Ground-state cooling of mechanical oscillator via quadratic optomechanical coupling with two coupled optical cavities.

We present a scheme for the electromagnetically induced transparency (EIT)-like nonlinear ground-state cooling in a double-cavity optomechanical system in which an optical cavity mode is coupled parametrically to the square of the position of a mechanical oscillator, an additional auxiliary cavity is coupled to the optomechanical cavity. The optimum cooling conditions is derived, based on which the heating process can be well suppressed and the mechanical resonator can be cooled with an optimal effect to near its ground state through EIT-like cooling mechanism even in unresolved sideband regime. It is demonstrated by numerical simulations that not only the average phonon number of steady state is lower than that of single-cavity optomechanical system, but also the cooling rate is greatly faster than that of the linear optomechanical coupling due to the two-phonon cooling process in the quadratic coupling. Also, the ground-state cooling is achievable even with a relatively weak quadratic coupling strengthby tunning the coupling between two cavities to reach the optimum cooling conditions, thus provides an solution for overcoming the limitations of weak quadratic coupling rate in experiments. The proposed approach provides a platform for quantum manipulation of macroscopic mechanical devices beyond the resolved sideband limit and linear coupling regime.

The binding interface of kindlin-2 and ILK involves Asp344/Asp352/Thr356 in kindlin-2 and Arg243/Arg334 in ILK.

Focal adhesion (FA) proteins, kindlin-2 and integrin-linked kinase (ILK), regulate cell adhesion and migration. ILK interacts with and promotes kindlin-2 targeting to FAs. Leu353 and Leu357 in kindlin-2 have been reported to be important for the interaction between kindlin-2 and ILK. However, the binding interface between kindlin-2 and ILK remains unclear. Using molecular modeling and molecular dynamics simulations, we show that Asp344, Asp352, and Thr356 in kindlin-2 and Arg243 and Arg334 in ILK kinase domain (KD) are important in kindlin-2/ILK complex formation. Mutations that disrupt these interactions abrogate kindlin-2 and ILK colocalization in HeLa cells. The interactions are direct based on data from pull-down assays using purified recombinant kindlin-2 F2-pleckstrin homology and ILK KDs. These data provide additional insights into the binding interface between kindlin-2 and ILK.