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Article: Femtosecond time- and wavelength-resolved fluorescence and absorption spectroscopic study of the excited states of adenosine and an adenine oligomer

TitleFemtosecond time- and wavelength-resolved fluorescence and absorption spectroscopic study of the excited states of adenosine and an adenine oligomer
Authors
Issue Date2006
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.html
Citation
Journal Of The American Chemical Society, 2006, v. 128 n. 36, p. 11894-11905 How to Cite?
AbstractBy employing broadband femtosecond Kerr-gated time-resolved fluorescence (KTRF) and transient absorption (TA) techniques, we report the first (to our knowledge) femtosecond combined time- and wavelength-resolved study on an ultraviolet-excited nucleoside and a single-stranded oligonucleotide (namely adenosine (Ado) and single-stranded adenine oligomer (dA)20) in aqueous solution. With the advantages of the ultrafast time resolution, the broad spectral and temporal probe window, and a high sensitivity, our KTRF and TA results enable the real time monitoring and spectral characterization of the excited-state relaxation processes of the Ado nucleoside and (dA)20 oligonucleotide investigated. The temporal evolution of the 267 nm excited Ado KTRF spectra indicates there are two emitting components with lifetimes of ∼0.13 ps and ∼0.45 ps associated with the La and L b ππ* excited states, respectively. These Ado results reveal no obvious evidence for the involvement of the nπ* state along the irradiative internal conversion pathway. A distinct mechanism involving only the two ππ* states has been proposed for the ultrafast Ado deactivation dynamics in aqueous solution. The time dependence of the 267 nm excited (dA)20 KTRF and TA spectra reveals temporal evolution from an ultrafast "A-like" state (with a ∼0.39 ps decay time) to a relatively long-lived E1 "excimer" (∼4.3 ps decay time) and an E2 "excimer-like" (∼182 ps decay time) state. The "A-like" state has a spectral character closely resembling the excited state of Ado. Comparison of the spectral evolution between the results for Ado and (dA)20 provides unequivocal evidence for the local excitation character of the initially photoexcited (dA)20. The rapid transformation of the locally excited (dA)20 component into the delocalized E1 "excimer" state which then further evolves into the E2 "excimer-like" state indicates that base stacking has a high ability to modify the excited-state deactivation pathway. This modification appears to occur by suppressing the internal conversion pathway of an individually excited base component where the stacking interaction mediates efficient interbase energy transfer and promotes formation of the collective excited states. This feature of the local excitation that is subsequently followed by rapid energy delocalization into nearby bases may occur in many base multimer systems. Our results provide an important new contribution to better understanding DNA photophysics. © 2006 American Chemical Society.
Persistent Identifierhttp://hdl.handle.net/10722/70271
ISSN
2015 Impact Factor: 13.038
2015 SCImago Journal Rankings: 7.123
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorKwok, WMen_HK
dc.contributor.authorMa, Cen_HK
dc.contributor.authorPhillips, DLen_HK
dc.date.accessioned2010-09-06T06:21:19Z-
dc.date.available2010-09-06T06:21:19Z-
dc.date.issued2006en_HK
dc.identifier.citationJournal Of The American Chemical Society, 2006, v. 128 n. 36, p. 11894-11905en_HK
dc.identifier.issn0002-7863en_HK
dc.identifier.urihttp://hdl.handle.net/10722/70271-
dc.description.abstractBy employing broadband femtosecond Kerr-gated time-resolved fluorescence (KTRF) and transient absorption (TA) techniques, we report the first (to our knowledge) femtosecond combined time- and wavelength-resolved study on an ultraviolet-excited nucleoside and a single-stranded oligonucleotide (namely adenosine (Ado) and single-stranded adenine oligomer (dA)20) in aqueous solution. With the advantages of the ultrafast time resolution, the broad spectral and temporal probe window, and a high sensitivity, our KTRF and TA results enable the real time monitoring and spectral characterization of the excited-state relaxation processes of the Ado nucleoside and (dA)20 oligonucleotide investigated. The temporal evolution of the 267 nm excited Ado KTRF spectra indicates there are two emitting components with lifetimes of ∼0.13 ps and ∼0.45 ps associated with the La and L b ππ* excited states, respectively. These Ado results reveal no obvious evidence for the involvement of the nπ* state along the irradiative internal conversion pathway. A distinct mechanism involving only the two ππ* states has been proposed for the ultrafast Ado deactivation dynamics in aqueous solution. The time dependence of the 267 nm excited (dA)20 KTRF and TA spectra reveals temporal evolution from an ultrafast "A-like" state (with a ∼0.39 ps decay time) to a relatively long-lived E1 "excimer" (∼4.3 ps decay time) and an E2 "excimer-like" (∼182 ps decay time) state. The "A-like" state has a spectral character closely resembling the excited state of Ado. Comparison of the spectral evolution between the results for Ado and (dA)20 provides unequivocal evidence for the local excitation character of the initially photoexcited (dA)20. The rapid transformation of the locally excited (dA)20 component into the delocalized E1 "excimer" state which then further evolves into the E2 "excimer-like" state indicates that base stacking has a high ability to modify the excited-state deactivation pathway. This modification appears to occur by suppressing the internal conversion pathway of an individually excited base component where the stacking interaction mediates efficient interbase energy transfer and promotes formation of the collective excited states. This feature of the local excitation that is subsequently followed by rapid energy delocalization into nearby bases may occur in many base multimer systems. Our results provide an important new contribution to better understanding DNA photophysics. © 2006 American Chemical Society.en_HK
dc.languageengen_HK
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.htmlen_HK
dc.relation.ispartofJournal of the American Chemical Societyen_HK
dc.titleFemtosecond time- and wavelength-resolved fluorescence and absorption spectroscopic study of the excited states of adenosine and an adenine oligomeren_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0002-7863&volume=128&spage=11894&epage=11905&date=2006&atitle=Femtosecond+Time-+and+Wavelength-Resolved+Fluorescence+and+Absorption+Spectroscopic+Study+of+the+Excited+States+of+Adenosine+and+an+Adenine+Oligomer+en_HK
dc.identifier.emailMa, C:macs@hkucc.hku.hken_HK
dc.identifier.emailPhillips, DL:phillips@hku.hken_HK
dc.identifier.authorityMa, C=rp00758en_HK
dc.identifier.authorityPhillips, DL=rp00770en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1021/ja0622002en_HK
dc.identifier.pmid16953630-
dc.identifier.scopuseid_2-s2.0-33748493389en_HK
dc.identifier.hkuros131822en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-33748493389&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume128en_HK
dc.identifier.issue36en_HK
dc.identifier.spage11894en_HK
dc.identifier.epage11905en_HK
dc.identifier.isiWOS:000240291900039-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridKwok, WM=7103129332en_HK
dc.identifier.scopusauthoridMa, C=7402924979en_HK
dc.identifier.scopusauthoridPhillips, DL=7404519365en_HK

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