INVESTIGATING NOVEL DNA FLUORSCENCE LABELING PROBES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. K. Burgess and co-workers have developed several different types of fluorescence probes for DNA labeling containing more than one fluorescent chromophore, which have distinct visible fluorescence spectra and yet have the same high absorption cross sections at a common wavelength. Two types of such molecules have included trial systems involving oligonucleotides with strongly fluorescent groups conjugated to a nucleobase such as thymidine, and rigid, conjugated, fluoresceinated thymidine triphosphates incorporated into DNA. The aim of the current project is to directly measure energy transfer dynamics by two distinct methods: fluorescence upconversion (150 fs resolution) and a two-photon induced fluorescence technique (~100 fs resolution). Recent comparisons with other dual chromophore probes, involving derivatives of rhodamine and fluorescein, have revealed a correlation of the energy transfer rate with the relative orientation of the electronic transition moments of the two chromophores and the axis of the unsaturated group connecting them. These correlations are currently being examined, through studies of both the energy transfer rate and the fluorescence anisotropy of each type of chromophore pair.