Persistent Spectral Hole Burning for a Free-Base Porphyrin Doped in a DNA-Lipid Complex Film

We performed persistent spectral hole burning for a free-base porphyrin (TMPyP) doped in a DNA-lipid complex film. The microscopic environments of the TMPyP intercalating or outside-binding to the double helix of the DNA-lipid complex is evaluated. The real inhomogeneous width for the TMPyP/DNA-lipid complex is similar to that for a TMPyP/poly(vinyl alcohol) system. In temperature cycling experiments the hole begins to broaden at 40 K, whereas the hole area does not show marked decrease below 100 K. The irreversible hole broadening is attributed the relaxation of the alkyl chain in the lipid part. No decrease in hole area during the temperature cycle is supposed to reflect the binding structure of the TMPyP molecules to the double helix in the DNA-lipid complex.