Using external field effects for elucidating specific features in dye–DNA interaction

Spectroscopy of proteins at low temperature. Part I: Experiments with molecular ensembles

“…In reality, however, things can be more complicated, for instance due to the fact that the state of protonation of the chromophore or its structure can change in the respective environment which would give rise to a change of Δ μ 0 . This could even depend on frequency within the inhomogeneous band leading to color effects in the Stark-splitting, as has been observed for dye labeled DNA-strands [69]. Apart from the fact that the observation of color effects can serve as an important tool to identify the major contributions to the chromophore-protein interaction, the possibility of high resolution frequency tuning brings about another big advantage: it is possible to select different conformations of a protein with different properties just by tuning the frequency.…”

Influence of Pressure on the Spectral Properties of Dye−DNA Supermolecules

“…However, also all the other properties on which, according to Bergström et al, the exceptional spectral features are based, change dramatically: They become pH-dependent, they depend in a characteristic fashion on the DNA adduct, the dipole moments change drastically upon excitation, and Δμ is parallel to the transition as well as to the ground state dipole moment. The experimental basis for these results is provided by our recent hole-burning Stark-effect experiments . Because the respective results are important for the interpretation of the present pressure experiments, we briefly summarize the essentials: First, we found a rather strong splitting of the holes in an external field, if the field was parallel to the polarization direction of the burning laser.…”

“…For most of the DNA strands used in the present study, detailed structural information is available 1-3 so that there is a solid basis for a detailed interpretation of the spectroscopic data. Quite recently we investigated a series of dye−DNA adducts in a glycerol/water matrix with hole-burning Stark spectroscopy to shed light on the nature of the interaction between BODIPY and DNA adducts . The major outcome of this investigation was that the dominating interaction is electrostatic and that the dipole moment at the dye probe changes strongly over the inhomogeneous band, in agreement with the strong color effect in the field-induced splitting of the spectral holes.…”