[A new polyketide from marine-derived Streptomyces sp.MDW-06].

To isolate and identify secondary metabolites of marine-derived Streptomyces sp.MDW-06,the isolations and purifications of compounds were performed by means of column chromatography over silica gel. And their structures were elucidated through the spectroscopic analysis of MS,NMR and specific rotations. The bioactivities were assayed by paper diffusion and DPPH method. From the fermentation broth of marine-derived Streptomyces sp.MDW-06,five compounds( 1-5) were isolated and identified as streptopentanoic acid( 1),germicidin A( 2),germicidin B( 3),isogermicidin A( 4),isogermicidin B( 5) and oxohygrolidin( 6),respectively. Compound 1 is a new compound. Compound 1 shows DPPH radical scavenging activity with 36. 4% at 100 mg·L~(-1).

Ru(bpy)32+-Silica@Poly-L-lysine-Au as labels for electrochemiluminescence lysozyme aptasensor based on 3D graphene.

In this work, the feasibility of a novel sensitive electrochemiluminescence aptasensor for the detection of lysozyme using Ru(bpy)32+-Silica@Poly-L-lysine-Au (RuSiNPs@PLL-Au) nanocomposites labeling as an indicator was demonstrated. The substrate electrode of the aptasensor was prepared by depositing gold nanoparticles (AuNPs) on 3D graphene-modified electrode. The lysozyme binding aptamer (LBA) was attached to the 3D graphene/AuNPs electrode through gold-thiol affinity, hybridized with a complementary single-strand DNA (CDNA) of the lysozyme aptamer labeled by RuSiNPs@PLL-Au as an electrochemiluminescence intensity amplifier. Thanks to the synergistic amplification of the 3D graphene, the AuNPs and RuSiNPs@PLL-Au NPs linked to Ru(bpy)32+-ECL further enhanced the ECL intensity of the aptasensor. In presence of lysozyme, the CDNA segment of the self-assembled duplex was displaced by the lysozyme, resulting in decreased electrochemiluminescence signal. Under the optimized conditions, the decrease in electrochemiluminescence intensity varied proportionally with the logarithmic concentration of the lysozyme from 2.25 × 10-12 to 5.0 × 10-8 mol L-1, and the detection limit was estimated to 7.5 × 10-13 mol L-1. The aptasensor was further tested in real samples and found reliable for the detection of lysozyme, thus holding great potential application in food safety researches and bioassay analysis.