scholarly journals Super-resolution imaging of highly curved membrane structures in giant vesicles encapsulating molecular condensates

2021 ◽  
Author(s):  
Ziliang Zhao ◽  
Debjit Roy ◽  
Jan Steinkuehler ◽  
Tom Robinson ◽  
Reinhard Lipowsky ◽  
...  
Keyword(s):  
Contact Angle ◽  
Super Resolution ◽  
Contact Angles ◽  
Stimulated Emission ◽  
Spontaneous Curvature ◽  
Molecular Crowding ◽  
Membrane Structures ◽  
Giant Vesicles ◽  
Curved Membrane ◽  
Intrinsic Contact Angle

Molecular crowding is an inherent feature of the cell interior. Synthetic cells as provided by giant unilamellar vesicles (GUVs) encapsulating macromolecules (polyethylene-glycol and dextran) represent an excellent mimetic system to study membrane transformations associated with molecular crowding and protein condensation. Similarly to cells, such GUVs loaded with macromolecules exhibit highly curved structures such as internal nanotubes. In addition, upon liquid-liquid phase separation as inside living cells, the membrane of GUVs encapsulating an aqueous two-phase system deforms to form apparent kinks at the contact line of the interface between the two aqueous phases. These structures, nanotubes and kinks, have dimensions below optical resolution and if resolved, can provide information about material properties such as membrane spontaneous curvature and intrinsic contact angle describing the wettability contrast of the encapsulated phases to the membrane. Previous experimental studies were based on conventional optical microscopy which cannot resolve these membrane and wetting proper-ties. Here, we studied these structures with super-resolution microscopy, namely stimulated emission depletion (STED) microscopy, together with microfluidic manipulation. We demonstrate the cylindrical nature of the nanotubes with unprecedented detail based on the superior resolution of STED and automated data analysis. The spontaneous curvature deduced from the nanotube diameters is in excellent agreement with theoretical predictions. Furthermore, we were able to resolve the membrane 'kink' structure as a smoothly curved membrane demonstrating the existence of the intrinsic contact angle. We find very good agreement between the directly measured values and the theoretically predicted ones based on the apparent contact angles on the micrometer scale. During different stages of cellular events, biomembranes undergo a variety of shape transformations such as the formation of buds and nanotubes regulated by membrane necks. We demonstrate that these highly curved membrane structures are amenable to STED imaging and show that such studies provide important insights in the membrane properties and interactions underlying cellular activities.

scholarly journals Super‐resolution imaging of highly curved membrane structures in giant vesicles encapsulating molecular condensates

2021 ◽  
pp. 2106633
Author(s):  
Ziliang Zhao ◽  
Debjit Roy ◽  
Jan Steinkühler ◽  
Tom Robinson ◽  
Reinhard Lipowsky ◽  
...  
Keyword(s):  
Super Resolution ◽  
Membrane Structures ◽  
Giant Vesicles ◽  
Resolution Imaging ◽  
Curved Membrane

scholarly journals Illuminating the Impact of Nanoparticle Size and Surface Chemistry on Interfacial Position

2020 ◽  
Author(s):  
Emma Giakoumatos ◽  
Antonio Aloi ◽  
Ilja Voets
Keyword(s):  
Contact Angle ◽  
Particle Size ◽  
Surface Chemistry ◽  
Particle Surface ◽  
Particle Diameter ◽  
Super Resolution ◽  
Contact Angles ◽  
Pickering Emulsions ◽  
Microscopy Technique ◽  
The Impact

In this manuscript we begin by preparing bulk Pickering emulsions of water:octanol at varying aqueous pH values, using ionizable carboxyl polystyrene nanoparticles of 320 nm and 810 nm diameter. Remarkably we observe two emulsion phase inversions, one resulting from an increase in pH and a second due to an increase in particle size. To illuminate the mechanism of the macroscopic phase inversion, we turn to the super resolution microscopy technique <i>interface Point Accumulation for Imaging and Nanoscale Topography</i> (iPAINT) to measure in-situ the contact angles of single carboxyl polystyrene particles at the water:octanol interface. Importantly, we identify a significant decrease in contact angle over the increase of pH and particle diameter, respectively. Additionally, the non-negligible dependence of contact angle on particle size was shown to hold regardless of particle surface chemistry.

scholarly journals Illuminating the Impact of Nanoparticle Size and Surface Chemistry on Interfacial Position

2020 ◽  
Author(s):  
Emma Giakoumatos ◽  
Antonio Aloi ◽  
Ilja Voets
Keyword(s):  
Contact Angle ◽  
Particle Size ◽  
Surface Chemistry ◽  
Particle Surface ◽  
Particle Diameter ◽  
Super Resolution ◽  
Contact Angles ◽  
Pickering Emulsions ◽  
Microscopy Technique ◽  
The Impact

In this manuscript we begin by preparing bulk Pickering emulsions of water:octanol at varying aqueous pH values, using ionizable carboxyl polystyrene nanoparticles of 320 nm and 810 nm diameter. Remarkably we observe two emulsion phase inversions, one resulting from an increase in pH and a second due to an increase in particle size. To illuminate the mechanism of the macroscopic phase inversion, we turn to the super resolution microscopy technique <i>interface Point Accumulation for Imaging and Nanoscale Topography</i> (iPAINT) to measure in-situ the contact angles of single carboxyl polystyrene particles at the water:octanol interface. Importantly, we identify a significant decrease in contact angle over the increase of pH and particle diameter, respectively. Additionally, the non-negligible dependence of contact angle on particle size was shown to hold regardless of particle surface chemistry.

Curved membrane structures induced by native lipids in giant vesicles

2021 ◽  
Author(s):  
Karthika S Nair ◽  
Neethu B Raj ◽  
K Madhavan Nampoothiri ◽  
Gayathri Mohanan ◽  
Silvia Acosta-Gutiérrez ◽  
...  
Keyword(s):  
Membrane Structures ◽  
Giant Vesicles ◽  
Curved Membrane

scholarly journals Super Resolution Imaging of Highly Curved Membrane Structures in Giant Unilamellar Vesicles Encapsulating Polymer Solutions

2018 ◽  
Vol 114 (3) ◽  
pp. 100a-101a ◽  
Author(s):  
Ziliang Zhao ◽  
Debjit Roy ◽  
Jan Steinkühler ◽  
Tom Robinson ◽  
Roland Knorr ◽  
...  
Keyword(s):  
Polymer Solutions ◽  
Super Resolution ◽  
Giant Unilamellar Vesicles ◽  
Membrane Structures ◽  
Unilamellar Vesicles ◽  
Resolution Imaging ◽  
Curved Membrane

scholarly journals Comparing Super-Resolution Microscopy Techniques to Analyze Chromosomes

2021 ◽  
Vol 22 (4) ◽  
pp. 1903
Author(s):  
Ivona Kubalová ◽  
Alžběta Němečková ◽  
Klaus Weisshart ◽  
Eva Hřibová ◽  
Veit Schubert
Keyword(s):  
Single Molecule ◽  
Imaging Techniques ◽  
Chromatin Condensation ◽  
Super Resolution ◽  
Stimulated Emission ◽  
Wide Field ◽  
Structured Illumination Microscopy ◽  
Metaphase Chromosomes ◽  
Localization Microscopy ◽  
Super Resolution Microscopy

The importance of fluorescence light microscopy for understanding cellular and sub-cellular structures and functions is undeniable. However, the resolution is limited by light diffraction (~200–250 nm laterally, ~500–700 nm axially). Meanwhile, super-resolution microscopy, such as structured illumination microscopy (SIM), is being applied more and more to overcome this restriction. Instead, super-resolution by stimulated emission depletion (STED) microscopy achieving a resolution of ~50 nm laterally and ~130 nm axially has not yet frequently been applied in plant cell research due to the required specific sample preparation and stable dye staining. Single-molecule localization microscopy (SMLM) including photoactivated localization microscopy (PALM) has not yet been widely used, although this nanoscopic technique allows even the detection of single molecules. In this study, we compared protein imaging within metaphase chromosomes of barley via conventional wide-field and confocal microscopy, and the sub-diffraction methods SIM, STED, and SMLM. The chromosomes were labeled by DAPI (4′,6-diamidino-2-phenylindol), a DNA-specific dye, and with antibodies against topoisomerase IIα (Topo II), a protein important for correct chromatin condensation. Compared to the diffraction-limited methods, the combination of the three different super-resolution imaging techniques delivered tremendous additional insights into the plant chromosome architecture through the achieved increased resolution.

scholarly journals Influence of moisture content on the contact angle and surface tension measured on birch wood surfaces

2021 ◽  
Author(s):  
Rami Benkreif ◽  
Fatima Zohra Brahmia ◽  
Csilla Csiha
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Moisture Content ◽  
Solid Wood ◽  
Contact Angles ◽  
Surface Moisture ◽  
Wood Coatings ◽  
The Relationship ◽  
Wood Surfaces

AbstractSurface tension of solid wood surfaces affects the wettability and thus the adhesion of various adhesives and wood coatings. By measuring the contact angle of the wood, the surface tension can be calculated based on the Young-Dupré equation. Several publications have reported on contact angle measured with different test liquids, under different conditions. Results can only be compared if the test conditions are similar. While the roles of the drop volume, image shooting time etc., are widely recognized, the role of the wood surface moisture content (MC) is not evaluated in detail. In this study, the effect of wood moisture content on contact angle values, measured with distilled water and diiodomethane, on sanded birch (Betula pendula) surfaces was investigated, in order to find the relationship between them. With increasing MC from approximately 6% to 30%, increasing contact angle (decreasing surface tension) values were measured according to a logarithmic function. The function makes possible the calculation of contact angles that correspond to different MCs.

scholarly journals Biomimetic Approach for the Elaboration of Highly Hydrophobic Surfaces: Study of the Links between Morphology and Wettability

Biomimetics ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 38
Author(s):  
Quentin Legrand ◽  
Stephane Benayoun ◽  
Stephane Valette
Keyword(s):  
Contact Angle ◽  
Ginkgo Biloba ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Textured Surfaces ◽  
Replication Process ◽  
Wetting Behavior ◽  
Static Contact ◽  
Biomimetic Approach ◽  
Highly Hydrophobic

This investigation of morphology-wetting links was performed using a biomimetic approach. Three natural leaves’ surfaces were studied: two bamboo varieties and Ginkgo Biloba. Multiscale surface topographies were analyzed by SEM observations, FFT, and Gaussian filtering. A PDMS replicating protocol of natural surfaces was proposed in order to study the purely morphological contribution to wetting. High static contact angles, close to 135∘, were measured on PDMS replicated surfaces. Compared to flat PDMS, the increase in static contact angle due to purely morphological contribution was around 20∘. Such an increase in contact angle was obtained despite loss of the nanometric scale during the replication process. Moreover, a significant decrease of the hysteresis contact angle was measured on PDMS replicas. The value of the contact angle hysteresis moved from 40∘ for flat PDMS to less than 10∘ for textured replicated surfaces. The wetting behavior of multiscale textured surfaces was then studied in the frame of the Wenzel and Cassie–Baxter models. Whereas the classical laws made it possible to describe the wetting behavior of the ginkgo biloba replications, a hierarchical model was developed to depict the wetting behavior of both bamboo species.

scholarly journals Is contact angle a cause or an effect? – A cautionary tale

2020 ◽  
Vol 146 ◽  
pp. 03004
Author(s):  
Douglas Ruth
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Angles ◽  
Two Dimensions ◽  
Experimental Results ◽  
Flow In Porous Media ◽  
Two Dimensional ◽  
Wide Range ◽  
Fluid Drop ◽  
Surrounding Fluid

The most influential parameter on the behavior of two-component flow in porous media is “wettability”. When wettability is being characterized, the most frequently used parameter is the “contact angle”. When a fluid-drop is placed on a solid surface, in the presence of a second, surrounding fluid, the fluid-fluid surface contacts the solid-surface at an angle that is typically measured through the fluid-drop. If this angle is less than 90°, the fluid in the drop is said to “wet” the surface. If this angle is greater than 90°, the surrounding fluid is said to “wet” the surface. This definition is universally accepted and appears to be scientifically justifiable, at least for a static situation where the solid surface is horizontal. Recently, this concept has been extended to characterize wettability in non-static situations using high-resolution, two-dimensional digital images of multi-component systems. Using simple thought experiments and published experimental results, many of them decades old, it will be demonstrated that contact angles are not primary parameters – their values depend on many other parameters. Using these arguments, it will be demonstrated that contact angles are not the cause of wettability behavior but the effect of wettability behavior and other parameters. The result of this is that the contact angle cannot be used as a primary indicator of wettability except in very restricted situations. Furthermore, it will be demonstrated that even for the simple case of a capillary interface in a vertical tube, attempting to use simply a two-dimensional image to determine the contact angle can result in a wide range of measured values. This observation is consistent with some published experimental results. It follows that contact angles measured in two-dimensions cannot be trusted to provide accurate values and these values should not be used to characterize the wettability of the system.

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