Mapping bilayer thickness in the ER membrane

In the plasma membrane and in synthetic membranes, resident lipids may laterally unmix to form domains of distinct biophysical properties. Whether lipids also drive the lateral organization of intracellular membranes is largely unknown. Here, we describe genetically encoded fluorescent reporters visualizing local variations in bilayer thickness. Using them, we demonstrate that long-chained ceramides promote the formation of discrete domains of increased bilayer thickness in the yeast ER, particularly in the future plane of cleavage and at ER–trans-Golgi contact sites. Thickening of the ER membrane in the cleavage plane contributed to the formation of lateral diffusion barriers, which restricted the passage of short, but not long, protein transmembrane domains between the mother and bud ER compartments. Together, our data establish that the ER membrane is laterally organized and that ceramides drive this process, and provide insights into the physical nature and biophysical mechanisms of the lateral diffusion barriers that compartmentalize the ER.

How Thermal Aging Affects Ignition and Combustion Properties of Reactive Al/CuO Nanolaminates: A Joint Theoretical/Experimental Study

The paper reports a joint experimental/theoretical study on the aging of reactive Al/CuO nanolaminates, investigating both structural modifications and combustion properties of aged systems. We first show theoretically that the long-term storage (over several decades) in ambient temperature marginally affects nanolaminates structural properties with an increase in an interfacial layer of only 0.3 nm after 30 years. Then, we observe that the first thermal aging step occurs after 14 days at 200 °C, which corresponds to the replacement of the natural Al/CuO interfaces by a proper ~11 nm thick amorphous alumina. We show that this aging step does impact the nanolaminates structure, leading, for thin bilayer thicknesses, to a substantial loss of the energetic reservoir: considering a stoichiometric Al/CuO stack, the heat of reaction can be reduced by 6–40% depending on the bilayer thickness ranging from 150 nm (40%) to 1 µm (6%). The impact of such thermal aging (14 days at 200 °C) and interfacial modification on the initiation and combustion properties have been evaluated experimentally and theoretically. Varying Al to CuO ratio of nanolaminates from 1 to 3, we show that ignition time of aged systems does not increase over 10% at initiation power densities superior to 15 W·mm−2. In contrast, burn rate can be greatly impacted depending on the bilayer thickness: annealing a stoichiometric nanolaminates with a bilayer thickness of 300 nm at 200 °C for 14 days lowers its burn rate by ~25%, whereas annealing a fuel rich nanolaminates with the same bilayer thickness under the same thermal conditions leads to a burn rate decrease of 20%. When bilayer thickness is greater than 500 nm, the burn rate is not really affected by the thermal aging. Finally, this paper also proposes a time–temperature diagram to perform accelerated thermal aging.

Facile Mixing of Phospholipids Promotes Self-Assembly of Low-Molecular-Weight Biodegradable Block Co-Polymers into Functional Vesicular Architectures

In this work, we have used low-molecular-weight (PEG12-b-PCL6, PEG12-b-PCL9 or PEG16-b-PLA38; MW, 1.25–3.45 kDa) biodegradable block co-polymers to construct nano- and micron-scaled hybrid (polymer/lipid) vesicles, by solvent dispersion and electroformation methods, respectively. The hybrid vesicles exhibit physical properties (size, bilayer thickness and small molecule encapsulation) of a vesicular boundary, confirmed by cryogenic transmission electron microscopy, calcein leakage assay and dynamic light scattering. Importantly, we find that these low MW polymers, on their own, do not self-assemble into polymersomes at nano and micron scales. Using giant unilamellar vesicles (GUVs) model, their surface topographies are homogeneous, independent of cholesterol, suggesting more energetically favorable mixing of lipid and polymer. Despite this mixed topography with a bilayer thickness similar to that of a lipid bilayer, variation in surface topology is demonstrated using the interfacial sensitive phospholipase A2 (sPLA2). The biodegradable hybrid vesicles are less sensitive to the phospholipase digestion, reminiscent of PEGylated vesicles, and the degree of sensitivity is polymer-dependent, implying that the nano-scale surface topology can further be tuned by its chemical composition. Our results reveal and emphasize the role of phospholipids in promoting low MW polymers for spontaneous vesicular self-assembly, generating a functional hybrid lipid-polymer interface.

Electrochemical Corrosion Behavior of TiAlN/CrN Nanoscale Multilayer Coatings by Multi-Arc Ion Plating in 3.5% NaCl Solution

Multi-arc ion plating was used to deposit TiAlN/CrN multilayer coatings with different bilayer thicknesses on Type 316L stainless steel. The impacts of the bilayer thickness on the electrochemical performance of the TiAlN/CrN multilayer coatings were explored in a neutral saline (3.5% NaCl) solution. The fracture cross-sectional morphology of the as-deposited coatings were investigated by scanning electron microscope. The crystal structure and preferred orientation were analyzed by x-ray diffraction. The interface characteristic was detected by transmission electron microscopy. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used for as-deposited coatings. Corroded surface morphology and EIS of the 15-day immersion coatings and substrate were examined to analyze the anticorrosion performance. EIS showed an increase of polarization resistance (Rp) and a decrease in constant-phase element (CPE) for multilayer coatings with a decrease in bilayer thickness. After 15 days of immersion, the EIS plot showed that the C3 coating (with 20 bilayers) had the lowest electrical double-layer capacitance (CPEdl) and highest charge transfer resistance (Rct) in all samples. The relative decay of the Rp of the C3 coating was the smallest compared with the as-deposited coatings, which shows a satisfactory corrosion resistance. The electrochemical tests and immersion corrosion morphology showed that the existence of a large number of interfaces between individual layers in a multilayer structure inhibits the pitting propagation significantly and enhances the corrosion resistance.

Characterization of ultrasonic soldering of Ti and Ni with Ni/Al reactive multilayer deposition

The joining of Ti and Ni at low temperatures was analysed in this work. For joining pure Ti and Ni coins of 1.5 mm in thickness were used. Reactive multilayer thin films/foils with nanometric period (bilayer thickness), in particular Ni/Al multilayers, have been used to promote joining in two thickness of 28 and 55 nm. The ultrasonic soldering with SnAgTi active solder has been used for “hard-to-solder” material. The structural evaluation of soldered joint was studied by optical microscopy and EDX analysis. The structural analysis was focused to the creation of intermetallic layers in the joint interface. The mechanical properties of solder joints were tested by shear strength.