Molecular chaperones assist protein folding by facilitating their "forward" folding and preventing aggregation. However, once aggregates have formed, these chaperones cannot facilitate protein disaggregation. Bacterial ClpB and its eukaryotic homolog Hsp104 are essential proteins of the heat-shock response, which have the remarkable capacity to rescue stress-damaged proteins from an aggregated state. We have determined the structure of Thermus thermophilus ClpB (TClpB) using a combination of X-ray crystallography and cryo-electron microscopy (cryo-EM). Our single-particle reconstruction shows that TClpB forms a two-tiered hexameric ring. The ClpB/Hsp104-linker consists of an 85 A long and mobile coiled coil that is located on the outside of the hexamer. Our mutagenesis and biochemical data show that both the relative position and motion of this coiled coil are critical for chaperone function. Taken together, we propose a mechanism by which an ATP-driven conformational change is coupled to a large coiled-coil motion, which is indispensable for protein disaggregation.

Highly efficient luminescence dyes based on pyrene and anthracene derivatives (see figure) are synthesized for liquid crystal dye lasers. The threshold value of one of the pyrene derivatives is as low as 1/20 that of the commonly used DCM in cholesteric liquid crystal (CLC) distributed feedback lasers. Good optical properties such as luminous efficiency and solubility in CLCs are important factors for realizing a low threshold.

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The authors have studied low threshold lasing in dye-doped cholesteric liquid crystals (CLCs). We designed and synthesized a dye, 1,3,6,8-tetrakis(6'-hexyloxy-2-naphthyl)pyrene, which has high quantum yield Φ= 0.85. Since the transition dipole moment is perpendicular to the local director of a host CLC, laser oscillation occurs at the higher energy edge of the stop band of CLC contrary to that in conventional dyes aligning parallel to the director. We evaluated lasing characteristics and found that the pyrene-doped CLC gives laser threshold of 43 nJ/pulse, which is about one order of magnitude lower than that of conventional laser dyes.