6,787 research outputs found
Dynamic hydration valve controlled ion permeability and stability of NaK channel
The K^+^, Na^+^, Ca^2+^ channels are essential to neural signalling, but our current knowledge at atomic level is mainly limited to that of K^+^ channels. Unlike a K^+^ channel having four equivalent K^+^-binding sites in its selectivity filter, a NaK channel conducting both Na^+^ and K^+^ ions has a vestibule in the middle part of its selectivity filter, in which ions can diffuse but not bind specifically. However, how the NaK channel conducts ions remains elusive. Here we find four water grottos connecting with the vestibule of the NaK selectivity filter. Molecular dynamics and free energy calculations show that water molecules moving in the vestibule-grotto complex hydrate and stabilize ions in the filter and serve as a valve in conveying ions through the vestibule for controllable ion permeating. During ion conducting, the water molecules are confined within the valve to guarantee structure stability. The efficient exquisite hydration valve should exist and play similar roles in the large family of cyclic nucleotide-gated channels which have similar selectivity filter sequences. The exquisite hydration valve mechanism may shed new light on the importance of water in neural signalling
Entanglement entropy in a holographic p-wave superconductor model
In a recent paper, arXiv:1309.4877, a holographic p-wave model has been
proposed in an Einstein-Maxwell-complex vector field theory with a negative
cosmological constant. The model exhibits rich phase structure depending on the
mass and the charge of the vector field. We investigate the behavior of the
entanglement entropy of dual field theory in this model. When the above two
model parameters change, we observe the second order, first order and zeroth
order phase transitions from the behavior of the entanglement entropy at some
intermediate temperatures. These imply that the entanglement entropy can
indicate not only the occurrence of the phase transition, but also the order of
the phase transition. The entanglement entropy is indeed a good probe to phase
transition. Furthermore, the "retrograde condensation" which is a sub-dominated
phase is also reflected on the entanglement entropy.Comment: figures added; accepted by Nuclear Physics
Nanoparticle enhanced evaporation of liquids: A case study of silicone oil and water
Evaporation is a fundamental physical phenomenon, of which many challenging
questions remain unanswered. Enhanced evaporation of liquids in some occasions
is of enormous practical significance. Here we report the enhanced evaporation
of the nearly permanently stable silicone oil by dispersing with nanopariticles
including CaTiO3, anatase and rutile TiO2. The results can inspire the research
of atomistic mechanism for nanoparticle enhanced evaporation and exploration of
evaporation control techniques for treatment of oil pollution and restoration
of dirty water
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