DNA-mediated charge transport requires conformational motion of the DNA bases: elimination of charge transport in rigid glasses at 77 K.
Identifieur interne : 003102 ( Main/Merge ); précédent : 003101; suivant : 003103DNA-mediated charge transport requires conformational motion of the DNA bases: elimination of charge transport in rigid glasses at 77 K.
Auteurs : Melanie A. O'Neill [États-Unis] ; Jacqueline K. BartonSource :
- Journal of the American Chemical Society [ 0002-7863 ] ; 2004.
Descripteurs français
- KwdFr :
- MESH :
English descriptors
- KwdEn :
- MESH :
- chemical , chemistry : 2-Aminopurine, DNA.
- Cold Temperature, Fluorescence Polarization, Nucleic Acid Conformation, Spectrometry, Fluorescence.
Abstract
We have proposed that DNA-mediated charge transport (CT) is gated by base motions, with only certain base conformations being CT-active; a CT-active conformation can be described as a domain, a transiently extended pi-orbital defined dynamically by DNA sequence. Here, to explore these CT-active conformations, we examine the yield of base-base CT between photoexcited 2-aminopurine (Ap*) and guanine in DNA in rigid LiCl glasses at 77 K, where conformational rearrangement is effectively eliminated. Duplex DNA assemblies (35-mers) were constructed containing adenine bridges Ap(A)nG (n = 0-4). The yield of CT was monitored through fluorescence quenching of Ap* by G. We find, first, that the emission intensity of Ap* in all DNA duplexes increases dramatically upon cooling and becomes comparable to free Ap*. This indicates that all quenching of Ap* in duplex DNA is a dynamic process that requires conformational motion of the DNA bases. Second, DNA-mediated CT between Ap* and G is not observed at 77 K; rather than hindering the ability of DNA to transport charge, conformational motion is required. Moreover, the lack of DNA-mediated CT at 77 K, even through the shortest bridge, suggests that the static structures adopted upon cooling do not represent optimum CT-active conformations. These observations are consistent with our model of conformationally gated CT. Through conformational motion of the DNA bases, CT-active domains form and break-up transiently, both facilitating and limiting CT.
DOI: 10.1021/ja0455897
PubMed: 15479072
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pubmed:15479072Le document en format XML
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O'Neill</name><affiliation wicri:level="1"><nlm:affiliation>Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.</nlm:affiliation><country xml:lang="fr">États-Unis</country><wicri:regionArea>Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125</wicri:regionArea><wicri:noRegion>California 91125</wicri:noRegion></affiliation></author><author><name sortKey="Barton, Jacqueline K" sort="Barton, Jacqueline K" uniqKey="Barton J" first="Jacqueline K" last="Barton">Jacqueline K. Barton</name></author></analytic><series><title level="j">Journal of the American Chemical Society</title><idno type="ISSN">0002-7863</idno><imprint><date when="2004" type="published">2004</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>2-Aminopurine (chemistry)</term><term>Cold Temperature</term><term>DNA (chemistry)</term><term>Fluorescence Polarization</term><term>Nucleic Acid Conformation</term><term>Spectrometry, Fluorescence</term></keywords><keywords scheme="KwdFr" xml:lang="fr"><term>ADN ()</term><term>Amino-2 purine ()</term><term>Basse température</term><term>Conformation d'acide nucléique</term><term>Polarisation de fluorescence</term><term>Spectrométrie de fluorescence</term></keywords><keywords scheme="MESH" type="chemical" qualifier="chemistry" xml:lang="en"><term>2-Aminopurine</term><term>DNA</term></keywords><keywords scheme="MESH" xml:lang="en"><term>Cold Temperature</term><term>Fluorescence Polarization</term><term>Nucleic Acid Conformation</term><term>Spectrometry, Fluorescence</term></keywords><keywords scheme="MESH" xml:lang="fr"><term>ADN</term><term>Amino-2 purine</term><term>Basse température</term><term>Conformation d'acide nucléique</term><term>Polarisation de fluorescence</term><term>Spectrométrie de fluorescence</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">We have proposed that DNA-mediated charge transport (CT) is gated by base motions, with only certain base conformations being CT-active; a CT-active conformation can be described as a domain, a transiently extended pi-orbital defined dynamically by DNA sequence. Here, to explore these CT-active conformations, we examine the yield of base-base CT between photoexcited 2-aminopurine (Ap*) and guanine in DNA in rigid LiCl glasses at 77 K, where conformational rearrangement is effectively eliminated. Duplex DNA assemblies (35-mers) were constructed containing adenine bridges Ap(A)nG (n = 0-4). The yield of CT was monitored through fluorescence quenching of Ap* by G. We find, first, that the emission intensity of Ap* in all DNA duplexes increases dramatically upon cooling and becomes comparable to free Ap*. This indicates that all quenching of Ap* in duplex DNA is a dynamic process that requires conformational motion of the DNA bases. Second, DNA-mediated CT between Ap* and G is not observed at 77 K; rather than hindering the ability of DNA to transport charge, conformational motion is required. Moreover, the lack of DNA-mediated CT at 77 K, even through the shortest bridge, suggests that the static structures adopted upon cooling do not represent optimum CT-active conformations. These observations are consistent with our model of conformationally gated CT. Through conformational motion of the DNA bases, CT-active domains form and break-up transiently, both facilitating and limiting CT.</div></front></TEI></record>Pour manipuler ce document sous Unix (Dilib)
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