4-Hydroxy-3-methyl-2(1H)-quinolone, originally discovered from a Brassicaceae plant, produced by a soil bacterium of the genus Burkholderia sp.: determination of a preferred tautomer and antioxidant activity.

4-Hydroxy-3-methyl-2(1H)-quinolone (1), a molecule known for a long time and recently discovered from a Brassicaceae plant Isatis tinctoria without providing sufficient evidence to support the structure, was isolated from a fermentation extract of Burkholderia sp. 3Y-MMP isolated from a soil by a Zn2+ enrichment culture. Detailed spectroscopic analyses by MS and NMR, combined with 13C chemical shift comparison with literature values of the related compounds and a synthetic preparation of 1, allowed its first full NMR characterization and identification of 2-quinolone but not 2-quinolinol (2) as the preferred tautomer for this heterocyclic system. While the metal-chelating activity was negligible, compound 1 at 10 µM, a concentration lower than that in liquid production cultures, quenched hydroxy radical-induced chemiluminescence emitted by luminol by 86%. Because some Burkholderia species are pathogenic to plants and animals, the above result suggests that 1 is a potential antioxidant to counteract reactive oxygen species-based immune response in the host organisms.

Phaeolschidin F, a new symmetrical bis(styrylpyrone) derivative with redox-catalyzing activity from the mushroom Gymnopilus aeruginosus (order Agaricales).

Phaeolschidin F (1) was isolated from fruiting bodies of the bitter and toxic mushroom Gymnopilus aeruginosus. Structure analysis by NMR and MS revealed that 1 is a new symmetrical bis(styrylpyrone). A series of anti-oxidant and pro-oxidant tests characterized that 1 is a redox catalyst having more anti-oxidant and less pro-oxidant activities than quercetin.

Suppression of colonic oxidative stress caused by chronic ethanol administration and attenuation of ethanol-induced colitis and gut leakiness by oral administration of sesaminol in mice.

Chronic consumption of excess ethanol is one of the major risk factors for colorectal cancer (CRC), and the pathogenesis of ethanol-related CRC (ER-CRC) involves ethanol-induced oxidative-stress and inflammation in the colon and rectum, as well as gut leakiness. In this study, we hypothesised that oral administration of sesaminol, a sesame lignan, lowers the risk of ER-CRC because we found that it is a strong antioxidant with very low prooxidant activity. This hypothesis was examined using a mouse model, in which 2.0% v/v ethanol was administered ad libitum for 2 weeks with or without oral gavage with sesaminol (2.5 mg per day). Oral sesaminol administration suppressed the ethanol-induced colonic lesions and the ethanol-induced elevation of the colonic levels of oxidative stress markers (8-hydroxy-2'-deoxyguanosine, malondialdehyde, and 4-hydroxyalkenals). It consistently suppressed the chronic ethanol-induced expressions of cytochrome P450-2E1 and inducible nitric oxide synthase and upregulated heme oxygenase-1 expression, probably via the nuclear factor erythroid-derived 2-like 2 pathway in the mouse colon. Oral sesaminol administration also suppressed the chronic ethanol-induced elevation of colonic inflammation marker levels, such as those of tumour necrosis factor-α, interleukin-6, and monocyte chemoattractant protein-1, probably via the nuclear factor-kappa B pathway. Moreover, it prevented the chronic ethanol-induced gut leakiness by restoring tight junction proteins, giving rise to lower plasma endotoxin levels compared with those of ethanol-administered mice. All of these results suggest that dietary supplementation of sesaminol may lower the risk of ER-CRC by suppressing each of the above-mentioned steps in ER-CRC pathogenesis.

Squeezing visible light waves into a 3-nm-thick and 55-nm-long plasmon cavity.

We demonstrate controlled squeezing of visible light waves into nanometer-sized optical cavities. The light is perpendicularly confined in a few-nanometer-thick SiO2 film sandwiched between Au claddings in the form of surface plasmon polaritons and exhibits Fabry-Perot resonances in a longitudinal direction. As the thickness of the dielectric core is reduced, the plasmon wavelength becomes shorter; then a smaller cavity is realized. A dispersion relation down to a surface plasmon wavelength of 51 nm for a red light, which is less than 8% of the free-space wavelength, was experimentally observed. Any obvious breakdowns of the macroscopic electromagnetics based on continuous dielectric media were not disclosed for 3-nm-thick cores.

Combination of Dsb coexpression and an addition of sorbitol markedly enhanced soluble expression of single-chain Fv in Escherichia coli.

Many eukaryotic proteins have been produced successfully in Escherichia coli. However, not every gene can be expressed efficiently in this organism. Most proteins, especially those with multiple disulfide bonds, have been shown to form insoluble protein or inclusion body in E. coli. An inactive form of protein would require an in vitro refolding step to regain biological functions. In this study, we described the system for soluble expression of a single-chain variable fragment (scFv) against hepatocellular carcinoma (Hep27scFv) by coexpressing Dsb protein and enhancing with medium additives. The results revealed that overexpression of DsbABCD protein showed marked effect on the soluble production of Hep27scFv, presumably facilitating correct folding. The optimal condition for soluble scFv expression could be obtained by adding 0.5M sorbitol to the culture medium. The competitive enzyme-linked immunosorbent assay (ELISA) indicated that soluble scFv expressed by our method retains binding activity toward the same epitope on a hepatocellular carcinoma cell line (HCC-S102) recognized by intact antibody (Ab) (Hep27 Mab). Here, we report an effective method for soluble expression of scFv in E. coli by the Dsb coexpression system with the addition of sorbitol medium additive. This method might be applicable for high-yield soluble expression of proteins with multiple disulfide bonds.

Production of brain-derived neurotrophic factor in Escherichia coli by coexpression of Dsb proteins.

When brain-derived neurotrophic factor (BDNF) is produced in the Escherichia coli periplasm, insoluble BDNF proteins with low biological activity and having mismatched disulfide linkages are formed. The coexpression of cysteine oxidoreductases (DsbA and DsbC) and membrane-bound enzymes (DsbB and DsbD), which play an important role in the formation of disulfide bonds in the periplasm, was investigated to improve the production of soluble and biologically active BDNF. The expression levels of Dsb proteins changed when the growth medium and the Dsb expression plasmids were changed, and the production rate of soluble BDNF was almost proportional to the expression level of DsbC protein with disulfide isomerase activity in the case of a low expression level of BDNF. The rate of soluble BDNF production with coexpression of DsbABCD was as high as 35%. These results show that coexpression of BDNF and Dsb proteins can effectively increase the production of soluble and biologically active BDNF.