Simultaneous control of haze and transmittance using a dye-doped cholesteric liquid crystal cell

We propose a light shutter device using dye-doped cholesteric liquid crystals for a high-visibility see-through display. In the focal-conic state, the proposed device can perfectly block the background image through simultaneous use of light scattering and absorption effects in a single-layered structure. By switching the proposed device placed at the backside of a see-through display, we can choose transparent or high-visibility display modes in a see-through display.     

Transition metal ion directed supramolecular assembly of one- and two-dimensional polyrotaxanes incorporating cucurbituril

This paper reports a synthetic strategy to construct one- and two-dimensional (1D and 2D) polyrotaxanes, in which a number of rings are threaded onto a coordination polymer, by the combination of self-assembly and coordination chemistry. Our approach to construct polyrotaxanes with high structural regularity involves threading a cucurbituril (CB) "bead" with a short "string" to form a stable pseudorotaxane, followed by linking the pseudorotaxanes with metal ions as "linkers" to organize into a 1D or 2D polyrotaxane. A 4- or 3-pyridylmethyl group is attached to each end of 1,4-diaminobutane or 1,5-diaminopentane to produce the short "strings", which then react with the cucurbituril "bead" to form stable pseudorotaxanes. The reaction of the pseudorotaxanes with various transition metal ions including CuII, CoII, NiII, AgI, and CdII produces 1D or 2D polyrotaxanes, in which many molecular "beads" are threaded onto 1D or 2D coordination polymers as confirmed by X-ray crystallography. The overall structure of a polyrotaxane is the result of interplay among various factors that include the coordination preferences of the metal ion, spatial disposition of the donor atoms with respect to the CB beads in the pseudorotaxane, and the size and coordination ability of the counteranion.     

Single-stage anaerobic codigestion for mixture wastes of simulated Korean food waste and waste activated sludge

Korean food waste was treated with a single-stage anaerobic codigester (SSAD) using waste activated sludge (WAS) generated from a municipal wastewater treatment plant. The stability and performance of the system was analyzed. The C/N ratio was improved with increasing food waste fraction of feed mixture. The pH, alkalinity, and free ammonia nitrogen concentration were the parameters used to evaluate the digester’s stability. The experimentally determined values of the parameters indicated that there were no methane inhibitions in the digester. Digester performance was determined by measuring the total chemical oxygen demand TCOD), volate solids (VS) removal, methane content in biogas, methane production rate (MPR), and specific methane productivity. Methane content in biogas and MPR were significantly dependent on hydraulic retention time (HRT) and ratio of food waste to WAS. The methane content in biogas decreased at shorter HRT or higher organic loading rate (OLR) with increased food waste fraction. Concerning the performance of the codigester, the optimum operating condition of the SSAD was found to be at an HRT of 10 d with a feed mixture ratio of 50% food waste and 50% WAS. A TCOD removal efficiency of 53.6% and a VS removal efficiency of 53.7% were obtained at an OLR of 5.96 kg of TCOD/(m³·d) and 3.14 kg of VS/(m³·d), respectively. A maximum MPR of 1.15 m³ CH₄/(m³·d) and an SMP of 0.37 m³ CH₄/kg of VS_feed were obtained at an HRT of 10 d with a methane content of 63%.     

Targeted Degradation of Transcription Coactivator SRC-1 through the N-Degron Pathway

Aberrantly elevated steroid receptor coactivator-1 (SRC-1) expression and activity are strongly correlated with cancer progression and metastasis. Here we report, for the first time, the development of a proteolysis targeting chimera (PROTAC) that is composed of a selective SRC-1 binder linked to a specific ligand for UBR box, a unique class of E3 ligases recognizing N-degrons. We showed that the bifunctional molecule efficiently and selectively induced the degradation of SRC-1 in cells through the N-degron pathway. Importantly, given the ubiquitous expression of the UBR protein in most cells, PROTACs targeting the UBR box could degrade a protein of interest regardless of cell types. We also showed that the SRC-1 degrader significantly suppressed cancer cell invasion and migration in vitro and in vivo. Together, these results demonstrate that the SRC-1 degrader can be an invaluable chemical tool in the studies of SRC-1 functions. Moreover, our findings suggest PROTACs based on the N-degron pathway as a widely useful strategy to degrade disease-relevant proteins.     

Visible‐Light‐Induced ortho‐Selective Migration on Pyridyl Ring: Trifluoromethylative Pyridylation of Unactivated Alkenes

The photocatalyzed ortho‐selective migration on a pyridyl ring has been achieved for the site‐selective trifluoromethylative pyridylation of unactivated alkenes. The overall process is initiated by the selective addition of a CF₃ radical to the alkene to provide a nucleophilic alkyl radical intermediate, which enables an intramolecular endo addition exclusively to the ortho‐position of the pyridinium salt. Both secondary and tertiary alkyl radicals are well‐suited for addition to the C2‐position of pyridinium salts to ultimately provide synthetically valuable C2‐fluoroalkyl functionalized pyridines. Moreover, the method was successfully applied to the reaction with P‐centered radicals. The utility of this transformation was further demonstrated by the late‐stage functionalization of complex bioactive molecules.     

A highly regioselective synthesis of 2-aryl-6-chlorobenzothiazoles employing microwave-promoted Suzuki-Miyaura coupling reaction

Suzuki-Miyaura coupling reactions of 2,6-dichlorobenzothiazole with arylboronic acids, promoted by microwave heating, efficiently produce 2-aryl-6-chlorobenzothiazoles in a highly regioselective manner. This process serves as the foundation for a simple method to rapidly construct 2-aryl-6-chlorobenzothiazole libraries.     

The role of sample collection method and the bias between different standard matrices in the determination of volatile organic compounds in air

This study was undertaken to assess the relative bias between two types of sampling methods for volatile organic compounds (VOCs), i.e., sorbent tube vs. bag sampling methods and between different standard phases. For the purpose of this comparative study, gaseous standards containing three major aromatic VOCs (benzene, toluene, and xylene—commonly called BTX) were analyzed by thermo-desorption gas chromatography (TD-GC) with flame ionization detector. According to our findings, the relative response of target compounds can be smaller in the bag method than in the tube method. Although the relative bias varies with the sample transfer conditions for the TD, the mean slope values of the former are smaller by up to 20% relative to the latter, possibly due to sorptive loss on the bag sampler. In addition, the effects of different standard matrices (i.e. liquid and gas phases) were also examined using the sorbent tube method. The results indicated that the slope values of the gas-phase standard were smaller by half (about 43–56%) than the liquid-phase standard. Consequently, information concerning the extent of relative bias between sampling methods (e.g., bag and tube) or standard matrices (e.g., gas and liquid) should be considered as one of the key factors in TD applications.     

Expression of Codon-Optmized Phosphoenolpyruvate Carboxylase Gene from Glaciecola sp. HTCC2999 in Escherichia coli and its Application for C4 Chemical Production

We examined the expression of the phosphoenolpyruvate carboxylase (PEPC) gene from marine bacteria in Escherichia coli using codon optimization. The codon-optimized PEPC gene was expressed in the E. coli K-12 strain W3110. SDS-PAGE analysis revealed that the codon-optimized PEPC gene was only expressed in E. coli, and measurement of enzyme activity indicated the highest PEPC activity in the E. coli SGJS112 strain that contained the codon-optimized PEPC gene. In fermentation assays, the E. coli SGJS112 produced the highest yield of oxaloacetate using glucose as the source and produced a 20-times increase in the yield of malate compared to the control. We concluded that the codon optimization enabled E. coli to express the PEPC gene derived from the Glaciecola sp. HTCC2999. Also, the expressed protein exhibited an enzymatic activity similar to that of E. coli PEPC and increased the yield of oxaloacetate and malate in an E. coli system.     

Motions on the millisecond time scale and multiple conformations of HIV-1 capsid protein: implications for structural polymorphism of CA assemblies

The capsid protein (CA) of human immunodeficiency virus 1 (HIV-1) assembles into a cone-like structure that encloses the viral RNA genome. Interestingly, significant heterogeneity in shape and organization of capsids can be observed in mature HIV-1 virions. In vitro, CA also exhibits structural polymorphism and can assemble into various morphologies, such as cones, tubes, and spheres. Many intermolecular contacts that are critical for CA assembly are formed by its C-terminal domain (CTD), a dimerization domain, which was found to adopt different orientations in several X-ray and NMR structures of the CTD dimer and full-length CA proteins. Tyr145 (Y145), residue two in our CTD construct used for NMR structure determination, but not present in the crystallographic constructs, was found to be crucial for infectivity and engaged in numerous interactions at the CTD dimer interface. Here we investigate the origin of CA structural plasticity using solid-state NMR and solution NMR spectroscopy. In the solid state, the hinge region connecting the NTD and CTD is flexible on the millisecond time scale, as evidenced by the backbone motions of Y145 in CA conical assemblies and in two CTD constructs (137-231 and 142-231), allowing the protein to access multiple conformations essential for pleimorphic capsid assemblies. In solution, the CTD dimer exists as two major conformers, whose relative populations differ for the different CTD constructs. In the longer CTD (144-231) construct that contains the hinge region between the NTD and CTD, the populations of the two conformers are likely determined by the protonation state of the E175 side chain that is located at the dimer interface and within hydrogen-bonding distance of the W184 side chain on the other monomer. At pH 6.5, the major conformer exhibits the same dimer interface as full-length CA. In the short CTD (150-231) construct, no pH-dependent conformational shift is observed. These findings suggest that the presence of structural plasticity at the CTD dimer interface permits pleiotropic HIV-1 capsid assembly, resulting in varied capsid morphologies.     

Hydrated alizarin complexes: hydrogen bonding and proton transfer

We investigated the hydrogen bonding structures and proton transfer for the hydration complexes of alizarin (Az) produced in a supersonic jet using fluorescence excitation (FE), dispersed laser induced fluorescence (LIF), visible-visible hole burning (HB), and fluorescence detected infrared (FDIR) spectroscopy. The FDIR spectrum of bare Az with two O-H groups exhibits two vibrational bands at 3092 and 3579 cm(-1), which, respectively, correspond to the stretching vibration of O1-H1 that forms a strong intramolecular hydrogen bond with the C9=O9 carbonyl group and the stretching vibration of O2-H2 that is weakly hydrogen-bonded to O1-H1. For the 1:1 hydration complex Az(H(2)O)(1), we identified three conformers. In the most stable conformer, the water molecule forms hydrogen bonds with the O1-H1 and O2-H2 groups of Az as a proton donor and proton acceptor, respectively. In the other conformers, the water binds to the C10=O10 group in two nearly isoenergetic configurations. In contrast to the sharp vibronic peaks in the FE spectra of Az and Az(H(2)O)(1), only broad, structureless absorption was observed for Az(H(2)O)(n) (n≥ 2), indicating a facile decay process, possibly due to proton transfer in the electronic excited state. The FDIR spectrum with the wavelength of the probe laser fixed at the broad band exhibited a broad vibrational band near the O2-H2 stretching vibration frequency of the most stable conformer of Az(H(2)O)(1). With the help of theoretical calculations, we suggest that the broad vibrational band may represent the occurrence of proton transfer by tunnelling in the electronic ground state of Az(H(2)O)(n) (n≥ 2) upon excitation of the O2-H2 vibration.