Effects of two polyanions (heparin, Nafion) on absorption and CD spect
ra in the Soret region, and on fluorescence of ferricytochrome c were
investigated. The conformational state of ferricyt c in the complexes
with studied polyanions is significantly different. Whereas heparin af
fects the structure in the heme region of ferricyt c only slightly (fe
rricyt cremains in a native-like state), the influence of Nafion is mo
re expressive (the Met-80 - heme iron bond and the deeply buried regio
n around Trp-59 are perturbed). Shift of the pK of the transition from
neutral low-spin state to acidic high-spin state to higher pH values
was observed.