Water-soluble photoluminescent d-mannose and l-alanine functionalized silicon nanocrystals and their application to cancer cell imaging.

Herein, we report the straightforward synthesis, photoluminescent properties, and cell imaging studies of d-mannose and l-alanine functionalized silicon nanocrystals (SiNCs). Tailoring nanocrystal surface functionalization is essential to interfacing SiNCs with their environment and rendering them stable - surface modification also offers the opportunity to target specific cell types for imaging. A simple and versatile surface modification procedure was developed to tether biomolecules onto the SiNC surfaces and render them water-soluble. The presented approach is precious metal-catalyst free, straightforward, and provides carbohydrate and amino acid functionalized SiNCs. The functionalized SiNCs have been investigated by fluorescence microscopy and our results indicate that they can be internalized by MCF-7 human breast cancer cells as shown in the cell imaging studies. The obtained SiNCs were characterized using FTIR, XPS, PL, and TEM.

Synthesis of nitrogen-containing furanose sugar nucleotides for use as enzymatic probes.

The sugar nucleotides UDP-2-acetamido-2-deoxy-α-D-galactofuranose (UDP-GalfNAc) and UDP-2-azido-2-deoxy-α-D-galactofuranose (UDP-GalfN3) have been synthesized in preparative scale for the first time. These compounds are useful probes for studying the biosynthesis of glycans containing galactofuranose and/or 2-acetamido-2-deoxy-α-D-galactofuranose residues.

Detoxification of cruciferous phytoalexins in Botrytis cinerea: spontaneous dimerization of a camalexin metabolite.

Phytopathogenic fungi are able to overcome plant chemical defenses through detoxification reactions that are enzyme mediated. As a result of such detoxifications, the plant is quickly depleted of its most important antifungal metabolites and can succumb to pathogen attack. Understanding and predicting such detoxification pathways utilized by phytopathogenic fungi could lead to approaches to control plant pathogens. Towards this end, the inhibitory activities and metabolism of the cruciferous phytoalexins camalexin, brassinin, cyclobrassinin, and brassilexin by the phytopathogenic fungus Botrytis cinerea Pers. (teleomorph: Botryotinia fuckeliana) was investigated. Brassilexin was the most antifungal of the phytoalexins, followed by camalexin, cyclobrassinin and brassinin. Although B. cinerea is a species phylogenetically related to the phytopathogenic fungus Sclerotinia sclerotiorum (Lib) de Bary, contrary to S. sclerotiorum, detoxification of strongly antifungal phytoalexins occurred via either oxidative degradation or hydrolysis but not through glucosylation, suggesting that glucosyl transferases are not involved. A strongly antifungal bisindolylthiadiazole that B. cinerea could not detoxify was discovered, which resulted from spontaneous oxidative dimerization of 3-indolethiocarboxamide, a camalexin detoxification product.

Impact of cruciferous phytoalexins on the detoxification of brassilexin by the blackleg fungus pathogenic to brown mustard.

The biotransformation of brassilexin, a potent phytoalexin produced by brown mustard (Brassica juncea L.), in the presence of various cruciferous phytoalexins was investigated. An important group of isolates of the fungal species Leptosphaeria maculans (Laird 2 and Mayfair 2), which is virulent to brown mustard, but not to canola, was used in this investigation. Brassilexin was detoxified by the fungus, but none of the phytoalexins seemed to affect substantially the rate of brassilexin detoxification; after 12 h of incubation, the amounts of brassilexin remaining in culture were as low as in controls, except in co-incubations with cyclobrassinin and sinalexin, which afforded intermediates that in solution oxidized spontaneously to brassilexin.