Hemoglobin ferri

Fig. 12. Schematic views of bis-histidyl ferri-, ferro-, and CO-ferro-heme-hemopexin. Unlike myoglobin with one open distal site, heme bound to hemopexin is coordinated to two strong field ligands, either of which a priori may be displaced by CO. This may well produce coupled changes in protein conformation like the Perutz mechanism for 02-binding by hemoglobin (143). The environment of heme bound to hemopexin and to the N-domain may be influenced by changes in the interactions of porphyrin-ring orbitals with those of aromatic residues in the heme binding site upon reduction and subsequent CO binding.

Replacement of the proximal histidyl residue (87 in the a chain and 92 in the chain), which occupies the fifth coordinate position of the iron of heme, by a tyrosyl residue (Hb-M-Iwate and Hb-M-Hyde Park, respectively) results in the formation of Met( = ferri) hemoglobin. It seems likely that the iron atoms in these two hemoglobins are covalently linked to the distal histidyl residue (a-58 and j8-63, respectively) whereas an ionic link is present between the iron atom and the OH group of the tyrosyl residue in position a-87 or 8-92. Replacement of the distal histidyl residue, a-5S or j8-63, by a tyrosyl residue is found in the methemo-globins M-Boston and M-Saskatoon. This substitution also results in an ionic link between the phenolic oxygen of this residue and the ferric iron. The fifth methemoglobin, Hb-M-Milwaukee, has similar properties be-... 

The ferryl derivative of hemoglobin then oxidises HK, finally returning to the ferri- state. 

The most accurate and extensive data on the oxygen equilibrium are those obtained by Ferry and Green for horse hemoglobin in phosphate and borate buffers. Ferry and Green remarked that their curves of y (the ratio... 

The only compound known so far in which ferric iron is magnetically comparable with that of ferritin is methemoglobin (ferri-hemoglobin) in alkaline solution, which is the first case in which this particular level of susceptibility has been discovered, in work done by Pauling and Coryell (12). Here the susceptibility is slightly higher, suggesting some orbital contribution to the susceptibility. 

Similar effects are found in solutions of some, but not all, proteins. Thus horse hemoglobin (Richards, 177) and j3-lactoglobulin (E. J. Cohn, J. D. Ferry, and M. H. Blanchard, unpublished studies, quoted in ref. 39, Chapter 24 Gronwall, 85) become decidedly more soluble in the presence of glycine. The relative solvent effect of glycine on these two proteins, and on cystine, asparagine and glycine is shown in Fig. 7 ... 

Wu (218) successfully employed low temperature-ethanol precipitation in the preparation of undenatured proteins and Ferry, Cohn and Newman (71, 72) employed ethanol-water, at —5° C., at low ionic strengths, as a medium for studying the solubility of egg albumin and horse hemoglobin in solvents of low dielectric constant. They showed that the solvent action of neutral salts under these conditions was much greater than in water and that both these proteins could be successfully recrystallized, after exposure to 15-25 per cent ethanol at —5 for long periods, provided the ethanol was removed before the temperature was raised. 

From the data of Ferry and Green on horse hemoglobin, it might appear that the curve of Y vs. log p is truly symmetrical. On the supposition that it is so, Pauling (143) has given a remarkable analysis... 

Based on data of Ferry and Green (48) on horse hemoglobin. 

Fig. 9. pH dependence of the oxygenation equilibrium of hemoglobin. The points and the broken curve represent the data of Ferry and Green. The solid curves are calculated from the broken curve by means of Eq. (33) and Wyman s constants listed in Table V. 

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