We investigate isothermal diffusion and growth of micron-scale liquid domains within membranes of free-floating giant unilamellar vesicles with diameters between 80 and 250 μm. Domains appear after a rapid temperature quench, when the membrane is cooled through a miscibility phase transition such that coexisting liquid phases form. In membranes quenched far from a miscibility critical point, circular domains nucleate and then progress within seconds to late stage coarsening in which domains grow via two mechanisms 1), collision and coalescence of liquid domains, and 2), Ostwald ripening. Both mechanisms are expected to yield the same growth exponent, α = 1/3, where domain radius grows as time(α). We measure α = 0.28 ± 0.05, in excellent agreement. In membranes close to a miscibility critical point, the two liquid phases in the membrane are bicontinuous. A quench near the critical composition results in rapid changes in morphology of elongated domains. In this case, we measure α = 0.50 ± 0.16, consistent with theory and simulation.

the phase diagram itself. Brewster angle microscopy allows one to image the domains in a Langmuir monolayer with and without the probe molecules to directly test their effect. The combined Brewster angle (BAM)/ fluorescence microscope allows us to image simultaneously with the two techniques exactly the same domains in the Langmuir film. In general, the images taken by the two microscopes compare well. Comparison of the techniques can then make it easier to correlate the different domain properties leading to contrast in the two techniques. Some types of domains may however be much more evident with BAM than with FM. When placed in water, lipid molecules form multilamellar vesicles (MLVs) in which lipid layers are separated by water regions. These interlamellar water regions have thicknesses on the order of 1 to 10 nanometers depending on lipid type. What happens if water contains buffer molecules? Will buffer molecules be taken inside the MLVs? If yes, then to what extent? These questions arise because the physical properties of water regions next to lipid membranes have been shown to differ from bulk water [1]. We would like to know how buffer molecules and other solutes partition between MLVs and the outer solution. To determine this partitioning, we use lipid membranes that sink in pure water but float in buffer solutions of certain concentrations. We then find the exact concentration for which the mass density of the solution matches that of the MLVs. This density matching allows us to calculate the ratio between water and buffer molecules present inside MLVs by using data from smallangle x-ray scattering. For KCl solutions, as well as for solutions of common buffers, we find that solutes are excluded from the interlamellar water regions creating a solute deficit inside the MLVs. [1] Petrache et al., Biophys.

Cholesterol is crucial to the mechanical properties of cell membranes that are important to cells’ behavior. Its depletion from the cell membranes could be dramatic. Among cyclodextrins (CDs), methyl beta cyclodextrin (MβCD) is the most efficient to deplete cholesterol (Chol) from biomembranes. Here, we focus on the depletion of cholesterol from a C16 ceramide/cholesterol (C16-Cer/Chol) mixed monolayer using MβCD. While the removal of cholesterol by MβCD depends on the cholesterol concentration in most mixed lipid monolayers, it does not depend very much on the concentration of cholesterol in C16-Cer/Chol monolayers. The surface pressure decay during depletion were described by a stretched exponential that suggested that the cholesterol molecules are unable to diffuse laterally and behave like static traps for the MβCD molecules. Cholesterol depletion causes morphology changes of domains but these disrupted monolayers domains seem to reform even when cholesterol level was low.

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The domain of graphene's application is highly multifaceted in the recent years but developing quintessential quality of graphene is quite challenging for industrial sectors via facile route. In this article, an indigenous one step production of graphene from graphite powder by mere stirring and using eco‐friendly aqueous solvent is reported. This fabrication process also bypass the conventional multistep involved previously. The role of sodium dodecyl sulfate (SDS) as a surfactant and the effect of stirring at different time intervals are studied, which clearly indicates that the surfactant facilitates the dispersion of the precursor in water at room temperature and the prolonged stirring helps to break the labile van der Waals forces within the graphitic structure.

When compressed in the intermediate temperature range below the chain-melting transition yet in the low-pressure liquid phase, Langmuir monolayers made of chiral lipid molecules form hierarchical structures. Using Brewster angle microscopy to reveal this structure, we found that as the liquid monolayer is compressed, an optically anisotropic condensed phase nucleates in the form of long, thin claws. These claws pack closely to form stripes. This appears to be a new mechanism for forming stripes in Langmuir monolayers. In the lower temperature range, these stripes arrange into spirals within overall circular domains, while near the chain-melting transition, the stripes arrange into target patterns.We attributed this transition to a change in boundary conditions at the core of the largest-scale circular domains.

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Low temperature heating creates scintillating opportunity in controlling the reaction condition and designing the suitable nitrogen containing graphene oxide (NGO) for material researchers and industrial applications. Herein, one step synthesis of NGO from low temperature heating (≈ 120–125 °C) is reported from a nongraphitic nitrogenous precursor in contrast to the conventional methods using graphitic precursors, oxidizers, and N‐containing dopants. The formation of nanosheets of NGO with high nitrogen content (≈19%) is achieved from 3‐aminophenol in presence of trace amount of air bypassing doping and oxidizing agents. The presence of –NH2 and –OH in the precursor plays a vital role in the condensation and aromatization. The chemistry of formation of NGO is studied and the mechanism confirms the presence of pyridinic‐N, graphitic‐N, and pyrrolic‐N in the nanosheets. Further urea is used to reduce NGO into reduced nitrogen graphene oxide, retaining the sheet structure.