Role of the C-terminal region of mouse inducible Hsp72 in the recognition of peptide substrate for chaperone activity

AbstractHere, we produced the C-terminal truncation variants of mouse inducible heat shock protein 72 (Hsp72) to elucidate the regulatory role of the C-terminal helical lid of Hsp70 for substrate recognition. All of the truncation variants containing the substrate binding domain bound a short-length peptide substrate CLLLSAPRR. When a large mass reduced carboxymethyl α-lactalbumin (RCMLA) as a substrate was used in gel filtration experiment, we observed the complex formation only for the truncation variants containing the long α-helix C in the helical lid. However, RCMLA binding occurred even for the variants lacking α-helix C when their C-terminal region was anchored onto a solid phase. Together with the finding that helix C is involved in the self-association of Hsp70, our present data suggest that the C-terminal region of Hsp70 modulates the substrate recognition and its kinetics may be substrate-mass dependent

Facile synthesis of picenes incorporating imide moieties at both edges of the molecule and their application to n-channel field-effect transistors

Picene derivatives incorporating imide moieties along the long-axis direction of the picene core (Cn-PicDIs) were conveniently synthesized through a four-step synthesis. Photochemical cyclization of dinaphthylethenes was used as the key step for constructing the picene skeleton. Field-effect transistor (FET) devices of Cn-PicDIs were fabricated by using ZrO2 as a gate substrate and their FET characteristics were investigated. The FET devices showed normally-off n-channel operation; the averaged electron mobility (μ) was evaluated to be 2(1) × 10−4, 1.0(6) × 10−1 and 1.4(3) × 10−2 cm2 V−1 s−1 for C4-PicDI, C8-PicDI and C12-PicDI, respectively. The maximum μ value as high as 2.0 × 10−1 cm2 V−1 s−1 was observed for C8-PicDI. The electronic spectra of Cn-PicDIs in solution showed the same profiles irrespective of the alkyl chain lengths. In contrast, in thin films, the UV absorption and photoelectron yield spectroscopy (PYS) indicated that the lowest unoccupied molecular orbital (LUMO) level of Cn-PicDIs gradually lowered upon the elongation of the alkyl chains, suggesting that the alkyl chains modify intermolecular interactions between the Cn-PicDI molecules in thin films. The present results provide a new strategy for constructing a high performance n-channel organic semiconductor material by utilizing the electronic features of phenacenes

Two cytotoxic squalene-derived polyethers from the Japanese red alga Chondria armata

The red alga Chondria armata is known to produce and contain a rich diversity of secondary metabolites, such as domoic acid-related alkaloids and triterpene polyethers. Our investigation on red alga C. armata from Kagoshima coast, Japan, resulted in the isolation of two new triterpene polyethers, bandokorols A (1) and B (2). The structures of these compounds were determined based on spectroscopic data such as infrared (FTIR), 1H-NMR, APT, 1H–1H-COSY, HSQC, HMBC, NOESY and FAB mass spectrometry (HRFABMS). The anticancer potentials of these compounds were tested against adult T-cell leukaemia (ATL), S1T cells and their IC50 values are reported here

Composition and Monthly Changes of the Volatile Constituents in the Sour Hetsuka-daidai Citrus Peel

Sour citrus are prized for their flavor and fragrance. This work identified the components of the peel oil of Hetsuka-daidai (Citrus sp. hetsukadaidai), a special sour citrus that is native to the southern part of the Osumi peninsula, Kagoshima, Japan. These compounds were compared to those identified from the peels of six other major sour citrus: lime (Citrus latifolia), lemon (Citrus limon), Yuzu (Citrus junos), Kabusu (Citrus aurantium), Kabosu (Citrus sphaerocarpa), and Sudachi (Citrus sudachi). Peel oil contents were analyzed for the duration of four months during harvest season to investigate the differences in peel oil/ fragrance during ripening. These results could facilitate the development of preferred flavor and scent profiles using local species

Visible light-driven dye-sensitized photocatalytic hydrogen production by porphyrin and its cyclic dimer and trimer: effect of multi-pyridyl-anchoring groups on photocatalytic activity and stability

The monomer, dimer, and trimer of 5,15-diphenyl-10,20-di(pyridin-4-yl)porphyrin are used to investigate the multianchoring effect on TiO2 for visible light-driven photocatalytic hydrogen production in a water medium. Further, the porphyrin trimer is prepared and analyzed by nuclear magnetic resonance (NMR) spectroscopy, absorption spectroscopy, electrochemical voltammetry, fast atom bombardment (FAB) mass spectroscopy, and density functional theory (DFT) computation. The results of this study indicate that the peak intensities of the absorption spectra increase as the number of porphyrin units increases, while changes could be barely observed in the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gaps. The porphyrin dimer in a 1 wt % Pt-loaded TiO2 powder photocatalyst system exhibited optimal hydrogen production performance in a stable state over a period of 80 h and at a superior rate of 1023 μmol·g–1·h–1. Further, the stability of the photocatalytic system was systematically investigated using films containing dyes on 1 wt % Pt-loaded TiO2/FTO. For a film containing the dimer, almost no change was observed in the hydrogen-bond coordination mode of the dimer and the photocurrent during the photocatalytic reaction. However, the photocurrents of the monomer and trimer were altered during visible light irradiation without altering the coordination mode, indicating that the arrangements and orientations of the porphyrins on TiO2 surfaces were altered. These results indicate that the presence of multiple anchoring groups enhance the stability of the photocatalytic system and the rate of hydrogen production

Five amino acid residues in cysteine-rich domain of human T1R3 were involved in the response for sweet-tasting protein, thaumatin.

Thaumatin, a sweet-tasting plant protein, elicits a sweet taste sensation at 50 nM in humans but not rodents. Although it was shown that the cysteine-rich domain (CRD) of human T1R3 (hT1R3) is important for the response to thaumatin, the amino acid residues within CRD critical for response are still unknown. A comparison of the amino acid sequence (69 amino acid residues) of CRD between hT1R3 and mouse T1R3 (mT1R3) revealed sixteen amino acids that differ. In the present study, we converted each of these sixteen amino acids in hT1R3 to their mouse counterpart and examined the response to thaumatin and sucralose using a cell-based assay. No significant decrease in the response to sucralose was seen among any of the sixteen mutants. However, five mutants (Q504K, A537T, R556P, S559P, and R560K) exhibited a significantly diminished response to thaumatin. The five critical residues involved in the response to thaumatin were dispersed in the CRD of hT1R3 and widely distributed when compared to brazzein. The unique intense sweet-taste of thaumatin might be attributed to the different receptor activation mechanism compared to the small molecule sweetener sucralose

Synthesis of [7]phenacene incorporating tetradecyl chains in the axis positions and its application in field-effect transistors

Field-effect transistors (FETs) were fabricated using a new type of phenacene molecule, 3,12-ditetradecyl[7]phenacene ((C14H29)2-[7]phenacene), and solid gate dielectrics or an electric double layer (EDL) capacitor with an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate (bmim[PF6])). The new molecule, (C14H29)2-[7]phenacene, was efficiently synthesized via the Mallory photoreaction. Its crystal structure and electronic properties were determined, using X-ray diffraction, scanning tunneling microscopy/spectroscopy (STM and STS), absorption spectroscopy, and photoelectron yield spectroscopy, which showed a monoclinic crystal lattice (space group P21 (no. 4)) and an energy gap of ∼3.0 eV. The STM image clearly showed the molecular structure of (C14H29)2-[7]phenacene, as well as the closed molecular stacking, indicative of a strong fastener effect between alkyl chains. The X-ray diffraction pattern of thin films of (C14H29)2-[7]phenacene formed on a SiO2/Si substrate suggested that the molecule stood on the surface with an inclined angle of 30° with respect to the normal axis of the surface. The FET properties were recorded in two-terminal measurement mode, showing p-channel normally-off characteristics. The averaged values of field-effect mobility, μ, were 1.6(3) cm2 V−1 s−1 for a (C14H29)2-[7]phenacene thin-film FET with a SiO2 gate dielectric and 6(4) × 10−1 cm2 V−1 s−1 for a (C14H29)2-[7]phenacene thin-film EDL FET with bmim[PF6]. Thus, higher FET performance was obtained with an FET using a thin film of (C14H29)2-[7]phenacene compared to parent [7]phenacene. This study could pioneer an avenue for the realization of high-performance FETs through the addition of alkyl chains to phenacene molecules

Aaptamine-related alkaloid from the marine sponge Aaptos aaptos

A new aaptamine-related alkaloid, 1,3-dioxolo [4,5-d] benzo [de]-1,6-naphthyridine (methylenedioxyaaptamine, 1), was isolated from the organic extracts of the Bornean marine sponge Aaptos aaptos, together with a known aaptamine derivative, 8,9,9-trimethoxy-9H-benzo [de]-1,6-naphthyridine (2). The structure of compound 1 was elucidated by interpretation of its spectroscopic data. Two compounds were tested for their cytotoxic potentials against adult T-cell leukemia (ATL) cells, and compound 1 showed moderate cytotoxic potential

Atomic structure of the sweet-tasting protein thaumatin I at pH 8.0 reveals the large disulfide-rich region in domain II to be sensitive to a pH change.

Thaumatin, an intensely sweet-tasting plant protein, elicits a sweet taste at 50 nM. Although the sweetness remains when thaumatin is heated at 80 °C for 4h under acid conditions, it rapidly declines when heating at a pH above 6.5. To clarify the structural difference at high pH, the atomic structure of a recombinant thaumatin I at pH 8.0 was determined at a resolution of 1.0Å. Comparison to the crystal structure of thaumatin at pH 7.3 and 7.0 revealed the root-mean square deviation value of a Cα atom to be substantially greater in the large disulfide-rich region of domain II, especially residues 154-164, suggesting that a loop region in domain II to be affected by solvent conditions. Furthermore, B-factors of Lys137, Lys163, and Lys187 were significantly affected by pH change, suggesting that a striking increase in the mobility of these lysine residues, which could facilitate a reaction with a free sulfhydryl residue produced via the β-elimination of disulfide bonds by heating at a pH above 7.0. The increase in mobility of lysine residues as well as a loop region in domain II might play an important role in the heat-induced aggregation of thaumatin above pH 7.0

Atomic structure of recombinant thaumatin II reveals flexible conformations in two residues critical for sweetness and three consecutive glycine residues.

Thaumatin, an intensely sweet-tasting protein used as a sweetener, elicits a sweet taste at 50 nM. Although two major variants designated thaumatin I and thaumatin II exist in plants, there have been few dedicated thaumatin II structural studies and, to date, data beyond atomic resolution had not been obtained. To identify the detailed structural properties explaining why thaumatin elicits a sweet taste, the structure of recombinant thaumatin II was determined at the resolution of 0.99 Å. Atomic resolution structural analysis with riding hydrogen atoms illustrated the differences in the direction of the side-chains more precisely and the electron density maps of the C-terminal regions were markedly improved. Though it had been suggested that the three consecutive glycine residues (G142-G143-G144) have highly flexible conformations, G143, the central glycine residue was successfully modelled in two conformations for the first time. Furthermore, the side chain r.m.s.d. values for two residues (R67 and R82) critical for sweetness exhibited substantially higher values, suggesting that these residues are highly disordered. These results demonstrated that the flexible conformations in two critical residues favoring their interaction with sweet taste receptors are prominent features of the intensely sweet taste of thaumatin