Changes in the mechanical and electric parameters of bilayer lipid membranes in their interaction with hematoporphyrin

The interaction of hematoporphyrin IX (HP) with artificial bilayer lipid membranes (BLMs) has been studied. It has been found that after dark incubation of BLMs in a HP solution (at concentrations from $10^{-6}$ to $3 \cdot 10^{-5}$ M) the conductance of the BLMs does not change very much, the elasticity modulus ( $E_{\perp}$ ) and the dynamic viscosity coefficient $\eta$ diminish by 21.9-31.3%, while the membrane potential $U_1$ becomes negative (-50 mV). Irradiation of a modified BLM by a He-Ne laser leads to an increase of the parameters $E_{\perp}$ aud $\eta$ by 40.7 to 66.2%, to a decrease of $U_1$ to -20 mV, and also to irreversible changes in the mechanical properties of the membrane. Binding of HP with BLM proceeds noncooperatively with the constant $К = 10^{5}$ $М^{-1}$.