The helix-forming nature of β-1,3-glucan polysaccharides is a characteristic that has potential for producing gene carriers, bio-nanomaterials and other chiral nanowires. Herein, carboxylic curdlan (CurCOOH) bearing the β-1,3-polyglucuronic acid structure was successfully prepared from β-1,3-glucan polysaccharide curdlan (Cur) by one-step oxidation using a 4-acetamido-TEMPO/NaClO/NaClO(2) system as the oxidant. The resulting high-molecular-weight CurCOOH was proved to bear the 6-COOH group in 100% purity. The optical rotatory dispersion (ORD) spectra indicated that the obtained CurCOOH behaves as a water-soluble single-strand in various pH aqueous media. This advantage has allowed us to use CurCOOH as a polymeric host to form various macromolecular complexes. For example, complexation of CurCOOH with single-walled carbon nanotubes (SWNTs) resulted in a water-soluble one-dimensional architecture, which formed a dispersion in aqueous solution that was stable for several months, and much more stable than SWNTs complexes of the similar negatively-charged polyacrylic acid (PAA) and polymethacrylic acid (PMAA). It was shown that in the complex, SWNTs are effectively wrapped by a small amount of CurCOOH, enabling them to avoid electrostatic repulsion. This pH-responsive CurCOOH formed a very stable complex with cationic water-soluble polythiophenes (PT-1), which was stabilized not only by the hydrophobic interaction but also by the electrostatic attraction between trimethylammonium cations in PT-1 and dissociated anionic COO(-) groups in CurCOOH. The included PT-1 became CD-active only in the neutral to basic pH region, and the positive Cotton effect suggested that the conjugated main chain is twisted in the right-handed direction. We also found that CurCOOH can interact with polycytidylic acid (poly(C)) only under high NaCl concentrations, the binding and release of which could be controlled by a change in the salt concentration. We believe, therefore, that CurCOOH bearing a dissociable COOH group can act as a new potential polymeric host to construct novel polymeric complexes applicable for gene carriers, biosensors, chiral polymer assemblies, etc.

Amphoteric β-1,3-glucans possessing both amino groups and carboxylic acid groups on the C6 positions of glucose units were designed and synthesized from naturally produced curdlan. The amphoteric polysaccharides showed the isoelectric point and the pH responsive interconversion between the original triple helix and single-stranded random structures. Since the pH dependences are comparable to the typical properties of proteins, the polysaccharides can be considered as a new class of giant amino acids. Utilizing the pH responsiveness, pH-controlled catch-and-release has been realized for cationic peptides or anionic DNA. We believe that the amphoteric polysaccharide can act as a new potential polymer to construct stimuli-responsive smart materials on the basis of the polysaccharide scaffold.

A Frontier Molecular Orbital (FMO) analysis is not so effective for the singlet peri-, site-, regio-and stereoselectivities of singlet photodimerization (anti-3,6-[4+4] cycloaddition for 3) of 2-pyridone (1) and for the cross additions (mainly endo-3,4-ht-[2+2] cycloaddition for 4) with acrylates (2). Their Origins were analysed by transition state (TS) analysis of whole reaction (TS 1 , TS 2 , TS 3) using MOPAC-PM5 and UCIS/6-31+G(d)//PM5 levels of calculation, and the major factors of the selectivities were inferred quantitatively. The singlet reactions may be concerted, controlled by TS 1 , and may be competed by orbital overlapping and ionic factors. The Origin for a novel adduct, azocinone (5) between excited singlet 1 and 2 was also estimated by PM5 simulation. The triplet and regioselective cross additions (mainly exo-5,6-hh-[2+2] cycloaddition for 7) between 1 and 2 were inferred to be two-step reactions, and to pass through twisted biradicals, with the first-step transition TS 1 energy smaller than the second-step one. The energy of TS 2 (ring-closure) was lower than that of TS 3 (bond-cleavage).

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Exchange bias (EB) has been a hot research topic since its discovery in the 1950s. In this paper, we present the peculiar temperature dependence of perpendicular EB in Pt/Co/Au/Cr 2 O 3 /Pt stacked films: the regeneration of the EB in the high temperature regime. Three temperature-dependent states are identified: (1) low temperature exchange-biased state, (2) middle temperature coercivity-enhanced state, and (3) high temperature regenerated exchange-biased state. At the boundary of these states, both EB field (H EB ) and coercivity (H C ) abruptly switch with the relationship H EB = ΔH C . The low temperature disappearance of EB can be interpreted based on the classical Meiklejohn-Bean exchange anisotropy model. A more complex temperature dependence of the interfacial spin alignment and magnetic domain wall width in the Cr 2 O 3 layer is involved in the high temperature regeneration of EB. © 2020 The Japan Society of Applied Physics 3. Results and discussions 3.1. Epitaxial growth Typical sets of RHEED images are shown in Fig. 2. The RHEED patterns of the Pt buffer surface and the Cr 2 O 3 surface appear streaky, indicating the smooth surface of these layers. The diffraction patterns suggest the growth of Pt(111) and Cr 2 O 3 (0001). The 〈1120〉 substrate -azimuthal RHEED patterns for Pt(111) and Cr 2 O 3 (0001) [Fig. 2(b)] are both