Atom transfer radical polymerization was employed to induce the living polymerization of an azobenzene-containing monomer, 10-[4-(4-hexyl­phenylazo)­phenoxy]­decyl acrylate, with the resulting polyacrylate and the corresponding polymethacrylate undergoing a reversible solid–liquid phase transition under isothermal conditions caused by the photoinduced change of the azobenzene moiety shape. Irradiation-induced property changes were investigated by nuclear magnetic resonance, ultraviolet–visible (UV–vis) absorption spectroscopy, and dynamic viscoelasticity measurements, with focus on the effects of the main chain chemical structure and molecular weight. Azobenzene moiety photoisomerization and the concomitant phase transition were faster for the polyacrylate than for the polymethacrylate, which indicated the strong influence of the main chain structure. Finally, phototuning of the adhesion strength using azopolymer-bonded glass substrates was studied by single lap shear tests, with the maximum adhesion strength of >3 MPa being comparable to that of commercial hot-melt adhesives. Irradiation with UV light for only 15 s lowered the adhesion strength to <0.2 MPa, allowing easy debonding upon the application of a small force.

Photocurable adhesives based on polymers and resins are an integral part of different production processes because of their fast curing and local area bonding ability. Recently, dismantlable adhesives have attracted a lot of attention for recycling adherends or replacement of adhesion defects. However, adhesives that allow repeatable bonding and debonding solely by light irradiation, i.e., without heat activation, are lacking. Here, ABA-type triblock copolymers consisting of poly(meth)acrylates bearing an azobenzene moiety (A block) and 2-ethylhexyl (B block) side chains were synthesized and utilized as photocurable adhesives. In contrast to the azo homopolymers, the block copolymer structure and incorporation of the soft middle block actualized a low concentration of the azobenzene moiety and consequently, higher flexibility of the resultant copolymers. This enabled film formation of the azobenzene-based adhesives and light-induced bonding for the first time. On the basis of the photoisomerization of the azobenzene moiety, changes in their viscoelastic property, i.e., softening and hardening, were induced by UV irradiation at 365 nm (50-100 mW cm) and green light irradiation at 520 nm (40 mW cm), respectively. In fact, two glass substrates were bonded with the self-standing polymer film, which was sequentially softened and hardened upon UV and green light irradiations. They exhibited shear strengths of 1.5-2.0 MPa, and UV irradiation lowered the adhesion strength to 0.5-0.1 MPa. Interestingly, the repeatable bonding and debonding abilities of the polymers were accomplished without loss of the adhesion strength.

Glucuronoxylanases are endo-xylanases and members of the glycoside hydrolase family 30 subfamilies 7 (GH30-7) and 8 (GH30-8). Unlike for the well-studied GH30-8 enzymes, the structural and functional characteristics of GH30-7 enzymes remain poorly understood. Here, we report the catalytic properties and three-dimensional structure of GH30-7 xylanase B (Xyn30B) identified from the cellulolytic fungus Talaromyces cellulolyticus. Xyn30B efficiently degraded glucuronoxylan to acidic xylooligosaccharides (XOSs), including an ␣-1,2-linked 4-O-methyl-D-glucuronosyl substituent (MeGlcA). Rapid analysis with negative-mode electrospray-ionization multistage MS (ESI(؊)-MS n ) revealed that the structures of the acidic XOS products are the same as those of the hydrolysates (MeGlcA 2 Xyl n , n > 2) obtained with typical glucuronoxylanases. Acidic XOS products were further degraded by Xyn30B, releasing first xylobiose and then xylotetraose and xylohexaose as transglycosylation products. This hydrolase reaction was unique to Xyn30B, and the substrate was cleaved at the xylobiose unit from its nonreducing end, indicating that Xyn30B is a bifunctional enzyme possessing both endo-glucuronoxylanase and exo-xylobiohydrolase activities. The crystal structure of Xyn30B was determined as the first structure of a GH30-7 xylanase at 2.25 Å resolution, revealing that Xyn30B is composed of a pseudo-(␣/␤) 8catalytic domain, lacking an ␣6 helix, and a small ␤-rich domain. This structure and site-directed mutagenesis clarified that Arg 46 , conserved in GH30-7 glucuronoxylanases, is a critical residue for MeGlcA appendage-dependent xylan degradation. The structural comparison between Xyn30B and the GH30-8 enzymes suggests that Asn 93 in the ␤2-␣2 loop is involved in xylobiohydrolase activity. In summary, our findings indicate that Xyn30B is a bifunctional endo-and exo-xylanase.The authors declare that they have no conflicts of interest with the contents of this article. This article contains Table S1 and Figs. S1-S6. The atomic coordinates and structure factors (code 6IUJ) have been deposited in the Protein Data Bank (http://wwpdb.org/).

The objective of this study was to clarify variations of the ceramide (CER) profile in human stratum corneum (SC) in different seasons and in different regions of the body and to estimate the contributions of CERs to the SC barrier and water-holding functions. Based on the information that there are great variations of SC functions among body sites, we compared the CER profiles obtained from ten different anatomical sites in healthy Japanese males in four seasons. Not only the physiological parameters of skin but also the CER profile showed body region and seasonal variations. The total CER level, the CER composition and the C34-CER[NS] species displayed strong correlations with the values of transepidermal water loss and capacitance throughout the body. Especially in the cheek, a strong correlation between the capacitance and the CER profile was observed. There were seasonal variations of the CER profile in the lip, upper arm and palm. Our results indicate that regional and seasonal variations of the CER profile may contribute to SC functions.

The general utility of a 1,1-diphenylethylene (DPE) derivative substituted with trimethylsilyl-and tert-butyldimethylsilylprotected hydroxyl functionalities, as a new dual-functionalized core agent in conjunction with a living anionic polymerization system, has been demonstrated by the successful synthesis of various well-defined 3arm ABC and 4-arm ABCD μ-star polymers. Two different protected hydroxyl functionalities were progressively deprotected to generate hydroxyl groups, followed by conversion to α-phenyl acrylate (PA) functions at separate stages, and the PA functions were reacted with appropriate living anionic polymers to result in the above μ-stars. In order to further synthesize μ-star polymers with five or more arms, a new iterative methodology using a functional DPE anion derived from the above DPE derivative has been developed. The reaction system of this methodology is designed in such a way that the PA function used as the reaction site is regenerated after the introduction of an arm segment in each reaction sequence, and this sequence, consisting of "arm introduction and regeneration of the PA reaction site", is repeatable. With this methodology, a series of new well-defined μ-star polymers up to a 5arm ABCDE type, composed of all different methacrylate-based polymer segments, were successfully synthesized for the first time.