TbMP42 is a structure-sensitive ribonuclease that likely follows a metal ion catalysis mechanism

RNA editing in African trypanosomes is characterized by a uridylate-specific insertion and/or deletion reaction that generates functional mitochondrial transcripts. The process is catalyzed by a multi-enzyme complex, the editosome, which consists of approximately 20 proteins. While for some of the polypeptides a contribution to the editing reaction can be deduced from their domain structure, the involvement of other proteins remains elusive. TbMP42, is a component of the editosome that is characterized by two C2H2-type zinc-finger domains and a putative oligosaccharide/oligonucleotide-binding fold. Recombinant TbMP42 has been shown to possess endo/exoribonuclease activity in vitro; however, the protein lacks canonical nuclease motifs. Using a set of synthetic gRNA/pre-mRNA substrate RNAs, we demonstrate that TbMP42 acts as a topology-dependent ribonuclease that is sensitive to base stacking. We further show that the chelation of Zn2+ cations is inhibitory to the enzyme activity and that the chemical modification of amino acids known to coordinate Zn2+ inactivates rTbMP42. Together, the data are suggestive of a Zn2+-dependent metal ion catalysis mechanism for the ribonucleolytic activity of rTbMP42

Analysis of the initial performance of the ATLAS Level-1 Calorimeter Trigger

The ATLAS first-level calorimeter trigger is a hardware-based system designed to identify high-pT jets, electron/photon and tau candidates and to measure total and missing ET in the calorimeters. The installation of the full system of custom modules, crates and cables was completed in late 2007, but, even before the completion, it was being used as a trigger during ATLAS commissioning and integration. During 2008, the performance of the full system has been tuned during further commissioning and cosmic runs, leading to its use in initial LHC data taking. Results and analysis of the trigger performance in these runs will be presented

Control, Test and Monitoring Software Framework for the ATLAS Level-1 Calorimeter Trigger

The ATLAS first-level calorimeter trigger is a hardware-based system designed to identify high-pT jets, electron/photon and tau candidates and to measure total and missing ET in the ATLAS calorimeters. The complete trigger system consists of over 300 customdesignedVME modules of varying complexity. These modules are based around FPGAs or ASICs with many configurable parameters, both to initialize the system with correct calibrations and timings and to allow flexibility in the trigger algorithms. The control, testing and monitoring of these modules requires a comprehensive, but well-designed and modular, software framework, which we will describe in this paper

Digital signal integrity and stability in the ATLAS Level-1 Calorimeter Trigger

The ATLAS Level-1 calorimeter trigger is a hardware-based system with the goal of identifying high-pT objects and to measure total and missing ET in the ATLAS calorimeters within an overall latency of 2.5 microseconds. This trigger system is composed of the Preprocessor which digitises about 7200 analogue input channels and two digital processors to identify high-pT signatures and to calculate the energy sums. The digital part consists of multi-stage, pipelined custom-built modules. The high demands on connectivity between the initial analogue stage and digital part and between the custom-built modules are presented. Furthermore the techniques to establish timing regimes and verify connectivity and stable operation of these digital links will be described

Testing and calibrating analogue inputs to the ATLAS Level-1 Calorimeter Trigger

The ATLAS Level-1 Calorimeter Trigger is a hardwarebased system which aims to identify objects with high transverse momentum within an overall latency of 2.5 μs. It is composed of a PreProcessor system (PPr) which digitises 7200 analogue input channels, determines the bunch crossing of the interaction, applies a digital noise filter, and provides a fine calibration; and two subsequent digital processors. The PreProcessor system needs various channel dependent parameters to be set in order to provide digital signals which are aligned in time and have proper energy calibration. The different techniques which are used to derive these parameters are described along with the quality tests of the analogue input signals