[Ru(phen)2DPPZ]2+ is in contact with DNA bases when it forms a luminescent complex with single-stranded oligonucleotides.
The luminescence intensity of the Delta- and Lambda-enantiomer of [Ru(phen)2DPPZ]2+ ([Ru(phenanthroline)2 dipyrido[3,2-a:2',3'-c]phenazine]2+) complex enhanced upon binding to double stranded DNA, which has been known as "light switch effect". The enhancement of the luminescence required the intercalation of the large ligand between DNA base pairs. In this study, we report the enhancement in the luminescence intensity when the metal complexes bind to single stranded oligonucleotides, indicating that the "light switch effect" does not require intercalation of the large DPPZ ligand. Oligonucleotides may provide a hydrophobic cavity for the [Ru(phen)2DPPZ]2+ complex to prevent the quenching by the water molecule. In the cavity, the metal complex is in contact with DNA bases as is evidenced by the observation that the excited energy of the DNA bases transfer to the bound metal complex. However, the contact of the metal complex with DNA bases is different from the stacking of DPPZ in the intercalation pocket. In addition to the normal two luminescence lifetimes, a short lifetime in the range of 1-2 ns was found for both the delta- and lambda-enantiomer of [Ru(phen)2DPPZ]2+ when complexed with single stranded oligonucleotides, which may be assigned to the metal complex that is outside of the cavity, interacting with phosphate groups of DNA.
Moon
Seok Joon
SJ
Department of Chemistry, Yeungnam University, Dae-dong, Kyoungsan City, Kyoung-buk 712-749, Republic of Korea.
Kim
Jong Moon
JM
Choi
Ji Youn
JY
Kim
Seog K
SK
Lee
Je Seung
JS
Jang
Ho G
HG
D001483:Base Sequence; D004247:DNA / Q000737:chemistry; D004277:DNA, Single-Stranded / Q000737:chemistry* / Q000378:metabolism; D049408:Luminescent Agents / Q000737:chemistry*; D008163:Luminescent Measurements; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000737:chemistry* / Q000378:metabolism; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism; D013237:Stereoisomerism
D004277:DNA, Single-Stranded; D049408:Luminescent Agents; D009841:Oligonucleotides; D009942:Organometallic Compounds; C466600:Ru(phen)(2)dipyrido(3,2-a-2',3'-c)phenazine; D004247:DNA