Magnetic circular dichroism studies of pyridine-heme complexes in aqueous media

✍ Scribed by Toru Shimizu; Tsunenori Nozawa; Masahiro Hatano

• Book ID: 104105970
• Publisher: Elsevier Science
• Year: 1976
• Weight: 555 KB
• Volume: 6
• Category: Article
• ISSN: 0006-3061
• DOI: 10.1016/s0006-3061(00)80209-4

✦ Synopsis

The magnetic circular dichroism (hKD) spectra for Fe'+ and Fe'+ protoporphyrins (hemin and heme) with and without pyridine have revealed the sensitivity of the electronic structures of the complexes ABSTRACT formed to the solvent system: (1) The hemin in au aqueous ethylene glycol solution gave the practically same Q and Soret MCD as that in an afkahne aqueous sohrtion, indicating that there is no fundamental differences in the etectronic states between the monomeric and the dimeric hemins, and that they are both in high spin states. (2) The hemin-pyridine complex in an aqueous solution showed an MCD essentially similar to that for the hemin described above in (l), indicating that this complex is in the high spin state.

(3) The addition of pyridine to the monomeric hemin in an aqueous ethylene glycol solution induced the typical spin change from high to low like myoglobin derivatives. (4) The heme in an aqueous solution showed the MCD fairly different from that in an aqueous ethylene glycol solution, the latter showing the MCD of monomeric heme of deoxy-myoglobin. This indicates the existence of the hemeheme interaction in the aggregated or dimeric high-spin heme. (5) The heme-pyridine complexes showed the MCD characteristic of Fez+ low-spin complex irrespective of the solvent system.