Modelling heme d₁

Abstract

The heme d, macrocycle of Ps. aeruginosa dissimilatory nitrite reductase is an iron porphyrin-3,8-dione with a 17-acrylate substituent. We have compared the RR properties of Cu-d,, the copper(I1) TME of extracted heme d,, with those of models that differ only with respect to the acrylate: Cu-17-acrylate-mesoporphyrin-3,8-dione (2) and Cu-mesoporphyrin-3.8-dione (3). The RR spectrum of Cu-d, is very similar to that of 2, including v(C = 0) at _ 1720 cm-I. Replacement of the acrylate with propionate changes the spectrum markedly. For example, the v(C = 0) mode of 3 shifts to 1712 cn-i, and peaks of Cu-d, and 2 at u 1400 and N 1535 cn-i are shifted or absent from the spectrum of 3. FTIR spectra of 2 and 3 also differ in their v,,(C = 0) frequencies. The acrylate thus has a surprisingly strong influence on the electronic structural and spectral properties of heme d,. These data provide a foundation for studies of the novel biological porphyrindione macrocycles.

Spectroscopic analysis of models for heme d1: isomeric copper(II) porphyrindiones

“…We previously suggested that the v(C=0) modes of the two oxo groups of Cu-dx were accidentally degenerate. 25 For dione models 2-5, 7, and 8, neither the FTIR spectra nor the RR spectra display separate voxo(C=0) modes. The v0X0(C=O) modes of 2-5,7, and 8 need not necessarily be accidentally degenerate to display the observed lack of splitting.…”

Electrochemical Titrations of Nickel β-Oxoporphyrins with Imidazole

“…(5,6) electronic, (1,5,6,7) and vibrational spectroscopic (5,8) properties of this class of compounds.…”