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SCIENCE AT THE EDGE SEMINAR QB/GEDD Friday, February 25 at 11:30am Room 1400 Biomedical and Physical Sciences Bldg. Refreshments at 11:15 Hashim M. Al-Hashimi Department of Chemistry and Biophysics, University of Michigan The Nucleic Acid Dance at Atomic-Resolution NMR data and computational molecular dynamics simulations are combined to yield a 3D atomic view of thermal fluctuations in nucleic acids over timescales spanning picoseconds to milliseconds. Detailed analysis of RNA dynamic trajectories reveals spatially choreographed movements within a pre-confined space in which helices linked by two-way junctions twist in a synchronized manner while simultaneously bending. The spatial choreography of the dynamics is a universal and fundamental feature of RNA structure, which arises from topological constraints encoded at the secondary structure level. A combined NMR-computational analysis reveals that simple DNA duplexes undergo excursions outside the Watson-Crick framework towards Hoogsteen base pairs that are transiently (<1%) sampled ubiquitously across all CA steps at slow micro-to-millisecond timescales. The observation of Hoogsteen base pairs in duplex DNAs bound to proteins and in the context of damaged DNA suggest that DNA sequences code for excited-state structures that could provide yet another layer of genetic information. Helen Geiger Administrative Assistant Quantitative Biology Graduate Program/ Gene Expression in Development & Disease Michigan State University 502B Biochemistry Building East Lansing, MI 48824 Phone: (517) 432-9895 Fax: (517) 353-9334 E-mail: [log in to unmask]<mailto:[log in to unmask]> Web: http://qbmi.msu.edu<http://qbmi.msu.edu/> http://www.bch.msu.edu/GEDD/index.htm<http://www.bch.msu.edu/GEDD/MSU-TRSB-Symposium.htm>