Modeling the influence of the external electric fields on water viscosity inside carbon nanotubes.

Equilibrium molecular dynamics simulations were performed to explore the effects of external electric fields and confinement on water properties inside various carbon nanotubes (CNTs). Using different GHz electric field frequencies as well as various constant electric field strengths, the radial distribution function and density profile were investigated, by which the impact of the electric fields and confinement on the water structure are revealed. The results indicated water molecules inside the CNT form layered structures due to topological confinement applying external electric fields can disturb this ordered water molecules structure and increase the viscosity of confined water, particularly in the case of CNTs with a radius less than 13.5 Å. Conversely, for CNTs with a radius greater than13.5 Å, the viscosity decreases under the influence of external oscillating or constant electric fields. How dose the synergism of confinement and external electric fields affect the water properties inside the CNTs?

Water purification modeling by functionalized hourglass-shape multilayer nano-channel.

In this study, inspired by the overall structure and operation of the aquaporin channel, graphene-based nanochannels are proposed to be used as potential membranes for the water purification process. To this end, an hourglass-shaped channel has been designed using the three-layer porous graphene sheets and the effects of some main channel's elements, such as the channel bending angle and attached functional groups to it, on the filtration performance have been examined by using molecular dynamics simulations. We find that a suitable bending channel shape can improve the channel efficiency, i.e. both the water permeability and the ion rejection rate of the suitable bent channels were more than for the straight channels. In addition, regarding the different functionalized channels, the half-functionalized channels were more efficient than the completed functionalized ones. Furthermore, by monitoring the dynamics of water molecules as they pass through the narrowest part of the channels, it was found that water molecule rotation assists water transport.

Nano-droplet jumping due to surface wettability variation: molecular modeling approach.

The effect of substrate hydrophobicity on the dynamics of water nano-droplets is computationally studied using the molecular dynamics method. It is observed that the droplet moves upward by increasing the substrate hydrophobicity and then falls down onto the substrate, and during this process, the droplet-substrate interfacial area effectively declines. Moreover, the results indicate that above a critical substrate hydrophobicity, which depends on the droplet radius, the droplet completely detaches from the substrate. The droplet behavior is described at the molecular level using van der Waals attractions for the liquid-solid interface.

Impacts of external electric fields on the permeation of glycerol and water molecules through aquaglyceroporin-7: molecular dynamics simulation approach.

The aquaglyceroporin-7 (AQP7) protein channels facilitate the permeation of glycerol and water molecules through cell membranes by passive diffusion and play a crucial role in cell physiology. Considering the wide-spirit usage of radiofrequency electromagnetic fields in our daily life, in this study, the effects of constant and GHz electric fields were investigated on the dynamics of glycerol and water molecules inside the AQP7. To this end, four different molecular simulation groups were carried out in the absence and presence of electric fields. The results reveal that the free energy profile of the glycerol permeation inside the channel is reduced in the presence of the field of 0.2 mV/nm and the oscillating field of 10 GHz. In addition, exposing the channel to the electric field of 0.2 mV/nm assisted the water transport through the channel with no considerable effect on channel stability. These observations provide a framework for understanding how such fields could alter normal operation of protein channels, which may lead to disease beginning or being used in disease treatment. Glycerol and water molecules permeation through the aquaglyceroporin-7 channel can be influenced by application of external electric fields.

Water flow modeling through a graphene-based nanochannel: theory and simulation.

Understanding the behavior of water molecule transport through artificial nano-channels is essential in designing novel nanofluidic devices that could be used especially in nanofiltration processes. In this study, using nonequilibrium molecular dynamics (MD) simulations, we simulated the water flow through different graphene-based channels to investigate the influences of some key factors such as the channel thickness and applied pressure on the water flow. It was demonstrated that the water flow was enhanced by increasing the applied pressure and channel thickness. Our results indicated that a third order polynomial curve could describe the variation of the water flow as a function of the channel thickness and the applied pressure. In addition, we improved the hydrodynamics equation used to consider the water flow through nano-channels, by adding two terms to describe the slip effect and the entrance/exit effect, in which the first term increased the water flow rate, while the second term reduced it. This study may be helpful in designing high-performance graphene-based membranes with some practical applications such as desalination.

Multilayer Nanoporous Graphene as a Water Purification Membrane.

Porous graphene sheets can be considered as an ultrathin membrane in reverse osmosis water desalination processes. In this paper, employing the molecular dynamics simulation method, the performance of multilayer porous graphene membranes with different pore sizes, layer separation, and layer number were investigated. We found that salt rejection and water flux through the membrane significantly depend on the graphene pore size and number of graphene layers, and controlling these parameters could improve the filtration process. It was shown that our 2-layer designed graphene membranes with the pore radius of 3.3 Å and layer separation of 20 Å, can reject more than 86% of ions. Also, no filtration process had occurred for graphene layer separation less than 5 Å. The results of this study that are described by ion hydration radius and water velocity distributions can be used to improve the knowledge of water desalination at the molecular level, which leads to design more efficient multilayer graphene membranes for water purification.

Identifying binding modes of two synthetic derivatives of adrenalin to the α2C-adrenoceptor by using molecular modeling; insights into the α2C-adrenoceptor activation.

Although, α2C adrenergic receptor (AR) mediates a number of physiological functions in vivo and has great therapeutic potential, the absence of its crystal structure is a major difficulty in the activation mechanism studies and drug design endeavors. Here, a homology model of α2C AR has been presented by means of multiple sequence alignment. The used templates were the latest crystal structures of the other ARs (Protein Data Bank IDs: 2R4R, 2RH1, 4GPO, 3P0G, 4BVN and 4LDO) that have 38.4% identity with the query. We then conducted docking simulations to understand and analyze the binding of noradrenaline (NOR), and its derivatives, namely arachidonoyl adrenalin (AA-AD) and arachidonoyl noradrenalin (AA-NOR) to the receptor. The existence of H-bonds between the ligands and SER218 residue implies the same binding site of derivatives with respect to the NOR. AA-AD and AA-NOR bind to the receptor with the larger binding affinities. The presence of salt bridge between ARG149 and GLU377 in the free receptor, obtained from molecular dynamics studies proved that the receptor still is in its basal state before binding process take places. The activation process is characterized by increasing in the RMSD values of the backbone receptor in the bound state, increasing the RMSF of the transmembrane involved in the activation process and the disappearance of the ARG149-GLU377 salt bridge.