Using systematic numerical simulations, we study the self-assembly of elongated curved nanoparticles on lipid vesicles. Our simulations are based on molecular dynamics of a coarse-grained implicit-solvent model of self-assembled lipid membranes with a Langevin thermostat. Here we consider only the case wherein the nanoparticle-nanoparticle interaction is repulsive, only the concave surface of the nanoparticle interacts attractively with the lipid head groups and only the outer surface of the vesicle is exposed to the nanoparticles. Upon their adhesion on the vesicle, the curved nanoparticles generate local curvature on the membrane. The resulting nanoparticle-generated membrane curvature leads in turn to nanoparticle self-assembly into two main types of aggregates corresponding to chain aggregates at low adhesion strengths and aster aggregates at high adhesion strength. The chain-like aggregates are due to the fact that at low values of adhesion strength, the nanoparticles prefer to lie parallel to each other. As the adhesion strength is increased, a splay angle between the nanoparticles is induced with a magnitude that increases with increasing adhesion strength. The origin of the splay angles between the nanoparticles is shown to be saddle-like membrane deformations induced by a tilt of the lipids around the nanoparticles. This phenomenon of membrane mediated self-assembly of anisotropically curved nanoparticles is explored for systems with varying nanoparticle number densities, adhesion strength, and nanoparticle intrinsic curvature.

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Static and MAS*) 35CI NMR data of CIO−4 ions in the low‐, intermediate‐ and high‐temperature phases of trimethylammonium, dimethylammonium and monomethylammonium perchlorates are reported. The observed solid‐solid phase transitions are interrelated with the motional state of the perchlorate ions. In the low‐temperature phase III of trimethylammonium perchlorate there is an anisotropic motion of the ClO−4 ions with a constant quadrupole frequency of 185 kHz and an increasing value of the asymmetry parameter when approaching phase transition III‐II. The activation energy for this motion is found to be 44.3 kj/mol. At the transition III‐II the ClO−4 ions gain orientational degrees of freedom manifested by the change of the quadrupole frequency to 159 kHz. In phase II the perchlorate ions undergo an axial motion overcoming the energy barrier of 40.7 kj/mol. In the low‐temperature phase III of dimethylammonium perchlorate there are rigid ClO−4 ions. At the phase transition III‐II the ClO−4 ions gain considerable motional freedom indicated by lowering the quadrupole frequency to 119 kHz, due to an anisotropic motion. In the high‐temperature phase I the anions undergo isotropic motion with the activation energy of 11.9 kj/mol. The low‐temperature phase III of monomethylammonium perchlorate is characterized by rigid ClO−4 ions. At the transition III‐II the ClO−4 ions gain a considerable motional freedom and undergo an axial motion in phase II. In phase I motion of the anions is isotropic. The motional behaviour of the anions along with NMR data for the cations suggests that the low‐temperature ordering of the ions in phase HI is due to hydrogen‐bonds NH … OCl, the partial breaking of which, accompanied by the phase transition III‐II, leads to an axial motion of the ions in phase II. A complete breaking of all hydrogen‐bonds in phase I allows the ions to reorient isotropically. The quadrupole coupling constant of rigid ClO−4 ions amounts to about 1 MHz.

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Using molecular dynamics simulations of a coarse-grained implicit solvent model, we investigate the binding of crescent-shaped nanoparticles (NPs) on tubular lipid membranes. The NPs adhere to the membrane through their...

The binding of crescent-shaped nanoparticles (CNPs) on nanoscale tubular membranes is investigated through systematic coarse-grained molecular dynamics simulations of an implicit-solvent model. The CNPs adhere through their concave side to the outer surface of the tubular membrane. The binding/unbinding transitions are found to be irreversible, with the threshold binding energy, E b , being higher than that of the unbinding threshold, E u . Furthermore, the difference E b -E u increases with increasing either the CNP's arclength, L np , or curvature mismatch, m=R t /R np , where R np is the CNP's radius of curvature and R t is the tube's radius. We also investigated the arrangement of a CNP on the tube and found that for m smaller than a L np -dependent m*, the CNP lies perpendicularly to the tubule. However, for m1 (or m

Nanoparticle (NP) based technologies, which are becoming increasingly prevalent component in industrial development, have many important potential medical applications including diagnosis, imaging, drug delivery, hypothermia, and photothermal therapy. Since the plasma membrane is the point of entry of cells, biomedical applications of NPs require understanding of their interactions with lipid membranes (LMs). Mixing NPs with soft materials, such as polymers and liquid crystals, often leads to cooperative behavior of NPs manifested in their self-assembly. Recent experiments have shown that the adhesion of NPs onto LMs leads to their aggregation. In order to understand this cooperative behavior, we conducted large scale and systematic molecular dynamics simulations of spherical NPs self-assembly mediated by their adhesion onto LMs using a coarse-grained implicit solvent model. In addition to the linear chains and tubes, indicated earlier by other researchers using dynamic triangulation Monte Carlo method, we observed additional novel self-assemblies corresponding to bitubes and rings. The phase diagram of the system is determined as a function of NPs size, adhesion strength, and number density on the LM. The stability of these self-assemblies, particularly bitubes and rings, was investigated using simulated annealing as well as free energy calculations.