Hemoproteins model compounds

The purpose of synthesising hemoprotein model compounds is twofold. First, it gives an understanding into the nature and operation of those criteria in natural systems. Secondly, by constructing models that mimic the supramolecular ability of enzymes for binding, recognition, and catalysis, the models themselves may find practical application, e.g. in he oxidation of organic compounds. ... 

Up to now, two types of iron compounds have been studied with ENDOR, namely heme compounds (hemoproteins and some heme model compounds) and iron-sulfur proteins. For comprehensive summaries of the corresponding EPR work, the reader is referred to the literature234-2371. 

Comparisons between R- and T-state hemoglobins on the one hand and a variety of synthetic model compounds on the other have allowed an evaluation of the possible occurrence and importance of electronic, proximal-base tension, and distal-side steric effects on the kinetics of ligation of CO and 02. Although all of these effects could influence the reactivities of hemoproteins, we conclude that hemoglobin reactivity and cooperativity are controlled predominantly by the presence or absence of proximal-base tension. 

Furthermore, the regioselectivity of hydroxylation of alkanes or epoxidation of alkenes appears to be dependent on the nature of the distal environment of the metal center [196, 197]. It has been postulated that the access to the iron is controlled either by the superstructures in model compounds or by the protein chains present in the vicinity of the iron in the hemoprotein active site. Thus,... 

I.P. Gerothanassis, NMR studies of hemoproteins and synthetic model compounds in the solution and solid states, Prog. Nucl. Magn. Reson. Spectrosc. 26 (1994) 239. 

Theoeretical models proposed by Griffith (36, 38) and Kotani (59, 60) are now generally employed for the interpretation of the spectral and magnetic properties of hemoproteins. In his recent review Weissbluth (106) gave a detailed account of the calculations involved in these models. The present discussion is limited to a brief outline of the treatment of low spin ferric heme compounds, and the presentation of some results which will be useful for the analysis of the NMR data. 

These results and conclusions contrast the suggestion that model heme compounds bind CO much more strongly than do hemoproteins (32). In the solid state, models appear to bind CO irreversibly at room temperature (18, 32), but this is in part due to the high affinity of all hemes, and may, in addition, reflect difficulties in removing the CO from the solid. In solution, models bind CO very strongly... 

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