Let it shine: New hypoxia-sensitive fluorescent probes were developed; they consist of a rhodamine moiety with an azo group directly conjugated to the fluorophore. Because of an ultrafast conformational change around the NN bond, the compounds are nonfluorescent under normoxia. However, under hypoxia, the azo group is reduced, and a strongly fluorescent rhodamine derivative is released.

Triple-helical structures of (Pro-Hyp-Gly)n (n = 10, 11) at 100 K and room temperature (RT) were analyzed at 1.26 A resolution by using synchrotron radiation data. Totals of 49 and 42 water molecules per seven triplets in an asymmetric unit were found for the structures at 100 K and RT, respectively. These water molecules were classified into two groups, those in the first and second hydration shells. Although there was no significant difference between water molecules in the first shell at 100 K and those at RT, a significant difference between those in the second shell was observed. That is, the number of water molecules at RT decreased to one half and the average distance from peptide chains at RT became longer by about 0.3 A. On the other hand, of seven triplets in an asymmetric unit, three proline residues at the X position at 100 K clearly showed an up-puckering conformation, as opposed to the recent propensity-based hypothesis for the stabilization and destabilization of triple-helical structures by proline hydroxylation. This puckering was attributed to the interaction between proline rings and the surrounding water molecules at 100 K, which is much weaker at RT, as shown by longer average distance from peptide chains.

We have recently developed a new method for synthesizing polyrotaxanes with a high covering ratio, rigidity, photoluminescence efficiency, and solubility in a variety of organic solvents through the polymerization of structurally defined rotaxane monomers. The rigid rodlike structure of the pi-conjugated core polymers in these polyrotaxanes is thought to facilitate the effective transport of charge carriers. Here we applied this method to the synthesis of a polyrotaxane having a poly(phenylene ethynylene) backbone by the Sonogashira copolymerization of a structurally defined rotaxane with a linker molecule. According to time-resolved microwave conductivity and transient absorption spectroscopy measurements, the hole mobility along the pi-conjugated polymer chain of the polyrotaxane thus formed was extremely high and comparable to that in amorphous silicon.

The crystal structure of a collagen-model peptide [(Pro-Pro-Gly)(9)](3) has been determined at 1.33 A resolution. Diffraction data were collected at 100 K using synchrotron radiation, which led to the first structural study of [(Pro-Pro-Gly)(n)](3) under cryogenic conditions. The crystals belong to the P2(1) space group with cell parameters of a = 25.95, b = 26.56, c = 80.14 Angstroms and beta = 90.0 degrees. The overall molecular conformation was consistent with the left-handed 7/2-helical model with an axial repeat of 20 A for native collagen. A total of 332 water molecules were found in an asymmetric unit. Proline residues in adjacent triple-helices exhibited three types of hydrophobic interactions. Furthermore, three types of hydrogen-bonding networks mediated by water molecules were observed between adjacent triple-helices. These hydrophobic interactions and hydrogen-bonding networks occurred at intervals of 20 Angstroms along the c-axis based on the previous sub-cell structures [(Pro-Pro-Gly)(n)](3) (n = 9, 10), which were also seen in the full-cell structure of [(Pro-Pro-Gly)(10)](3). Five proline residues at the Y position in the X-Y-Gly triplet were found in a down-puckering conformation, this being inconsistent with the recently proposed propensity-based hypothesis. These proline residues were forced to adopt opposing puckering because of the prevailing hydrophobic interaction between triple-helices compared with the Pro:Pro stacking interaction within a triple-helix.

Phonons in nearly optimally doped HgBa(2)CuO(4+delta) were studied by inelastic x-ray scattering. The dispersion of the low-energy modes is well described by a shell model, while the Cu-O bond stretching mode at high energy shows strong softening towards the zone boundary, which deviates strongly from the model. This seems to be common in the hole-doped high-T(c) superconducting cuprates, and, based on this work, not related to a lattice distortion specific to each material.

Liquid phase oxidation of cumene in the absence of solvent was carried out in a bubble column in temperature range from IOO°to I3O°C. The reaction scheme in the batch-wise operation was classified in terms of three periods: the induction, the steady chain-propagation and the termination periods.The kinetics in the steady chain-propagation period, which is industrially important, was studied and the rate expressions of chemical steps were derived.

Extensive research on the use of cyclodextrin for insulating pi-conjugated polymer chains has been carried out. However, the resulting polyrotaxanes do not exhibit high and constant covering ratios and are generally insoluble in organic solvents. Here we demonstrate a new method of synthesizing permethylated cyclodextrin-based polyrotaxanes involving the polymerization of linked rotaxane monomers. The insulated molecular wires obtained by this method are highly soluble in organic solvents and have a high covering ratio, rigidity, and photoluminescence efficiency. A cholesteric liquid-crystal phase was observed for these highly rigid polyrotaxanes, in which threading of a pi-conjugated polymer chain through chiral macrocycles occurs.

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