EXCITED STATE DYNAMICS OF DNA BASE PAIRS

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In this award, funded by the Experimental Physical Chemistry Program of the Division of Chemistry, Professor Mattanjah S. de Vries of the University of California Santa Barbara, together with his undergraduate, graduate and high school student researchers, will investigate the photochemistry and in particular the excited state dynamics of isolated nucleobases and their clusters with each other and with water. Following absorption of UV light, DNA bases can avoid chemical transformation by very rapidly diffusing the excitation energy to heat, in a process called internal conversion, which can safely be transferred to the environment. Thus a short lived excited state provides photochemical stability. This process strongly depends on molecular structure and is remarkably prevalent in the specific forms in which nucleobases occur in biological contexts. These short lived states have been difficult to study experimentally and therefore most evidence for these processes is still indirect. This project will employ novel gas phase techniques for these studies in collaboration with Professor Pavel Hobza in Prague, whose group will apply the newest computational modeling techniques for analysis. Professor de Vries will engage students in his efforts and contribute to the Bay Area Museum-School Online Science Learning Collaboratory Pilot Projec.How DNA responds to radiation is relevant to human health because radiation damage can affect genetic propagation and lead to cancer. DNA photochemistry is also important for our understanding of how life on earth developed, because prebiotic chemistry presumably occurred before formation of an oxygen rich atmosphere and thus under more energetic UV irradiation than what reaches the earth?s surface today. To understand this photochemistry in detail and at the molecular level we need to study it in isolated nucleobases and base pairs and compare the results with quantum chemical modeling. This approach allows Professor de Vries and his collaborators to observe intrinsic molecular properties and understand how those shape the bulk behavior of biological systems. Therefore, this research will contribute to the most basic understanding of fundamental processes that govern the molecular building blocks of life. These topics, in combination with cutting-edge laser and computational techniques, lend themselves extraordinary well to outreach activities, which this group traditionally undertakes. These activities include mentoring undergraduates, K-12 outreach activities, participation in the Bay Area Museum-School Online Science Learning Collaboratory Pilot Project, and collaboration with the students at Jackson State University, a historically black college in Mississippi.