Catechol-derived Inhibitors against Quorum Sensing from Retiboletus kauffmanii

[Objectives]This study aimed to screen anti-quorum sensing(QS)activity from the constituent of Retiboletus kauffmanii fruit body.[Methods]Chromatographic technology was used to isolate compounds,while well diffusion assay was applied to screen anti-quorum sensing activity.[Results]12 phenolic compounds were purified from extracts,three catechol-derived compounds at sub-inhibitory concentrations were found to inhibit the production of violacein in Chromobacterium violaceum for the first time.[Conclusions]Three catechol analogs isolated from R.kauffmanii fruit body extract were indicated as quorum sensing inhibitors against C.violaceum.

Antibiotic Metabolites from the Coral-Associated Actinomycete Streptomyces sp. OUCMDZ-1703

From the oligotrophic culture of a soft coral-associated actinomycetes strain, Streptomyces sp. OUCMDZ-1703, we isolated and identified two new chlorinated polyketides that we named strepchloritides A and B （1 and 2）, three thiazole derivatives known as watasemycin A （3）, pulicatin G （4） and aerugine （5）, along with pyrrole- 2-carboxamide, furan-2-carboxamide and 1-（3,5-dihydroxyphenyl）ethanone. The new structures of 1 and 2 were determined by spectroscopic studies such as 1D- and 2D-NMR and MS analyses, while the known compounds were identified by comparison of the NMR data with those in literatures. The results showed that actinomycete strain OUCMDZ-1703 could use the relative high ratio of chlorine in the oligotrophic medium to synthesize chlorinated natural products. New compounds 1 and 2 displayed cytotoxicity against the MCF-7 ceils with ICs0 values of 9.9 and 20.2 ~tmoloL-1, respectively. Thiazole derivatives 3 and 5 were first found to be active against three clinical strains of methicillin-resistant Staphylococcus aureus （MRSA082, MRSA111 and MRSA234） with the same MIC/MBC values of 7.81/7.81 μg·mL-1.

Effect of solvent on directional drift in Brownian motion of particle/molecule with broken symmetry

The directional drifting of particles/molecules with broken symmetry has received increasing attention. Through molecular dynamics simulations, we investigate the effects of various solvents on the time-dependent directional drifting of a particle with broken symmetry. Our simulations show that the distance of directional drift of the asymmetrical particle is reduced while the ratio of the drift to the mean displacement of the particle is enhanced with increasing mass, size, and interaction strength of the solvent atoms in a short time range. Among the parameters considered, solvent atom size is a particularly influential factor for enhancing the directional drift of asymmetrical particles, while the effects of the interaction strength and the mass of the solvent atoms are relatively weaker. These findings are of great importance to the understanding and control of the Brownian motion of particles in various physical, chemical, and biological processes within finite time spans.