis was conducted on a series of experiments to evaluate the extent of, if any, undesired peptide acetylation at the N-terminus. In conclusion, we provide new insights that allow gaining a clearer picture of self-assembling peptide design rules for biocatalysis.

Possible Physico-Chemical Processes in Human Dentin Caries

1987 ◽  
Vol 66 (8) ◽  
pp. 1356-1359 ◽  
Author(s):  
G. Daculsi ◽  
R.Z. LeGeros ◽  
A. Jean ◽  
B. Kerebel
Keyword(s):  
Precipitation Method ◽  
Molar Ratios ◽  
Ultrastructural Studies ◽  
Dentin Caries ◽  
Transmission Electron ◽  
Physico Chemical ◽  
Human Dentin ◽  
Chronological Sequence ◽  
Chemical Events

This study correlated ultrastructural observations on the presence of beta-tricalcium phosphate (β-TCP) in arrested dentin caries with physico-chemical observations on the in vitro formation of Mg-substituted β-TCP. The ultrastructural studies were made using high-resolution transmission electron microscopy (TEM) with the capability of microdiffraction and microanalysis on sites less than 10 nm in diameter. Mg-substituted β-TCP was obtained, by a precipitation method, from solutions with Mg/Ca molar ratios of 5/95 and higher. Such correlation led to the postulation of a possible chronological sequence of physico-chemical events occurring at the crystal level during the progress and arrest of caries in human dentin. It is suggested that the initial mechanism for the observed occurrence of large crystals of Mg-substituted β-TCP and of apatite in the tubule lumen is due to the dissolution of the dentin mineral (a CO 3- and Mg-rich calcium OH-apatite) and reprecipitation of Mg-substituted β-TCP, followed by that of CO3- and Mg-poor apatite.

Controlling neuronal growth and connectivity via directed self-assembly of proteins

2013 ◽  
Vol 1498 ◽  
pp. 207-212
Author(s):  
Daniel Rizzo ◽  
Ross Beighley ◽  
James D. White ◽  
Cristian Staii
Keyword(s):  
Self Assembly ◽  
Gold Surface ◽  
Nerve Tissue ◽  
3 Dimensional ◽  
Force Microscopy ◽  
Self Assembling ◽  
Atomic Force ◽  
Will Self ◽  
Neuron Growth

ABSTRACTMaterials that offer the ability to influence tissue regeneration are of vital importance to the field of Tissue Engineering. Because valid 3-dimensional scaffolds for nerve tissue are still in development, advances with 2-dimensional surfaces in vitro are necessary to provide a complete understanding of controlling regeneration. Here we present a method for controlling nerve cell growth on Au electrodes using Atomic Force Microscopy -aided protein assembly. After coating a gold surface in a self-assembling monolayer of alkanethiols, the Atomic Force Microscope tip can be used to remove regions of the self-assembling monolayer in order to produce well-defined patterns. If this process is then followed by submersion of the sample into a solution containing neuro-compatible proteins, they will self assemble on these exposed regions of gold, creating well-specified regions for promoted neuron growth.

Sign in / Sign up

Export Citation Format

Share Document