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alpha-Synuclein (alpha-Syn) is an intrinsically disordered protein which self-assembles into highly organized beta-sheet structures that accumulate in plaques in brains of Parkinson's disease patients. Oxidative stress influences alpha-Syn structure and selfassembly; however, the basis for this remains unclear. Here we characterize the chemical and physical effects of mild oxidation on monomeric alpha-Syn and its aggregation. Using a combination of biophysical methods, small-angle X-ray scattering, and native ion mobility mass spectrometry, we find that oxidation leads to formation of intramolecular dityrosine cross-linkages and a compaction of the alpha-Syn monomer by a factor of root 2. Oxidation-induced compaction is shown to inhibit ordered self-assembly and amyloid formation by steric hindrance, suggesting an important role of mild oxidation in preventing amyloid formation.

Greater understanding of the mutual influence between DNA and the associated nanomaterial on the properties of each other can provide alternative strategies for designing and developing DNA nanomachines. DNA secondary structures are essential for encapsulating highly emissive silver nanoclusters (DNA/AgNCs). Likewise, AgNCs stabilize secondary DNA structures, such as hairpin DNA, duplex DNA, and parallel-motif DNA triplex. In this study, we found that the fluorescence of AgNCs encapsulated within a Hoogsteen triplex DNA structure can be turned on and off in response to pH changes. We also show that AgNCs can act as nanoscale rivets, linking two functionally distinctive DNA nanostructures. For instance, we found that a Hoogsteen triplex DNA structure with a seven-cytosine loop encapsulates red fluorescent AgNCs. The red fluorescence faded under alkaline conditions, whereas the fluorescence was restored in a near-neutral environment. Hairpin DNA and random DNA structures did not exhibit this pH-dependent AgNCs fluorescence. A fluorescence lifetime measurement and a small-angle X-ray scattering analysis showed that the triplex DNA-encapsulated AgNCs were photophysically convertible between bright and dark states. An in-gel electrophoresis analysis indicated that bright and dark convertibility depended on the AgNCs-riveted dimerization of the triplex DNAs. Moreover, we found that AgNCs rivet the triplex DNA and hairpin DNA to form a heterodimer, emitting orange fluorescence. Our findings suggest that AgNCs between two cytosine-rich loops can be used as nanorivets in designing noncanonical DNA origami beyond Watson-Crick base pairing.

Fungi have the potential to produce a wide range of secondary metabolites including polyketides and small peptides produced by nonribosomal peptide synthetases (NPS). Fusarium graminearum is a mycotoxin producing pathogen of cereals and knowledge of the infection process is essential for the development of disease control. Bioinformatics provide a means to identify genes encoding NPSs, the products of which may act as fungal virulence factors. The F. graminearum genome sequence was analysed and similarity searches and application of prediction server service identified 15 putative NPS genes. NPS1 and NPS2, were found to be related to genes involved in NPS hydroxamate siderophore biosynthesis and chemical analysis of a F. graminearum NPS2 deletion mutant showed that this gene encodes the NPS responsible for the biosynthesis of ferricrocin. The expression of the NPS genes was analysed in Fusarium culmorum. NPS1 and NPS19 differed from the remainder of the genes, as they were only expressed during infection of barley roots and not under the different culture conditions tested. Strains of F. graminearum, F. culmorum and Fusarium pseudograminearum were examined for the presence and expression of the 15 identified NPS genes. With the exception of NPS18, that is absent in F. pseudograminearum, all the NPS genes are represented in the diffferent species. Lack of transcripts from some genes and the presence of frameshift and stop codons in four of the NPS genes in the sequenced F. graminearum strain suggest that some are pseudogenes.