Picking up the thread: A large, reversible change in size as well as shape is observed in a [2]pseudorotaxane‐based molecular machine composed of cucurbit[8]uril (CB[8]; bead) and a hexamethylene‐bridged bisviologen (thread, see schematic representation) on application of external stimuli. The key feature of the machinelike behavior is the reversible formation of a molecular loop by intramolecular pairing of the terminal viologen radical cation units inside CB[8] upon electrochemical or photochemical reduction.
Hydroquinone (HQ) functions as a skin-whitening agent, but it has the potential to cause dermatitis. We synthesized a HQ fructoside (HQ-Fru) as a potential skin-whitening agent by reacting levansucrase from Leuconostoc mesenteroides with HQ as an acceptor and sucrose as a fructofuranose donor. The product was purified using 1-butanol partition and silica-gel column chromatography. The structure of the purified HQ-Fru was determined by (1)H and (13)C nuclear magnetic resonance, and the molecular ion of the product was observed at m/z 295 (C12 H16 O7 Na)(+). The HQ-Fru was identified as 4-hydroxyphenyl-beta-D: -fructofuranoside. The optimum condition for HQ-Fru synthesis was determined using a response surface method (RSM), and the final optimum condition was 350 mM HQ, 115 mM sucrose, and 0.70 U/ml levansucrase, and the final HQ-Fru produced was 1.09 g/l. HQ-Fru showed anti-oxidation activities and inhibition against tyrosinase. The median inhibition concentration (IC(50)) of 1,1-diphenyl-2-picrylhydrazyl scavenging activity was 5.83 mM, showing higher antioxidant activity compared to beta-arbutin (IC(50) = 6.04 mM). The K ( i ) value of HQ-Fru (1.53 mM) against tyrosinase was smaller than that of beta-arbutin (K ( i ) = 2.8 mM), indicating that it was 1.8-times better as an inhibitor. The inhibition of lipid peroxidation by HQ-Fru was 105.3% that of HQ (100%) and 118.9 times higher than that of beta-arbutin (0.89% of HQ).
A water-developable negative photoresist based on the photocrosslinking of N-phenylamide groups was prepared by the copolymerization of 4-styrenesulfonic acid sodium salts (SSS) with N-phenylmethacrylamide (copolymer A) or p-hydroxy-N-phenylmethacrylamide (copolymer B), and its properties such as solubility changes, photochemical reaction, and photoresist characteristics were studied. The copolymer containing a relatively higher amount of SSS units was soluble in water. Solubility changes of the copolymers in the various buffer solutions of pH 4 ϳ 11 and in water upon irradiation were observed by the measurement of insoluble fraction. The copolymers were soluble in water before irradiation, whereas they became insoluble upon irradiation with the UV light of 254 nm. The photochemical reaction of the copolymer studied by the UV and IR absorption spectroscopies indicated that a photoFries rearrangement was favored for copolymer A, whereas a photocrosslinking reaction was predominate for copolymer B. Resist properties of the copolymers were studied by measurement of the normalized thickness and by development of the micropattern. Negative tone images with a resolution of 1 m were obtained with these materials that have a sensitivity (D g 0.5 ) of ϳ 1100 mJ/cm 2 with an aqueous developing process.
Two arbutin glucosides were synthesized via the acceptor reaction of a glucansucrase from Leuconostoc mesenteroides B-1299CB with arbutin and sucrose. The glucosides were purified by Bio-gel P-2 column chromatography and high-performance liquid chromatography, and the structures were elucidated as 4-hydroxyphenyl beta-isomaltoside (arbutin-G1), 4-hydroxyphenyl beta-isomaltotrioside (arbutin-G2), according to the results of (1)H, (13)C, heteronuclear single-quantum coherence, (1)H-(1)H COSY, and heteronuclear multiple-bond correlation analyses. Arbutin glucoside (4-hydroxyphenyl beta-isomaltoside) exhibited slower effects on 1,1-diphenyl-2-picrylhydrazyl radical scavenging and similar effects on tyrosinase inhibition, and increased inhibitory effect on matrix metalloproteinase-1 production induced by UVB than arbutin.
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