scholarly journals Colony-like Protocell Superstructures

2021 ◽  
Author(s):  
Karolina Spustova ◽  
Chinmay Katke ◽  
Esteban Pedrueza Villalmanzo ◽  
Ruslan Ryskulov ◽  
C. Nadir Kaplan ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
Critical Length ◽  
Solid Surfaces ◽  
Strand Displacement ◽  
Shape Transformation ◽  
Lipid World ◽  
Membrane Envelope ◽  
Membrane Bending ◽  
World Hypothesis ◽  
Aluminum Surfaces

AbstractWe report the formation, growth, and dynamics of model protocell superstructures on solid surfaces, resembling single cell colonies. These structures, consisting of several layers of lipidic compartments enveloped in a dome-shaped outer lipid bilayer, emerged as a result of spontaneous shape transformation of lipid agglomerates deposited on thin film aluminum surfaces. Collective protocell structures were observed to be mechanically more stable compared to isolated spherical compartments. We show that the model colonies encapsulate DNA and accommodate non-enzymatic, strand displacement DNA reactions. The membrane envelope is able to disassemble and expose individual daughter protocells, which can migrate and attach via nano-tethers to distant surface locations, while maintaining their encapsulated contents. Some colonies feature ‘exo-compartments’, which spontaneously extend out of the enveloping bilayer, internalize DNA, and merge again with the superstructure. A continuum elastohydrodynamic theory that we developed reveals that the subcompartment formation must be governed by attractive van der Waals (vdW) interactions between the membrane and surface. The balance between membrane bending and vdW interactions yields a critical length scale of 273 nm, above which the membrane invaginations can form subcompartments. The findings support our hypotheses that in extension of the ‘lipid world hypothesis’, protocells may have existed in the form of colonies, potentially benefiting from the increased mechanical stability provided by a superstructure.

scholarly journals Spontaneous formation of prebiotic compartment colonies on Hadean Earth and pre-Noachian Mars

2021 ◽  
Author(s):  
Elif Senem Koksal ◽  
Inga Poldsalu ◽  
Henrik Friis ◽  
Stephen Mojzsis ◽  
Martin Bizarro ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Physical Interaction ◽  
Shape Transformation ◽  
Naturally Occurring ◽  
Dna Strand Displacement ◽  
Lipid World ◽  
Displacement Reactions ◽  
Freely Suspended ◽  
Dna Strand ◽  
World Hypothesis

The primitive cells that emerged at the origin of life are commonly viewed as spherical biosurfactant shells, freely suspended in aqueous media (1-3). This model explains initial, but not subsequent events in the development process towards structured protocells. Taking into consideration the involvement of naturally occurring surfaces, which were abundant on the early Earth (4), we report feasible and productive pathways for the development of primitive cells. Surfaces intrinsically possess energy, easily utilized by the interfacing amphiphiles, such as lipids, to attain self-organization and spontaneous transformations (5-7). We show that the physical interaction of phospholipid pools with 20 Hadean Earth analogue materials as well as a Martian meteorite composed of fused regolith representing the ancient crust of Mars, consistently lead to the shape transformation and autonomous formation of surfactant compartment assemblies. Dense, colony-like protocell populations grow from these lipid deposits, predominantly at the grain boundaries or cleavages of the investigated natural surfaces, and remain there for several days. The model protocells in our study are able to autonomously develop, transform and pseudo-divide, and encapsulate RNA as well as DNA. We also demonstrate that they can accommodate non-enzymatic, DNA strand displacement reactions. Our findings suggest a feasible route towards the transformation from non-living to living entities, and provide fresh support for the 'Lipid World' hypothesis (8).

Fabrication of Superhydrophobic Aluminum Surfaces Using Modified Nanoparticles and Ionizable Surfactants

2021 ◽  
pp. 2150035
Author(s):  
Bahram Abedi Ravan ◽  
Akbar Cheraghi
Keyword(s):  
Annealing Temperature ◽  
Mechanical Stability ◽  
Sea Water ◽  
Industrial Applications ◽  
Wet Etching ◽  
Etching Time ◽  
Water Contact ◽  
Solvent Type ◽  
Mechanical Durability ◽  
Aluminum Surfaces

In this study, plates of aluminum are made superhydrophobic via wet etching followed by deposition of nanostructure and microstructure. Etched surfaces are coated with modified nanoalumina using an ionizable surfactant. Key parameters governing the hydrophobicity such as type of the etching solvent, type of the surfactant, etching time, nanoparticle size distribution, surfactant concentration and annealing temperature are investigated. Infrared spectroscopy (IR), dynamic light scattering (DLS), scanning electron microscopy (SEM) and water contact angle (WCA) measurements are used to characterize the treated surfaces. A WCA greater than 150∘ is obtained and in order to estimate the efficiency and mechanical durability of the coatings the samples are tested in emulated sea-water. Water jet tests prove the mechanical stability of the samples. Our fabrication method results in good hydrophobicity and self-cleaning behavior of the Al surface and the obtained results may be useful for industrial applications.

scholarly journals Binding energy and mechanical stability of two parallel and crossing carbon nanotubes

2015 ◽  
Vol 471 (2180) ◽  
pp. 20150229 ◽  
Author(s):  
Junhua Zhao ◽  
Yue Jia ◽  
Ning Wei ◽  
Timon Rabczuk
Keyword(s):  
Carbon Nanotubes ◽  
Binding Energy ◽  
Mechanical Stability ◽  
Critical Length ◽  
High Accuracy ◽  
Molecular Dynamics Calculations ◽  
Continuum Modelling ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
The Continuum

The binding energy between two parallel (and two crossing) single-walled (and multi-walled) carbon nanotubes (CNTs) is obtained by continuum modelling of the van der Waals interaction between them. The dependence of the binding energy on their diameters, number of walls and crossing angles is systematically analysed. The critical length for the mechanical stability and adhesion of the CNTs is determined by the function of E i I i , h and γ , where E i I i , h and γ are the CNTs bending stiffness, distance and binding energy between them, respectively. Checking against full atom molecular dynamics calculations show that the continuum solution has high accuracy. The established analytical solutions should be of great help for designing nanoelectromechanical devices.

scholarly journals Possible Roles of Amphiphilic Molecules in the Origin of Biological Homochirality

Symmetry ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 966 ◽  
Author(s):  
Nozomu Suzuki ◽  
Yutaka Itabashi
Keyword(s):  
Physical Properties ◽  
Origin Of Life ◽  
Supramolecular Assembly ◽  
Spontaneous Formation ◽  
Amphiphilic Molecules ◽  
Lipid World ◽  
The Origin Of Life ◽  
Compositional Information ◽  
World Hypothesis ◽  
Biological Homochirality

A review. The question of homochirality is an intriguing problem in the field of chemistry, and is deeply related to the origin of life. Though amphiphiles and their supramolecular assembly have attracted less attention compared to biomacromolecules such as RNA and proteins, the lipid world hypothesis sheds new light on the origin of life. This review describes how amphiphilic molecules are possibly involved in the scenario of homochirality. Some prebiotic conditions relevant to amphiphilic molecules will also be described. It could be said that the chiral properties of amphiphilic molecules have various interesting features such as compositional information, spontaneous formation, the ability to exchange components, fission and fusion, adsorption, and permeation. This review aims to clarify the roles of amphiphiles regarding homochirality, and to determine what kinds of physical properties of amphiphilic molecules could have played a role in the scenario of homochirality.

scholarly journals Lipid-Assisted Polymerization of Nucleotides

Life ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 83
Author(s):  
Felix Olasagasti ◽  
Sudha Rajamani
Keyword(s):  
Enzymatic Synthesis ◽  
Origins Of Life ◽  
Lipid World ◽  
New Apparatus ◽  
Geothermal Environments ◽  
World Hypothesis

In addition to being one of the proponents of the “Lipid World hypothesis”, David Deamer, together with other colleagues, pioneered studies involving formation of RNA-like oligomers from their ‘non-activated’, prebiotically plausible monomeric moieties. In particular, the pioneering work in this regard was a publication from 2008 in Origins of Life and Evolution of Biospheres, The Journal of the International Astrobiology Society, wherein we described the formation of RNA-like oligomers from nucleoside 5’-monophosphates. In that study, we had simulated a terrestrial geothermal environment, a niche that is thought to have facilitated the prebiotic non-enzymatic synthesis of polynucleotides. We showed that a mixture of lipids and non-activated mononucleotides resulted in the formation of relatively long strands of RNA-like polymers when subjected to repeated cycles of dehydration and rehydration (DH-RH). Since 2008, terrestrial geothermal niches and DH-RH conditions have been explored in the context of several other prebiotic processes. In this article, we review the work that we and other researchers have carried out since then in this line of research, including the development of new apparatus to carry out the simulation of prebiotic terrestrial geothermal environments.

scholarly journals Non-enzymatic primer extension with strand displacement

2019 ◽  
Author(s):  
Lijun Zhou ◽  
Seohyun Chris Kim ◽  
Katherine H. Ho ◽  
Derek K. O’Flaherty ◽  
Constantin Giurgiu ◽  
...  
Keyword(s):  
Rna World ◽  
Genetic Material ◽  
Kinetic Studies ◽  
Single Step ◽  
Primer Extension ◽  
Branch Migration ◽  
Strand Displacement ◽  
World Hypothesis ◽  
Self Replication ◽  
Rna World Hypothesis

AbstractNon-enzymatic RNA self-replication is integral to the ‘RNA World’ hypothesis. Despite considerable progress in non-enzymatic template copying, true replication remains challenging due to the difficulty of separating the strands of the product duplex. Here, we report a prebiotically plausible solution to this problem in which short ‘invader’ oligonucleotides unwind an RNA duplex through a toehold/branch migration mechanism, allowing non-enzymatic primer extension on a template that was previously occupied by its complementary strand. Kinetic studies of single-step reactions suggest that following invader binding, branch migration results in a 2:3 partition of the template between open and closed states. Finally, we demonstrate continued primer extension with strand displacement by employing activated 3′-aminonucleotides, a more reactive proxy for ribonucleotides. Our study suggests that complete cycles of non-enzymatic replication of the primordial genetic material may have been catalyzed by short RNA oligonucleotides.

Quantitative analysis of in situ straining experiments in the case of strong frictional forces

1978 ◽  
Vol 36 (1) ◽  
pp. 570-571
Author(s):  
F. Louchet ◽  
L.P. Kubin
Keyword(s):  
Strain Rate ◽  
Radiation Effects ◽  
Dislocation Line ◽  
Critical Length ◽  
Local Strain ◽  
Local Flow ◽  
Double Kink ◽  
Dislocation Densities ◽  
Frictional Forces ◽  
Local Strain Rate

Investigation of frictional forces -Experimental techniques and working conditions in the high voltage electron microscope have already been described (1). Care has been taken in order to minimize both surface and radiation effects under deformation conditions.Dislocation densities and velocities are measured on the records of the deformation. It can be noticed that mobile dislocation densities can be far below the total dislocation density in the operative system. The local strain-rate can be deduced from these measurements. The local flow stresses are deduced from the curvature radii of the dislocations when the local strain-rate reaches the values of ∿ 10-4 s-1.For a straight screw segment of length L moving by double-kink nucleation between two pinning points, the velocity is :where ΔG(τ) is the activation energy and lc the critical length for double-kink nucleation. The term L/lc takes into account the number of simultaneous attempts for double-kink nucleation on the dislocation line.

An improved design for an Scanning Tunnelling Microscope (STM) for use in a Transmission Electron Microscope (TEM)

1991 ◽  
Vol 49 ◽  
pp. 384-385
Author(s):  
W.K. Lo ◽  
J.C.H. Spence
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Mechanical Stability ◽  
Scanning Tunnelling Microscope ◽  
Reflection Mode ◽  
Specimen Holder ◽  
Transmission Electron ◽  
Scanning Tunnelling ◽  
Improved Design

An improved design for a combination Scanning Tunnelling Microscope/TEM specimen holder is presented. It is based on earlier versions which have been used to test the usefulness of such a device. As with the earlier versions, this holder is meant to replace the standard double-tilt specimen holder of an unmodified Philips 400T TEM. It allows the sample to be imaged simultaneously by both the STM and the TEM when the TEM is operated in the reflection mode (see figure 1).The resolution of a STM is determined by its tip radii as well as its stability. This places strict limitations on the mechanical stability of the tip with respect to the sample. In this STM the piezoelectric tube scanner is rigidly mounted inside the endcap of the STM holder. The tip coarse approach to the sample (z-direction) is provided by an Inchworm which is located outside the TEM vacuum.

Experiments with a scanning tunneling microscope (STM) mounted in a scanning electron microscope (SEM)

1986 ◽  
Vol 44 ◽  
pp. 636-639
Author(s):  
Oliver C. Wells ◽  
Mark E. Welland
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Mechanical Stability ◽  
Tunneling Current ◽  
Feedback System ◽  
Scanning Tunneling ◽  
Surface Profiling ◽  
Close Proximity ◽  
Metal Tip ◽  
Scanning Electron

Scanning tunneling microscopes (STM) exist in two versions. In both of these, a pointed metal tip is scanned in close proximity to the specimen surface by means of three piezos. The distance of the tip from the sample is controlled by a feedback system to give a constant tunneling current between the tip and the sample. In the low-end STM, the system has a mechanical stability and a noise level to give a vertical resolution of between 0.1 nm and 1.0 nm. The atomic resolution STM can show individual atoms on the surface of the specimen.A low-end STM has been put into the specimen chamber of a scanning electron microscope (SEM). The first objective was to investigate technological problems such as surface profiling. The second objective was for exploratory studies. This second objective has already been achieved by showing that the STM can be used to study trapping sites in SiO2.

Electron microscopy of keratinocytes cultured on a collagen substrate used as an allograft for the treatment of chronic wounds

1992 ◽  
Vol 50 (2) ◽  
pp. 1104-1105
Author(s):  
Debby A. Jennings ◽  
Michael J. Morykwas ◽  
Louis C. Argenta
Keyword(s):  
Electron Microscopy ◽  
Cell Suspension ◽  
Single Cell ◽  
Chronic Wounds ◽  
Mechanical Stability ◽  
Uv Light ◽  
Type I ◽  
Single Cell Suspension ◽  
Collagen Substrate ◽  
Dermal Collagen

Grafts of cultured allogenic or autogenic keratlnocytes have proven to be an effective treatment of chronic wounds and burns. This study utilized a collagen substrate for keratinocyte and fibroblast attachment. The substrate provided mechanical stability and augmented graft manipulation onto the wound bed. Graft integrity was confirmed by light and transmission electron microscopy.Bovine Type I dermal collagen sheets (100 μm thick) were crosslinked with 254 nm UV light (13.5 Joules/cm2) to improve mechanical properties and reduce degradation. A single cell suspension of third passage neonatal foreskin fibroblasts were plated onto the collagen. Five days later, a single cell suspension of first passage neonatal foreskin keratinocytes were plated on the opposite side of the collagen. The grafts were cultured for one month.The grafts were fixed in phosphate buffered 4% formaldehyde/1% glutaraldehyde for 24 hours. Graft pieces were then washed in 0.13 M phosphate buffer, post-fixed in 1% osmium tetroxide, dehydrated, and embedded in Polybed 812.

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