Neuroglobin (Ngb) is a newly discovered vertebrate heme protein that is expressed in the brain and can reversibly bind oxygen. It has been reported that Ngb expression levels increase in response to oxygen deprivation and that it protects neurons from hypoxia in vitro and in vivo. However, the mechanism of this neuroprotection remains unclear. In the present study, we tried to clarify the neuroprotective role of Ngb under oxidative stress in vitro. By surface plasmon resonance, we found that ferric Ngb, which is generated spontaneously as a result of the rapid autoxidation, binds exclusively to the GDP-bound form of the ␣ subunit of heterotrimeric G protein (G␣ i ). In GDP dissociation assays or guanosine 5-O-(3-thio)triphosphate binding assays, ferric Ngb behaved as a guanine nucleotide dissociation inhibitor (GDI), inhibiting the rate of exchange of GDP for GTP. The interaction of GDP-bound G␣ i with ferric Ngb will liberate G␤␥, leading to protection against neuronal death. In contrast, ferrous ligand-bound Ngb under normoxia did not have GDI activities. Taken together, we propose that human Ngb may be a novel oxidative stress-responsive sensor for signal transduction in the brain.

Nineteen-hour variation of postural sway, alertness and rectal temperature during sleep deprivation were studied. Alertness decreased gradually at night and remained low until morning. Postural sway in the eyes-closed condition increased during early morning. In six of the eight subjects the greatest sway was observed during the 3-h period when rectal temperature was at its minimum. It is suggested that unbearable sleepiness during sleep deprivation will give rise to measurable impairment of postural balance especially during the time zone of temperature nadir.

Tardigrades are able to tolerate almost complete dehydration by entering a reversible ametabolic state called anhydrobiosis and resume their animation upon rehydration. Dehydrated tardigrades are exceptionally stable and withstand various physical extremes. Although trehalose and late embryogenesis abundant (LEA) proteins have been extensively studied as potent protectants against dehydration in other anhydrobiotic organisms, tardigrades produce high amounts of tardigrade-unique protective proteins. Cytoplasmic-abundant heat-soluble (CAHS) proteins are uniquely invented in the lineage of eutardigrades, a major class of the phylum Tardigrada and are essential for their anhydrobiotic survival. However, the precise mechanisms of their action in this protective role are not fully understood. In the present study, we first postulated the presence of tolerance proteins that form protective condensates via phase separation in a stress-dependent manner and searched for tardigrade proteins that reversibly form condensates upon dehydration-like stress. Through a comprehensive search using a desolvating agent, trifluoroethanol (TFE), we identified 336 proteins, collectively dubbed “TFE-Dependent ReversiblY condensing Proteins (T-DRYPs).” Unexpectedly, we rediscovered CAHS proteins as highly enriched in T-DRYPs, 3 of which were major components of T-DRYPs. We revealed that these CAHS proteins reversibly polymerize into many cytoskeleton-like filaments depending on hyperosmotic stress in cultured cells and undergo reversible gel-transition in vitro. Furthermore, CAHS proteins increased cell stiffness in a hyperosmotic stress-dependent manner and counteract the cell shrinkage caused by osmotic pressure, and even improved the survival against hyperosmotic stress. The conserved putative helical C-terminal region is necessary and sufficient for filament formation by CAHS proteins, and mutations disrupting the secondary structure of this region impaired both the filament formation and the gel transition. On the basis of these results, we propose that CAHS proteins are novel cytoskeleton-like proteins that form filamentous networks and undergo gel-transition in a stress-dependent manner to provide on-demand physical stabilization of cell integrity against deformative forces during dehydration and could contribute to the exceptional physical stability in a dehydrated state.

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With the aim of developing new 1D platinum chain solids having infinite Pt-Pt bonds, several carboxylate-bridged cis-diammineplatinum dimers have been prepared and structurally characterized. For a dimer doubly bridged with acetates, five different salts [Pt 2 (NH 3 ) 4 (µ-CH 3 CO 2 ) 2 ]X 2 ‚nH 2 O (X 2 , n ) (ClO 4 ) 2 , 2, 1; (NO 3 ) 2 , 1, 2; (BF 4 ) 2 , 4, 3; (PF 6 ) 2 , 2, 4; (SiF 6 ), 4, 5) have been prepared. The crystal structure of 5 has revealed that an infinite dimer chain [Pt 2 (NH 3 ) 4 (µ-CH 3 CO 2 ) 2 ] n 2n+ can be given as a result of hydrogen bond formation between the ammines and the oxygen atoms of acetates, demonstrating our prediction that the N 2 O 2 coordination sphere may serve as a hydrogen-bonding moiety to assist formation of an infinite dimer chain. An asymmetric dimer bridged by both acetate and hydroxide ligands, [Pt 2 (NH 3 ) 4 (µ-CH 3 CO 2 )(µ-OH)](SiF 6 ) (6), has also been isolated as a byproduct of 5, and a similar 1D framework, [Pt 2 (NH 3 ) 4 (µ-CH 3 CO 2 )(µ-OH)] n 2n+ , has been characterized by X-ray diffraction. In addition, some glycolate-bridged analogues of similar frameworks have been synthesized and characterized: [Pt 2 (NH 3 ) 4 (µ-CH 2 (OH)CO 2 ) 2 ](SiF 6 )‚4H 2 O (7), [Pt 2 (NH 3 ) 4 (µ-CH 2 -(OH)CO 2 ) 2 ](ClO 4 ) 2 ‚H 2 O (8), and [Pt 2 (NH 3 ) 4 (µ-CH 2 (OH)CO 2 )(µ-OH)](NO 3