Electric dichroism studies on ferriheme– and ferroheme–poly( L ‐lysine) complexes at pH 9–12

Transient electric dichroism has been measured for the ferriheme–poly( L ‐lysine)[(Lys) n ], ferroheme–(Lys) n , and ferroheme–(Lys) n –carbon monoxide (CO) solutions at pH 9–12. The Soret absorption maximum in electronic spectrum (λ), the reduced linear dichroism (ρ ∞ ) at complete orientation and the calculated angle (ϕ) between the porphyrin plane of a bound heme and the oriented polymer axis are determined for the following complexes: a ferriheme–(Lys) n complex at pH 9.5–10.5 (λ = 420 nm, ρ ∞ = 0.50, and ϕ = 19°), a ferroheme–(Lys) n complex at pH 9.5–10.2 (λ = 432 nm, ρ ∞ = 0.77, and ϕ = 0°), and a ferroheme–(Lys) n –CO complex at pH 9.25 (λ = 430 nm, ρ ∞ = 0.38, and ϕ = 24°). Based on the above data, the validity of the structures of heme–(Lys) n complexes proposed by other investigators is discussed.