Ion currents through Kir potassium channels are gated by anionic lipids

Ion currents through potassium channels are gated. Constriction of the ion conduction pathway at the inner helix bundle, the textbook ‘gate’ of Kir potassium channels, has been shown to be an ineffective permeation control, creating a rift in our understanding of how these channels are gated. Here we present the first evidence that anionic lipids act as interactive response elements sufficient to gate potassium conduction. We demonstrate the limiting barrier to K+ permeation lies within the ion conduction pathway and show that this ‘gate’ is operated by the fatty acyl tails of lipids that infiltrate the conduction pathway via fenestrations in the walls of the pore. Acyl tails occupying a surface groove extending from the cytosolic interface to the conduction pathway provide a potential means of relaying cellular signals, mediated by anionic lipid head groups bound at the canonical lipid binding site, to the internal gate.

Leakage magnetic field variation induced by inner surface grooves during loading in geomagnetic environment

The leakage magnetic field which induced by the inner surface groove during loading had been measured from the outer surface in geomagnetic environment. Compared the variation of the leakage magnetic field along the load with the location and development of the groove, it was found that two phenomena are relate to the magnetic field aberration. The relation can be described by the pink-pink value and the gradient of the magnetic field aberration. This result can be used to evaluate and monitor the inner defect by the magnetic field aberration characters.

Effect of Surface Groove Structure on the Aerodynamics of Soccer Balls

Soccer balls have undergone dramatic changes in their surface structure that can affect their aerodynamics. The properties of the soccer ball surface such as the panel shape, panel orientation, seam characteristics, and surface roughness have a significant impact on its aerodynamics and flight trajectory. In this study, we performed wind-tunnel tests to investigate how the introduction of grooves on the surface of a soccer ball affects the flight stability and aerodynamic forces on the ball. Our results show that for soccer balls without grooves, changing the panel orientation of the ball causes a significant change in the drag coefficient. Soccer balls with grooves exhibited a smaller change in air resistance (Cd) in the supercritical region (20 to 30 m/s; 3.0 × 105 ≤ Re ≤ 4.7 × 105), compared to the ungrooved ball where only the panel orientation was changed. Furthermore, at power-shot speeds (25 m/s), the grooved ball exhibited smaller variations in lift force and side force than the ungrooved ball. These results suggest that a long groove structure on the surface of the soccer ball has a significant impact on the air flow around the ball in the supercritical region, and has the effect of keeping the air flow separation line constant.

Experimental Investigations of the Surface Groove Effect in Taylor-Couette-Poiseuille Flow

In this paper, we investigate the effects of an imposed axial flow on hydrodynamic instabilities’ Couette-Taylor flow in the case where the wall of the inner cylinder of the system is grouved. Without imposed axial flow, the basic flow of a fluid between two coaxial cylinders known by Couette flow, which is characterized by several temporal and spatial symmetries. The increase in the rotation causes the breaking of these symmetries. In both cases where the surface of the inner cylinder is smooth and grooved, five different flow regimes can be determined: Taylor vortex flow (TVF), wavy vortex flow (WVF), and Modulated Wavy vortex flow (MWVF). Each time the flow passes from one hydrodynamic regime to another until it enters a state of turbulence, which is characterized by the destruction of all the symmetries that existed at the beginning. In addition, when an axial flow is imposed on a Taylor-Couette flow, new helical vortex structures are observed in both cases (with and without surface groove). The influence of surface structures (grooves) on the shear stress of the wall is discussed with and without axial base flow. A spatio-temporal description of several flow models was obtained using firstly, a visualization’s qualitative study using kalliroscope particles. Secondly, a quantitative study by polarography using simple probes have been used to characterize the impact of vortex structures on the Couette-Taylor flows without and with an axial flow on the transfer.

Structural analysis of the PATZ1 BTB domain homodimer

PATZ1 is a ubiquitously expressed transcriptional repressor belonging to the ZBTB family that is functionally expressed in T lymphocytes. PATZ1 targets the CD8 gene in lymphocyte development and interacts with the p53 protein to control genes that are important in proliferation and in the DNA-damage response. PATZ1 exerts its activity through an N-terminal BTB domain that mediates dimerization and co-repressor interactions and a C-terminal zinc-finger motif-containing domain that mediates DNA binding. Here, the crystal structures of the murine and zebrafish PATZ1 BTB domains are reported at 2.3 and 1.8 Å resolution, respectively. The structures revealed that the PATZ1 BTB domain forms a stable homodimer with a lateral surface groove, as in other ZBTB structures. Analysis of the lateral groove revealed a large acidic patch in this region, which contrasts with the previously resolved basic co-repressor binding interface of BCL6. A large 30-amino-acid glycine- and alanine-rich central loop, which is unique to mammalian PATZ1 amongst all ZBTB proteins, could not be resolved, probably owing to its flexibility. Molecular-dynamics simulations suggest a contribution of this loop to modulation of the mammalian BTB dimerization interface.

Steady performance and dynamic characteristics of a superellipse groove dry gas seal at a high-speed condition

Purpose The purpose of this paper is to enhance film stiffness and control seal leakage of conventional spiral groove dry gas seal (S-DGS) at a high-speed condition by introducing a new type superellipse surface groove. Design/methodology/approach The steady-state performance and dynamic characteristics of superellipse groove dry gas seal and S-DGS are compared numerically at a high-speed condition. The optimized superellipse grooves for maximum steady-state film stiffness and dynamic stiffness coefficient are obtained. Findings Properly designed superellipse groove dry gas seal provides remarkable larger steady-state film stiffness, dynamic stiffness coefficient and lower leakage rate at a high-speed condition compared to a typical S-DGS. The optimal values of first superellipse coefficient for maximum steady and dynamic stiffness are 1.3 and 1.4, whereas the optimal values of second superellipse coefficient for which are 1.4 and 2.0, respectively. Originality/value A new type of molded line, namely, superellipse curve, is proposed to act as the boundary lines of surface groove of dry gas seal, as an alternative of typical logarithm helix. The conclusions provide references for surface groove design with larger stiffness and lower leakage rate at a high-speed condition.

Structural Analysis of the PATZ1 BTB domain homodimer

PATZ1 is a transcriptional repressor belonging to the ZBTB family that is functionally expressed in T-lymphocytes, as well as in a ubiquitous fashion. PATZ1 targets the Cd8 gene in lymphocyte development and interacts with the p53 protein to control genes important in proliferation and DNA damage response. PATZ1 exerts its activity through an N-terminal BTB domain that mediates dimerization and co-repressor interactions and a C-terminal zinc finger motif-containing domain that mediates DNA binding. Here, the crystal structures of the murine and zebrafish PATZ1 BTB domains are reported at 2.3 and 1.8 Å resolution respectively. The structures reveal that, like other ZBTB structures, the PATZ1 BTB domain forms a stable homodimer and likely binds co-repressors through a lateral surface groove that is formed upon dimerization. Analysis of the lateral groove reveals a large acidic patch in this region which contrasts previously resolved basic co-repressor binding interfaces in other ZBTB proteins. A large 30 amino acids glycine- and alanine-rich central loop, unique to mammalian PATZ1 amongst all ZBTB proteins, could not be resolved likely due to its flexibility. Modelling of this loop indicates that it can participate in the dimerization interface of BTB monomers.SynopsisThe crystal structures of the PATZ1 BTB domain in mammals and fish are homodimers. The core dimer conformation of these BTB proteins is dynamically stable, despite the presence of highly flexible regions in the dimerization interface.