Torque-coupled thermodynamic model for F_oF_1-ATPase

F_oF_1-ATPase is a motor protein complex that utilizes transmembrane ion flow to drive the synthesis of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and phosphate (Pi). While many theoretical models have been proposed to account for its rotary activity, most of them focus on the F_o or F_1 portions separately rather than the complex as a whole. Here, we propose a simple but new torque-coupled thermodynamic model of F_oF_1-ATPase. Solving this model at steady state, we find that the monotonic variation of each portion's efficiency becomes much more robust over a wide range of parameters when the F_o and F_1 portions are coupled together, as compared to cases when they are considered separately. Furthermore, the coupled model predicts the dependence of each portion's kinetic behavior on the parameters of the other. Specifically, the power and efficiency of the F_1 portion are quite sensitive to the proton gradient across the membrane, while those of the F_o portion as well as the related Michaelis constants for proton concentrations respond insensitively to concentration changes in the reactants of ATP synthesis. The physiological proton gradient across the membrane in the F_o portion is also shown to be optimal for the Michaelis constants of ADP and phosphate in the F_1 portion during ATP synthesis. Together, our coupled model is able to predict key dynamic and thermodynamic features of the F_oF_1-ATPase in vivo semiquantitatively, and suggests that such coupling approach could be further applied to other biophysical systems

Dynamic and static study of the fluid-structure interaction problem on elastic box plate

The influence of coupling to the fluid field is neglected in the classic fluid mechanics theory. United Lagrangian-Eulerian method is used to solve the fluid-structure interaction (FSI) problem of the nonviscous and incompressible fluid flow around an elastic box plate taking into account the influence of deformation of the elastic plate. In this approach, each material is described in its preferred reference frame. Fluid flows are given in Eulerian coordinates whereas the elastic body is treated in a Lagrangian framework. The coupling between the fluid and elastic body domains is kinematic and dynamic conditions at the body surface. The kinematic and dynamic conditions are given in Eulerian and Lagrangian coordinates. The dynamic equation of the elastic box plate is expressed combining the dynamic conditions at the interface. The knowledge of both dynamic and static deformations, static pressure and velocity distributions is given by using the Taylor expansions method. The effect of plate deformation is taken into account for the obtained solutions

Ionized gas outflows in infrared-bright dust-obscured galaxies selected with WISE and SDSS

We present the ionized gas properties of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme optical/IR color, $(i - [22])_{\rm AB} > 7.0$, selected with the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). For 36 IR-bright DOGs that show [OIII]$\lambda$5007 emission in the SDSS spectra, we performed a detailed spectral analysis to investigate their ionized gas properties. In particular, we measured the velocity offset (the velocity with respect to the systemic velocity measured from the stellar absorption lines) and the velocity dispersion of the [OIII] line. We found that the derived velocity offset and dispersion of most IR-bright DOGs are larger than those of Seyfert 2 galaxies (Sy2s) at $z < 0.3$, meaning that the IR-bright DOGs show relatively strong outflows compared to Sy2s. This can be explained by the difference of IR luminosity contributed from active galactic nucleus, $L_{\rm IR}$ (AGN), because we found that (i) $L_{\rm IR}$ (AGN) correlates with the velocity offset and dispersion of [OIII] and (ii) our IR-bright DOGs sample has larger $L_{\rm IR}$ (AGN) than Sy2s. Nevertheless, the fact that about 75% IR-bright DOGs have a large ($>$ 300 km s$^{-1}$) velocity dispersion, which is a larger fraction compared to other AGN populations, suggests that IR-bright DOGs are good laboratories to investigate AGN feedback. The velocity offset and dispersion of [OIII] and [NeIII]$\lambda$3869 are larger than those of [OII]$\lambda$3727, which indicates that the highly ionized gas tends to show more stronger outflows.Comment: 19 pages, 16 figures, and 2 tables, accepted for publication in Ap