Magnetic circular dichroism of heme-isocyanide complex in aqueous media

✍ Scribed by Toru Shimizu; Tsunenori Nozawa; Masahiro Hatano

• Book ID: 104105866
• Publisher: Elsevier Science
• Year: 1976
• Weight: 533 KB
• Volume: 6
• Category: Article
• ISSN: 0006-3061
• DOI: 10.1016/s0006-3061(00)80046-0

✦ Synopsis

The nature of the ethyl isocyanide compbxes of fen-i-and ferroheme was investigated iu terms of the magnetic circular dichroism @ICD) spectroscopy. The complex formation of heme with ethyl isocyanide was criticalIy dependent on the solvent system, thus, on structures of heme before addition of the Iigaud. The MCD spectra of the heme ethyl isocyanide complexes revealed that:

(1) The addition of ethyl isocyanide to both ferri-and ferro-heme in an aqueous solution gave respective high-spin heme complexes with no more than one ethyl isocyauide molecrde per one heme.

(2) The ferro-heme with ethy1 isocyanide iu an aqueous ethanol sohrtion formed a typical monomeric low spin ferro-hemochrome with two Iigauds (ethyl isocyanide) on both sides of the heme plane.

(3) In the presence of excess ethyl isocyanide in an aqueous ethanoi solution the ferri-heme gave au MCD spectrum similar to that for the monomeric low spin ferro-hemochrome. Therefore, ethyl isocyanide was believed to reduce the ferri-heme in an aqueous ethanol solution.

(4) The ferro-heme ethyl isocyanide compIex in an aqueous solution offered a Faraday B term around 450 nm instead of an apparent Faraday A term observed for the ethyl isocyanide complex of the cytochrome P450. These results are not consistent with the view that the ferro-heme ethyl isocyanide complex in au aqueous solution can be a heme chromophore model for the cytochrome P-450 ethyl isucyanide complex_