43 research outputs found
RNA Polymerase Alters the Mobility of an A-Residue Crucial to Polymerase-Induced Melting of Promoter DNA †
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Progress in the development and production of nanoscale iron-coating catalysts
At the Pacific Northwest Laboratory (PNL) we have undertaken a program to investigate nanocrystalline ion-based powders as catalytic precursors in a variety of hydrocracking reactions, including coal liquefaction. One ultrafine powder synthesis method developed at PNL, the Rapid of precursors in Solution (RTDS) process, appears to be particularly large scale production of nanocrystalline powders. Using model compounds we have demonstrated that iron-based RTDS powders can be used to produce highly active carbon-carbon bond scission catalysts under reaction conditions relevant to coal liquefaction processes. In this paper we present recent results of attempts at modifying the activity of RTDS-generated iron-based catalyst powders by doping with other metals and the results of scaleup efforts to produce kilogram quantities of active catalyst precursor by this process
Verification and Biophysical Characterization of a New Three-Color Förster Resonance-Energy-Transfer (FRET) System in DNA
Single-Molecule Three-Color FRET
Fluorescence resonance energy transfer (FRET) measured at the single-molecule level can reveal conformational changes of biomolecules and intermolecular interactions in physiologically relevant conditions. Thus far single-molecule FRET has been measured only between two fluorophores. However, for many complex systems, the ability to observe changes in more than one distance is desired and FRET measured between three spectrally distinct fluorophores can provide a more complete picture. We have extended the single-molecule FRET technique to three colors, using the DNA four-way (Holliday) junction as a model system that undergoes two-state conformational fluctuations. By labeling three arms of the junction with Cy3 (donor), Cy5 (acceptor 1), and Cy5.5 (acceptor 2), distance changes between the donor and acceptor 1, and between the donor and acceptor 2, can be measured simultaneously. Thus we are able to show that the acceptor 1 arm moves away from the donor arm at the same time as the acceptor 2 arm approaches the donor arm, and vice versa, marking the first example of observing correlated movements of two different segments of a single molecule. Our data further suggest that Holliday junction does not spend measurable time with any of the helices unstacked, and that the parallel conformations are not populated to a detectable degree