Characterization of Ground State Electron Configurations of High-Spin Quintet Ferrous Heme Iron in Deoxy Myoglobin Reconstituted with Trifluoromethyl Group-Substituted Heme Cofactors.

We introduced trifluoromethyl (CF) group(s) as heme side chain(s) of sperm whale myoglobin (Mb) in order to characterize the electronic nature of heme Fe(II) in deoxy Mb using F NMR spectroscopy. On the basis of the anti-Curie behavior of CF signals, we found that the deoxy Mb is in thermal equilibrium between the B, (d)(d)(d)(d)(d), and E, (d)(d)(d)(d)(d), states of the heme Fe(II), i.e.

Characterization of the interaction between heme and a parallel G-quadruplex DNA formed from d(TTGAGG).

Structure-function relationships of complexes between heme and G-quadruplex DNAs have attracted interest from researchers in related fields. A carbon monoxide adduct of a complex between heme and a parallel G-quadruplex DNA formed from hexanucleotide d(TTGAGG) (heme-[d(TTGAGG)] complex) has been characterized using H NMR spectroscopy, and the obtained results were compared with those for the heme-[d(TTAGGG)] complex previously studied in order to elucidate the effect of the incorporation of an A-quartet into stacked G-quartets in the 3'-terminal region of the DNA on the structure of the heme-DNA complex. We found that a π-π stacking interaction between the porphyrin moiety of the heme and the 3'-terminal G-quartet of the DNA is affected by the nature of the stacked G-quartets.