The Raman spectra of single-walled carbon nanotubes (SWNTs) produced by the catalytic decomposition of hydrocarbons have been measured in the range of 100–7500 cm−1. The tangential C–C stretching modes show an unusual resonant enhancement process that results from the one-dimensional quantum confinement of the electrons in the SWNT, and its intensity of the tangential C–C stretching mode is about 100 times as strong as that of highly oriented pyrolytic graphite. Because of the resonant enhancement, high-order Raman bands up to fifth order have been revealed and assigned to the corresponding fundamentals.
The type III-E CRISPR–Cas systems are newly identified adaptive immune systems in prokaryotes that use a single Cas7–11 protein to specifically cleave target RNA. Cas7–11 could associate with Csx29, a putative caspase-like protein encoded by the gene frequently found in the type III-E loci, suggesting a functional linkage between the RNase and protease activities in type III-E systems. Here, we demonstrated that target RNA recognition would stimulate the proteolytic activity of Csx29, and protein Csx30 is the endogenous substrate. More interestingly, while the cognate target RNA recognition would activate Csx29, non-cognate target RNA with the complementary 3′ anti-tag sequence inhibits the enzymatic activity. Csx30 could bind to the sigma factor RpoE, which may initiate the stress response after proteolytic cleavage. Combined with biochemical and structural studies, we have elucidated the mechanisms underlying the target RNA-guided proteolytic activity of Csx29. Our work will guide further developments leveraging this simple RNA targeting system for RNA and protein-related applications.
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