Bulletin of the American Physical Society
Spring 2012 Meeting of the APS Ohio-Region Section
Volume 57, Number 4
Friday–Saturday, April 13–14, 2012; Columbus, Ohio
Session H1: Biophysics Invited Session II |
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Chair: Ralf Bundschuh, Ohio State University Room: Alpheus Smith Laboratory 1153 |
Saturday, April 14, 2012 10:15AM - 11:15AM |
H1.00001: Single-stranded DNA scanning and deamination with Single molecule resolution Invited Speaker: David Rueda Over the past decade, single-molecule fluorescence resonance energy transfer spectroscopy (smFRET) has become an increasingly popular tool to study the structural dynamics of biopolymers, such as DNA, RNA and proteins. The most attractive aspect of single-molecule experiments is that, unlike ensemble-averaged techniques, they directly reveal the structural dynamics of individual molecules, which would otherwise be hidden in ensemble-averaged experiments. Here, we will present a novel single molecule assay to study, for the first time, scanning of an enzyme (APOBEC3G, involved in the defense against HIV) on single stranded DNA (ssDNA). We have investigated the ssDNA scanning and activity of Apo3G with smFRET. Our data show that Apo3G scans ssDNA randomly and bidirectionally with average excursion lengths of $\sim$ 10 $\AA$ and $\sim$1 s-1 scanning rates. Apo3G quasi-localization is observed on highly reactive motifs located near the one end of the ssDNA. Motif-dependent ssDNA bending is also observed, where the bending is maximal for highly reactive targets located near the DNA end. Interestingly, both the Apo3G scanning and Apo3G-induced ssDNA bending is reduced with lowered ionic strength, indicating that Apo3G motion on ssDNA is facilitated by salt by reducing `electrostatic friction'. Although scanning is random, asymmetric catalytic orientation may be the reason for Apo3G directional activity. [Preview Abstract] |
Saturday, April 14, 2012 11:15AM - 12:15PM |
H1.00002: The Mechanics of the Human Genome Invited Speaker: Michael Poirier Each of our cells contains 1 meter of DNA that is tightly wrapped to fit inside the $\sim$5 $\mu$ wide nucleus of the cell. This highly condensed state of our DNA plays a central role in how the information in our genes is replicated, read and repaired. Yet, the mechanics by which the genome organization regulates the processing of DNA remains a mystery. I will discuss what is currently understood about the first level of genomic organization, the nucleosome - a 50 nm stretch of DNA tightly wrapped $\sim$2 times around a protein core. Recent measurements from our group suggest how mechanical properties of our genome could regulate gene expression and DNA repair. [Preview Abstract] |
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