Hemes and Hemoproteins

The ENDOR literature on hemes and hemoproteins has recently been reviewed by Scholes240). Papers which are discussed in Scholes work will only briefly be summarized7.  

The magnetic parameters of aquo-Mb obtained from Fig. 44 are collected in Table 15.1. The theoretical A values for the heme and histidine nitrogen, which are about 50% smaller than the observed values, have been determined by Mun et al.242), using an extended Hiickel-type calculation. According to these authors, the agreement between theoretical and experimental values could perhaps be improved further by considering electron core polarization effects. 

In order to obtain the full hfs and quadrupole tensors of the nitrogen ligands, single crystals of diamagnetic CO-ligated ferrous Mb doped with about 10% high-spin ferric Mb have been prepared240. Preliminary data of the principal values in the heme plane are 

7 It should be noted that the quadrupole coupling constants in the papers by Scholes and coworkers 

4 From frozen solutions at gj = 2.0 (perpendicular to the porphyrin plane) 

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Woolley RG (1982) Natural Optical Acitivity and the Molecular Hypothesis. 52 1-35 Wiithrich K (1970) Structural Studies of Hemes and Hemoproteins by Nuclear Magnetic Resonance Spectroscopy. 8 53-121... 

A. J. Bearden, W. R. Durnham Iron Electronic Configurations in Proteins Studies by Moss-bauer Spectroscopy. - K Wiitkrich Structural Studies of Hemes and Hemoproteins by Nuclear Magnetic Resonance Spectroscopy. -H. A 0. Hill,A. Roder, R. J. P. Williams The Chemical Nature and Reactivity of Cytochrome P-450. - S. Lindskog Cobalt (II) in Metalloenzymes. A Reporter of Structure-Function Relations. 

Structural Studies of Hemes and Hemoproteins by Nuclear Magnetic Resonance Spectroscopy... 

In the following sections we shall first present some aspects of structure and function of hemes and hemoproteins, and then proceed to a presentation of some facts on NMR spectroscopy. Sections IV through VI deal with high resolution proton NMR experiments where information was obtained from direct observation of the hemoprotein resonances. This will be follwed by a brief survey of nuclear relaxation enhancement... 

The hyperfine shifts in the proton NMR spectra of paramagnetic hemes and hemoproteins are closely related to the electronic structures of these molecules. At present the most extensive NMR studies of the electronic spin distribution in the heme groups have been done with low spin ferric compounds, which will be discussed in this section. Procedures similar to those described here would apply to the analysis of the NMR spectra of hemoproteins in the other paramagnetic states (Table 1). 

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