The diaminoacid derivatives of protoporphyrin IX are promising in applications as photosensitizers in diagnosis and photodynamic therapy. Particularly derivatives with good water-solubility generate a lot of interests. It has been shown that due to the presence of selected amino acids residues attached to the porphyrin ring, these novel compounds penetrate more easily into tumor tissues and also clear from healthy tissues faster than others protoporphyrin-based photosensitizers. Nevertheless, the knowledge about chemistry and physical properties of these materials it still not sufficient. The one of not answered question is the role of Fe ions.
Several experimental techniques have been used for investigation of iron in protoporhyrin-like structures, but only few papers present the x-ray absorption approach. This motivated us to apply the XANES and EXAFS analysis to the study of ionic states and distribution of atoms around Fe in different diaminoacid derivatives of protoporphyrin. The content of Fe ions in the studied compounds are low and samples are nonconductive, therefore the only method of spectra detection is the fluorescence detection. Additionally, a set of iron-containing samples having different ionic states of Fe atoms was measured as a reference compounds. Measurements of Fe K-edges were performed at the HASYLAB beamline A1 using five-element Si detector. The samples were cooled down to LN temperature.
The differences in the position and intensity of the peaks of the radial distribution function can already be seen in raw data. To get more quantitative information, a model of the atomic distribution around the iron atom in the investigated samples was designed.
This work was supported in part by the Polish State Committee for Scientific Research (Grants No: 2-P03B-106-25, 2-P03B-055-24, and 2-P03B-090-19) and by the IHP-Contract HPRI-CT-2001-00140 and G1MA-CI-2002-4017 (CEPHEUS) of the European Commission.