Label-free SERS strategy for rapid detection of capsaicin for identification of waste oils.

Identification of waste oils is challenging in the field of food safety due to the lack of common markers and straightforward analytical methods. Herein, we developed a novel label-free surface-enhanced Raman spectroscopy (SERS) strategy to identify waste oils using Ag nanoparticles solution (Ag NPs sol.) as a SERS substrate to significantly enhance the Raman signal of capsaicin marker molecule usually contained in the waste oils. The enhanced signal was directly detected by a portable Raman spectrometer with the limit of detection (LOD) of 2.9 µg L-1 within 10 min. Concentration-dependent SERS investigation showed the linear relationship between the SERS signal intensity of the characteristic peaks and the concentrations of capsaicin in the range of 10-2500 µg L-1 and the correlation coefficient was 0.9895. Our findings show the sensitivity, accessibility, and reliability of this method for the rapid identification of waste oils and furthermore for the practical applications in the field of food safety.

l-Phenylalanine Alters the Privileged Secondary Metabolite Production in the Marine-Derived Fungus Trichoderma erinaceum F1-1.

The effects of a single-amino-acid culture strategy on secondary metabolite production in the marine-derived fungus Trichoderma erinaceum F1-1 were investigated by culturing the fungus in GPY medium supplemented or not supplemented with l-phenylalanine. A suite of secondary metabolites, including seven terpenoids (1-7) and one polyketide (8), among which are four new compounds, harziandione A (1), cyclonerodiols A and B (3, 4), and trichodermaerin A (6), were isolated from the GPY medium without l-phenylanine, whereas 18 aromatic compounds (9-26), including six new compounds, trichoderolides A-F (9, 10, and 14-17), were isolated from the culture grown in the GPY medium with l-phenylalanine. The structures of the new compounds were determined by high-resolution mass spectrometry, NMR spectroscopic analysis, optical rotation calculations, chemical methods, and X-ray crystallography. Compounds 10, 12, 13, and 26 exhibited cytotoxic activities against MDA-MB-435 human melanocyte cancer cells. Compound 26 was cytotoxic to A549 adenocarcinomic human alveolar basal epithelial cells.

A potent Cas9-derived gene activator for plant and mammalian cells.

Overexpression of complementary DNA represents the most commonly used gain-of-function approach for interrogating gene functions and for manipulating biological traits. However, this approach is challenging and inefficient for multigene expression due to increased labour for cloning, limited vector capacity, requirement of multiple promoters and terminators, and variable transgene expression levels. Synthetic transcriptional activators provide a promising alternative strategy for gene activation by tethering an autonomous transcription activation domain (TAD) to an intended gene promoter at the endogenous genomic locus through a programmable DNA-binding module. Among the known custom DNA-binding modules, the nuclease-dead Streptococcus pyogenes Cas9 (dCas9) protein, which recognizes a specific DNA target through base pairing between a synthetic guide RNA and DNA, outperforms zinc-finger proteins and transcription activator-like effectors, both of which target through protein-DNA interactions 1 . Recently, three potent dCas9-based transcriptional activation systems, namely VPR, SAM and SunTag, have been developed for animal cells 2-6 . However, an efficient dCas9-based transcriptional activation platform is still lacking for plant cells 7-9 . Here, we developed a new potent dCas9-TAD, named dCas9-TV, through plant cell-based screens. dCas9-TV confers far stronger transcriptional activation of single or multiple target genes than the routinely used dCas9-VP64 activator in both plant and mammalian cells.

Shell-isolated nanoparticle-enhanced Raman spectroscopy.

Surface-enhanced Raman scattering (SERS) is a powerful spectroscopy technique that can provide non-destructive and ultra-sensitive characterization down to single molecular level, comparable to single-molecule fluorescence spectroscopy. However, generally substrates based on metals such as Ag, Au and Cu, either with roughened surfaces or in the form of nanoparticles, are required to realise a substantial SERS effect, and this has severely limited the breadth of practical applications of SERS. A number of approaches have extended the technique to non-traditional substrates, most notably tip-enhanced Raman spectroscopy (TERS) where the probed substance (molecule or material surface) can be on a generic substrate and where a nanoscale gold tip above the substrate acts as the Raman signal amplifier. The drawback is that the total Raman scattering signal from the tip area is rather weak, thus limiting TERS studies to molecules with large Raman cross-sections. Here, we report an approach, which we name shell-isolated nanoparticle-enhanced Raman spectroscopy, in which the Raman signal amplification is provided by gold nanoparticles with an ultrathin silica or alumina shell. A monolayer of such nanoparticles is spread as 'smart dust' over the surface that is to be probed. The ultrathin coating keeps the nanoparticles from agglomerating, separates them from direct contact with the probed material and allows the nanoparticles to conform to different contours of substrates. High-quality Raman spectra were obtained on various molecules adsorbed at Pt and Au single-crystal surfaces and from Si surfaces with hydrogen monolayers. These measurements and our studies on yeast cells and citrus fruits with pesticide residues illustrate that our method significantly expands the flexibility of SERS for useful applications in the materials and life sciences, as well as for the inspection of food safety, drugs, explosives and environment pollutants.