Deoxy-myoglobin

Fig. 3.2 The structure of myoglobin (deoxy form, PDB entry 1AGN, at 1.15 A resolution [3f]). The heme active center is highlighted (van der Waals spheres), as are the proximal and distal histidines (His93 and His64, respectively, shown as sticks).

Fig. 6.8 Mossbauer spectra of deoxy-myoglobin, obtained in applied fields of 2 T (left) and 6.2 T (right) at temperatures of 4.2, 10, 15, 20, 30 and 50 K (from bottom to top). The solid lines were calculated using a relaxation model. (Reprinted from [34] copyright 1994 by Springer-Verlag)...

Sage et al. reported the complete vibrational spectrum of the iron site in deoxy-and CO-myoglobin [110]. The spectrum of photolyzed CO-myoglobin (frozen solution) resembles that of Mb. Because of high-resolution and reasonable statistics, they... 

For CO-myoglobin a Fe-CO stretch at 502 cm and a Fe-C-O bend at 572 cm has been observed [112]. The drastic increase of the out-of-plane stretch compared to deoxy- and metmyoglobin is due to the strong covalent Fe-CO bond. Raising the temperature from 50 to 110 K led to a broad resonance at around 25 cm which has been assigned to the translational motion of the whole heme moiety. 

The PDOS of the iron in deoxy- and CO-myoglobin and of myoglobin with different degrees of water content was also determined by Achterhold et al. [112, 113]. They found that the modes with an energy larger than 3 meV (24 cm ) are harmonic at physiologically relevant temperatures. Those below 3 meV exhibit a... 

The biochemical activity and accessibility of biomolecule-intercalated AMP clays to small molecules was retained in the hybrid nanocomposites. For example, the absorption spectrum of the intercalated Mb-AMP nanocomposite showed a characteristic soret band at 408 nm associated with the intact prosthetic heme group of the oxidised protein (Fe(III), met-myoglobin) (Figure 8.9). Treatment of Mb with sodium dithionite solution resulted in a red shift of the soret band from 408 to 427 nm, consistent with the formation of intercalated deoxy-Mb. Reversible binding of CO under argon to the deoxy-Mb-AMP lamellar nanocomposite was demonstrated by a shift in the soret band from 427 to 422 nm. Subsequent dissociation of CO from the heme centre due to competitive 02 binding shifted the soret band to 416nm on formation of intercalated oxy-Mb. 

Fig. 8.9 UV—Vis spectra of intercalated biomolecules assembled AMP. Soret band absorptions for (A) oxidized myoglobin (met-Mb) and after dithionite reduction (deoxy-Mb), and (B) after CO (CO-Mb) and 02 bindingto intercalated deoxy-Mb.

X-ray crystallographic structures of myoglobin and hemoglobin were first completed in 19662 and 19753, respectively. Since then, many other X-ray crystallographic studies of deoxy- and oxy- as well as met-myoglobin and hemoglobin have been carried out.22,24 Additionally, researchers have studied the carbon monoxide bound moieties MbCO and HbCO as well as MbNO. Site-directed mutagenesis of residues near the active sites of Mb and Hb have yielded... 

Recent work has resolved some of the issues that complicate direct electrochemistry of myoglobin, and, in fact, it has been demonstrated that Mb can interact effectively with a suitable electrode surface (103-113). This achievement has permitted the investigation of more complex aspects of Mb oxidation-reduction behavior (e.g., 106). In general, it appears that the primary difficulty in performing direct electrochemistry of myoglobin results from the change in coordination number that accompanies conversion of metMb (six-coordinate) to reduced (deoxy) Mb (five-coordinate) and the concomitant dissociation of the water molecule (or hydroxide at alkaline pH) that provides the distal ligand to the heme iron of metMb. 

Franzen, S., Bohn, B., Poyart, C., and Martin, J. L. 1995. Evidence for sub-picosecond heme doming in hemoglobin and myoglobin A time-resolved resonance Raman comparison of carbonmonoxy and deoxy species. Biochemistry 34 1224-37. 

In general, percent metmyoglobin is reported and not percent deoxy- or percent oxymyo-globin. Formulas for the two ferrous myoglobin forms can be obtained from Krzywicki (1982). 

Treat a myoglobin stock solution (on ice) with sodium hydrosulfite at a rate of 0.1 mg sodium hydrosulfite to 1 mg myoglobin. Vortex 10 sec to reduce metmyoglobin to deoxy- and oxymyoglobin. 

Figure 6-3 Schematic diagram of deoxy- and oxy-myoglobin near the active site.

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