Abstract: Double-stranded RNA (dsRNA) induces sequence-specific post-transcriptional gene silencing in many organisms by a process known as RNA interference (RNAi). Using a Drosophila in vitro system, we demonstrate that 19-23 nt short RNA fragments are the sequence-specific mediators of RNAi. The short interfering RNAs (siRNAs) are generated by an RNase III-like processing reaction from long dsRNA. Chemically synthesized siRNA duplexes with overhanging 3′ ends mediate efficient target RNA cleavage in the lysate, and the cleavage site is located near the center of the region spanned by the guiding siRNA. Furthermore, we provide evidence that the direction of dsRNA processing determines whether sense or antisense target RNA can be cleaved by the produced siRNP complex.

Abstract: A method is provided for analyzing analyte ions in a liquid using a spectrometer incorporating an ion trap, using a capillary nozzle adjacent an inlet aperture for the ion trap. The liquid is electrosprayed from the capillary nozzle by generating an electric field at the nozzle to ionise the said analyte and produce a beam of charged spray particles, and the beam of charged particles is injected into the ion trap through the inlet aperture. The pressure within the capillary is such that flow of the liquid through the capillary occurs only in the presence of the said electric field, and flow of ions into the ion trap is controlled by varying the electric field.

Abstract: A method of electrospraying and thereby ionizing an analyte present in a liquid, using a capillary nozzle, in which an electric field is generated at the nozzle to ionise the analyte and produce a divergent beam of charged spray particles. The pressure within the capillary is such that flow of the liquid through the capillary occurs only in the presence of the electric field.