Deoxyhemoglobin

Fig. 2. Reaction of diphosphoglycerate (2,3-DPG) and deoxyhemoglobin. The molecule fits into the central cavity of hemoglobin and forms salt bridges with valine NA(I)p, histidines NA2(2)p, H2I(I43)p, and lysine EF6(82)p. A, E, and E correspond to specific hemoglobin hehces and NA is the sequence...

In deoxyhemoglobin, histidine F8 is liganded to the heme iron ion, but steric constraints force the Fe His-N bond to be tilted about 8° from the perpendicular to the plane of the heme. Steric repulsion between histidine F8 and the nitrogen atoms of the porphyrin ring system, combined with electrostatic repulsions between the electrons of Fe and the porphyrin 77-electrons, forces the iron atom to lie out of the porphyrin plane by about 0.06 nm. Changes in... 

In addition to COg, Cl and BPG also bind better to deoxyhemoglobin than to oxyhemoglobin, causing a shift in equilibrium in favor of Og release. These various effects are demonstrated by the shift in the oxygen saturation curves for Hb in the presence of one or more of these substances (Figure 15.35). Note that the Og-binding curve for Hb + BPG + COg fits that of whole blood very well. 

Figure 6-9. The Bohr effect. Carbon dioxide generated in peripheral tissues combines with water to form carbonic acid, which dissociates into protons and bicarbonate ions. Deoxyhemoglobin acts as a buffer by binding protons and delivering them to the lungs. In the lungs, the uptake of oxygen by hemoglobin releases protons that combine with bicarbonate ion, forming carbonic acid, which when dehydrated by carbonic anhydrase becomes carbon dioxide, which then is exhaled.

Figure6-10. Mode of binding of 2,3-bisphosphoglycerate to human deoxyhemoglobin. BPG interacts with three positively charged groups on each p chain.

Based on Arnone A X-ray diffraction study of binding of 2,3-diphosphoglycerate to human deoxyhemoglobin. Nature 1972 237 146. Reproduced with permission.)... 

Figure 6-11. Representation of the sticky patch (A) on hemoglobin S and its "receptor" (A) on deoxyhemoglobin A and deoxyhemoglobin S. The complementary surfaces allow deoxyhemoglobin S to polymerize into a fibrous structure, but the presence of deoxyhemoglobin A will terminate the polymerization by failing to provide sticky patches. (Modified and reproduced, with permission, from Stryer L Biochemistry, 4th ed. Freeman, 1995.)...

C20-0111. Oxyhemoglobin is bright red, but deoxyhemoglobin is blue. In both cases the iron is in the +2 oxidation state. Give a detailed explanation for the difference in color. How would you test your hypothesis Based on your explanation, what color would you predict for a sample of blood that is saturated with carbon monoxide ... 

Deoxyhemoglobin can bind more carbon dioxide than oxygenated hemoglobin. Therefore, unloading of oxygen in the tissues facilitates loading... 

Figure 4.4 Quaternary structure of deoxyhemoglobin tetramer visualized using Wavefunc-tion, Inc. Spartan 02 for Windows from PDB data deposited as 4HHB. See text for visualization details. Printed with permission of Wavefunction, Inc., Irvine, CA. (See color plate.)...

M. Oda, Y. Yamashita, G. Nishimura, and M. Tamura. Determination of absolute concentration of oxy- and deoxyhemoglobin in rat head by time-resolved beer-lambert law. SPIE, 2389 770-778, 1995. 

Y. Yamashita, M. Oda, E. Ohmae, and M. Tamura. Continuous measurement of oxy- and deoxyhemoglobin of piglet brain by time-resolved spectroscopy. OSA TOPS, 22 205-207, 1998. 

Hemoglobin is directly measured and is an independent and continuous variable However, and probably because at any one time a number of forms and conformations (oxyhemoglobin, deoxyhemoglobin, methemoglobin, etc.) of hemoglobin are actually present the distribution seen is not typically a normal one, but rather may be a multimodal one. Here a nonparametric technique such as the Wilcoxon or multiple rank-sum is called for. 

B. Chance, J. Leigh, H. Miyake, D. Smith, S. Nioka, R. Greenfield, M. Finlander, K. Kaufmann, W. Levy, M. Young, P. Cohen, H. Yoshioka, and R. Boretsky, Comparison of time-resolved and -unresolved measurements of deoxyhemoglobin in brain, Proc. Natl. Acad. Sci. 85, 4971 1975 (1988). 

Subunit contacts need to be relatively extensive and stable if they are to ensure subunit association in the absence of a covalent link. However, in some cases a subunit contact can shift back and forth between two different stable positions, as has been demonstrated for oxy- versus deoxyhemoglobin (Perutz, 1970). Allosteric control can then be exerted by any factors which either affect the local conformation or bind between the subunits. A less elegant but even more extreme example is lamprey hemoglobin, which dissociates altogether in the oxy form (Hendrickson and Love, 1971). 

Figure A2.10 Protein structure human deoxyhemoglobin. Source Protein Data Bank,PDB ID lA3N.Tame J, Vallone B. http //www.rcsb.org/pdb/cgi/explore.cgi job= graphics pdbId=lA3N page=0 opt=show size=250 [accessed April 16, 2003]. Used with permission.)...

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