The Far-Infrared Surveyor (FIS) is one of two focal plane instruments on the AKARI satellite. FIS has four photometric bands at 65, 90, 140, and 160 µm, and uses two kinds of array detectors. The FIS arrays and optics are designed to sweep the sky with high spatial resolution and redundancy. The actual scan width is more than eight arcmin, and the pixel pitch is matches the diffraction limit of the telescope. Derived point spread functions (PSFs) from observations of asteroids are similar to the optical model. Significant excesses, however, are clearly seen around tails of the PSFs, whose contributions are about 30% of the total power. All FIS functions are operating well in orbit, and its performance meets the laboratory characterizations, except for the two longer wavelength bands, which are not performing as well as characterized. Furthermore, the FIS has a spectroscopic capability using a Fourier transform spectrometer (FTS). Because the FTS takes advantage of the optics and detectors of the photometer, it can simultaneously make a spectral map. This paper summarizes the in-flight technical and operational performance of the FIS.
In two-dimensional interfacial assemblies, there is an interplay between molecular ordering and interface geometry, which determines the final morphology and order of entire systems. Here we present the interfacial phenomenon of spontaneous facet formation in a water droplet driven by designed peptide assembly. The identified peptides can flatten the rounded top of a hemispherical droplet into a plane by forming a macroscopic two-dimensional crystal structure. Such ordering is driven by the folding geometry of the peptide, interactions of tyrosine and crosslinked stabilization by cysteine. We discover the key sequence motifs and folding structures and study their sequence-specific assembly. The well-ordered, densely packed, redox-active tyrosine units in the YYACAYY (H-Tyr-Tyr-Ala-Cys-Ala-Tyr-Tyr-OH) film can trigger or enhance chemical/electrochemical reactions, and can potentially serve as a platform to fabricate a molecularly tunable, self-repairable, flat peptide or hybrid film.
The oxygen evolution reaction (OER) is considered a major bottleneck in the overall water electrolysis process. In this work, highly active manganese oxide nano-catalysts were synthesized via hot injection. Facile surface treatment generated Mn(III) species on monodisperse 10 nm MnO nanocrystals (NCs). Size dependency of MnO NCs on OER activity was also investigated. Surprisingly, the partially oxidized MnO NCs only required 530 mV @ 5 mA cm−2 under near neutral conditions.
Piscidin 1 (Pis-1) is a novel cytotoxic peptide with a cationic alpha-helical structure isolated from the mast cells of hybrid striped bass. In our previous study, we showed that Pis-1[PG] with a substitution of Pro(8) for Gly(8) in Pis-1 had higher bacterial cell selectivity than Pis-1. We designed peptoid residue-substituted peptide, Pis-1[NkG], in which Gly(8) of Pis-1 was replaced with Nlys (Lys peptoid residue). Pis-1[NkG] had higher antibacterial activity and lower cytotoxicity against mammalian cells than Pis-1 and Pis-1[PG]. We determined the tertiary structure of Pis-1[PG] and Pis-1[NkG] in the presence of DPC micelles by NMR spectroscopy. Both peptides had a three-turn helix in the C-terminal region and a bent structure in the center. Pis-1[PG] has a rigid bent structure at Pro(8) whereas Pis-1[NkG] existed as a dynamic equilibrium of two conformers with a flexible hinge structure at Nlys(8). Depolarization of the membrane potential of Staphylococcus aureus and confocal laser-scanning microscopy study revealed that Pis-1[NkG] effectively penetrated the bacterial cell membrane and accumulated in the cytoplasm, whereas Pis-1[PG] did not penetrate the membrane but remained outside or on the cell surface. Introduction of a lysine peptoid at position 8 of Pis-1 provided conformational flexibility and increased the positive charge at the hinge region; both factors facilitated penetration of the bacterial cell membrane and conferred bacterial cell selectivity on Pis-1[NkG].
In the investigation of a chemical reaction, researchers typically survey variables such as time, temperature, and stoichiometry to optimize yields. This Account demonstrates how control of these variables, often in nontraditional ways, can provide significant improvements in enantiomeric ratios for asymmetric reactions. Dynamic thermodynamic resolution (DTR) offers a convenient method for the resolution of enantiomeric products in the course of a reaction. This process depends on an essential requirement: the equilibration of the penultimate diastereomers must be subject to external control. As a general case, the reaction of A(R), A(S) with B under the influence of the chiral species, L*, gives resolved products C(R) and C(S). In the first step of dynamic resolution under thermodynamic control, the enantiomeric reactants A(R) and A(S) and L* form the diastereomers A(R)/L* and A(S)/L*. The equilibrium between A(R) and A(S) can be rapid, slow, or not operative, and L* can represent a ligand, an auxiliary, or a crystallization process that provides a chiral environment. Second, the populations of the diastereomers are controlled, usually by thermal equilibration. Finally, the reaction of the diastereomers with a reagent B provides the enantiomeric products C(R) and C(S). The control of the diastereomeric equilibrium distinguishes DTR from other resolution techniques. By contrast, physical resolutions separate thermodynamically stable, nonequilibrating diastereomers, and dynamic kinetic resolutions utilize kinetic control for reactions of rapidly equilibrating diastereomers. The dynamic thermodynamic resolutions discussed in this Account illustrate cases of significantly improved enantioselectivities using this technique. Although many of the well-recognized cases come from organolithium chemistry, the principles are general, and we also present cases facilitated by other chemistries. This approach has been used to control enantioselectivities in a number of different reactions, with improvements in enantiomeric ratios up to 99% from essentially racemic reactants.
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