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<p class="MsoNormal"><span style="font-size:14.0pt">There will be a Modern Optics and Spectroscopy Seminar held next
<b>Tuesday, March 13 at 12pm </b>in <b><span style="color:red">NE47-189 </span></b></span><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:14.0pt;color:red"> </span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:14.0pt;color:red">**Please note location**</span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:14.0pt"> </span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:14.0pt">Andrew H. Marcus</span></b><o:p></o:p></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">University of Oregon</span></i><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:14.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><b><i><span style="font-size:14.0pt">“Spectroscopic studies of exciton-coupled cyanine dimers (Cy3)2 in double-stranded DNA”<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:14.0pt"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">Understanding the properties of electronically interacting molecular chromophores,<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">which involve internally coupled electronic-vibrational motions, is important to the spectroscopy<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">of many biologically relevant systems. We apply linear absorption, circular dichroism (CD),<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">and two-dimensional fluorescence spectroscopy (2DFS) to study the polarized collective<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">excitations of excitonically coupled cyanine dimers (Cy3)2 that are rigidly positioned within the<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">opposing sugar-phosphate backbones of the double-stranded region of a double-stranded (ss) –<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">single-stranded (ss) DNA fork construct. We show that the exciton-coupling strength of the<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">(Cy3)2-DNA construct can be systematically varied with temperature below the ds – ss DNA<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">denaturation transition. We interpret spectroscopic measurements in terms of the Holstein<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">vibronic dimer model, from which we obtain information about the local conformation of the<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">(Cy3)2 dimer, as well as the degree of static disorder experienced by the Cy3 monomer and the<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">(Cy3)2 dimer probe locally within their respective DNA duplex environments. The properties of<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">the (Cy3)2-DNA construct we determine suggest that it may be employed as a useful model<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">system to test fundamental concepts of protein-DNA interactions, and the role of electronic-vibrational<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">coherence in electronic energy migration within exciton-coupled bio-molecular<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">arrays.<o:p></o:p></span></i></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><br>
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</span><o:p></o:p></p>
<p class="MsoNormal">Refreshments will be served immediately following the seminar<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt">Christine Brooks</span></b><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Administrative Assistant</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Massachusetts Institute of Technology</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Department of Chemistry</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">77 Massachusetts Ave, 6-333</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Cambridge, MA 02139</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">p: 617.253.7239</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">e: <a href="mailto:cbrooks@mit.edu">cbrooks@mit.edu</a></span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
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