Article

Binding of porphyrins to biological macromolecules is important to be studied as an approach to keeping them in stable, effective and safe dosage forms. In this work we show the interaction of three porphyrin compounds: Hematoporphyrin IX, Mn- and Fe-porphyrins with plant lectin Wheat germ agglutinin (WGA). Porphyrin binding to WGA was monitored by the changes in the intrinsic protein fluorescence. Conformational changes due to the formation of WGA-porphyrin complexes, were shown by the hyperbolic binding curves. The calculated dissociation constants K_D (0.16 μМ to 0.24 µМ) indicate high affinity of WGA for the three porphyrins. Most probably they occupy the same high affinity sites. In conclusion, since WGA binds cancer cells and interacts with antitumor compounds, it could be useful as a drug delivery molecule.