Met-myoglobin

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. 

A series of enzyme and proteins (met-myoglobin, lysozyme, met-hemoglobin, glucose oxidase, a-chymotrypsin) was also immobilized in a-ZrP by Kumar et al. [134]. Binding constant values clearly confirm the high affinity of the various proteins with the host structure (Table 15.4). 

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... 

The kinetics of reactions of NO with ferri- and ferro-heme proteins and models under ambient conditions have been studied by time-resolved spectroscopic techniques. Representative results are summarized in Table I (22-28). Equilibrium constants determined for the formation of nitrosyl complexes of met-myoglobin (metMb), ferri-cytochrome-c (Cyt111) and catalase (Cat) are in reasonable agreement when measured both by flash photolysis techniques (K= konlkQff) and by spectroscopic titration in aqueous media (22). Table I summarizes the several orders of magnitude range of kon and kQs values obtained for ferri- and ferro-heme proteins. Many k0f[ values were too small to determine by flash photolysis methods and were determined by other means. The small values of kQ result in very large equilibrium constants K for the... 

An obvious extension to 3D spectroscopy from 2D spectroscopy is the homonu-clear NOESY-NOESY [34]. There are two t variable times and one tj, which after Fourier transform provide three frequency domains. The 3D NOESY-NOESY spectrum of met-myoglobin cyanide, which contains low spin iron(III) in a heme moiety (see Fig. 5.7), has been successfully measured [35]. In Fig. 8.22 a slice of the 3D spectrum is shown at the I2-CH3 height. On the diagonal it shows all the dipolar connectivities between I2-CH3 and other protons off-diagonal... 

Fig. 8.22. Cross-section of the 600 MHz 3D NOESY-NOESY spectrum of met-myoglobin cyanide. The slice is taken at the 12-CH3 height. The inset shows the simulated cross-section involving the 12-CHj, 13-Ha and 13-Ha signals [35],...

Fig. 8.23. NOESY spectrum (A) and NOE-NOESY spectrum (B) of met-myoglobin cyanide [36], The latter spectrum is obtained by pre-irradiation of the I2-CH3 signal.

In fresh meat and in the presence of oxygen, there is a dynamic system of three pigments, oxymyoglobin, myoglobin, and met-myoglobin. The reversible reaction with oxygen is... 

The nitrophorins of the kissing bug, Rhodnius prolixus, are unique NO-binding heme proteins, in that they are stable as Fe heme centers and are not autoreduced by excess NO in the solution as are other heme proteins such as met-myoglobin consistent with this property, their reduction potentials are about 300 mV more negative than that of met-myoglobin (E° 0 mV vs. SHE at pH = 7.5) is... 

Table 4 Mossbauer parameters of high-valent intermediates of peroxidases, met-myoglobin treated with H2O2 and two tetramesitylporphyrin(TMP) model systems ...

Ferulic acid (XIX) is found ester-linked to polysaccharides in the primary cell walls of Graminaceae, which include cereals and grasses [95]. Ferulic acid is an effective scavenger of free radicals [96] and can also protect low density lipoprotein against met-myoglobin-induced oxidative damage... 

IVXH. Yang, F, Phillips Jr., G. N., Structures of Co-, Deoxy- and met-Myoglobins at Various Ph Values. To be published. 

Results from an early unrefined met myoglobin neutron analysis ( ) based on the x ray structure by Watson and Kendrew ( ) showed a total of 106 water peaks. In that analysis, only peaks that had a peak height equivalent to one-half D2O molecule were considered. More recently, Takano (O, in a refined high resolution x-ray analysis of met myoglobin, found 72 water molecules, and in the present refined neutron analysis of CO-Mb, only AO water molecules were found. These water molecules were identified in a difference map where the features depicting the protein had been subtracted. The protein structure itself had been refined by successive real-space refinement of eight... 

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