13C chemical shifts and 13C–15N and 13C–57Fe spin coupling constants as structural probes for haem environments. 13C N.m.r. study of the binding of 15N and 13C labelled alkyl isocyanides to myoglobin and synthetic porphyrins

Abstract

A ¹³C n.m.r. study of ¹³C and ¹⁵N labelled alkyl isocyanides (R¹⁵N¹³C) bound to the heam iron(II) atom labelled with ⁵⁷Fe in netural myoglobin and synthetic tetraphenyl- and octaethyl-porphyrin iron(II) shows that the iron-bound isocyanide ¹³C chemical shifts and ¹⁵N–¹³C coupling constants are sensitive to varioation of the R group and the presence of globin, while the one-bound ¹³C–⁵⁷Fe coupling constant is not susceptible to these structural factors.