PHYSICAL-PROPERTIES OF DINITROSYL IRON COMPLEXES WITH THIOL-CONTAINING LIGANDS IN RELATION WITH THEIR VASODILATOR ACTIVITY

When studying the vasodilator activity of dinitrosyl iron complexes (D NIC) with thiol-containing ligands as NO donors, it should be taken in to consideration that these complexes depending on the content of thio ls in the environment can occur in either of two forms that differ by their EPR, gamma-resonance and optical characteristics and also by the ir vasodilator effect on isolated blood vessels. The more stable diama gnetic form appears at the ratio Fe2(+):RS(-)=1:2. It reversibly disso ciates to the monomeric paramagnetic form [(RS(-)Fe+(NO+)(2)] on incre asing the thiol content to the level 20-times and more exceeding the q uantity of iron. It is suggested that stabilization of the dimeric for m is provided by formation of RS(-)-NO+ bonds between monomeric compon ents of the dimer. This process is favored by a corresponding orientat ion of the monomers relative to each other. A high stability of the DN IC dimeric form correlates with more prolonged vasodilator effect of t his complex as an NO source. Replacement of cysteine by reduced glutat hione in dimeric and monomeric forms of DNIC increases both stability of the complexes and the duration of their vasodilator effect.