Deoxy-haemoglobin

Fermi, G., et al. The crystal stmcture of human deoxy-haemoglobin at 1.74 A resolution. /. Mol. Biol. 

FIGURE 13.7 The ai—p2 interface in (a) human deoxy haemoglobin and (b) oxy-haemoglobin. (Adapted from Voet Voet, 2004.)... 

The main problem of protein SERS study is that the protein native structure can be disturbed by its interaction with a metal surface. SERS spectra of oxy- and deoxy- haemoglobin indicated a partial denaturation of haemoglobin when adsorbed on Ag colloidal NPs (Smulevich and Spiro 1985). Biocompatible coating of the metal surface by SAMs of alkanethiols terminated with NH2- or COOH- groups mediating protein immobilization was used to preserve its native structure (Murgida and Hildebrandt 2006). Another way to keep the natural protein structure is the preparation of a specific SERS-active substrate where the protein molecule is more... 

Fig. 16. Approximate representation of the binding of 2,3-diphosphoglycerate (DPG) to deoxy-haemoglobin. Black bonds accurately represent the structure of deoxyhaemoglobin in the absence of DPG, red bonds show an approximation to the structure in the presence of DPG, based on the description in [72A], broken lines indicate likely salt bridges or other ionic interactions. The molecular dyad is perpendicular to the page, at the centre of the diagram. Strict molecular symmetry is lost when DPG binds, because of lack of symmetry in the DPG molecule. Binding DPG causes changes in the conformations of the N-terminus, His NA2 and His H21 it also causes movements of the A helices into the central cavity (as illustrated) and of the H helices away from the central cavity (not illustrated).

Figure 13.6 The haem group and its environment in the deoxy form of the human haemoglobin a-chain. Only selected side chains are shown, and the haem 4 propionate is omitted for clarity. (From Gelin and Karplus, 1977. Copyright (1993) National Academy of Sciences, USA.)...

The pulse oximeter is a non-invasive device used to monitor the percentage saturation of haemoglobin (Hb) with oxygen (Spo2). The underlying physical principle that allows this calculation to take place is that infrared light is absorbed to different degrees by the oxy and deoxy forms of Hb. 

Figure 1.6 The structure of the haem residue in deoxy- and oxy-haemoglobins. In deoxy-Hb the bonding of the iron is pyramidal whilst in oxy-Hb it is octahedral...

C(NH2)2+ unit of arginine, via the formation of hydroxylamine. It can be characterized by ESR spectroscopy using deoxy-myoglobin or -haemoglobin with which it reacts to give nitrosyl derivatives having well-defined spectra. Its chief biological role seems to be as a vasorelaxant (Moncada et al., 1988). 

A comparison of the deoxy- and oxy-haemoglobin structures reveals a number of important differences. Whereas in the T (deoxy) state the Fe atom is out of the haem plane, on oxygenation it moves into the plane of the now undomed porpyrin, pulling the proximal His F8 and the F-helix, to which it is attached, with it (Figure 13.6),... 

The absorption in tissue is dominated by oxy-haemoglobin, deoxy-haemo-globin, lipids, and water [121]. The extinction coefficients of the tissue constituents are shown in Fig. 5.41, left. Absorption spectra of tissue measured in vivo are shown right. There is an absorption window from approximately 650 to 900 nm. Therefore, NIR light can be transmitted and detected through tissue layers as thick as 10 cm. Absorption coefficients for various types of tissue are given in [367]. 

Neutron experiments were first made on haemoglobin [98,99,147,166,167] and were extended to myoglobin [44,168], lysozyme [169] and catalase [170] as models of typical globular proteins. In parallel with X-ray scattering, the haemoglobin work (mainly in H20) identified a conformational change between the oxy- and deoxy-forms which was reflected in an difference of 0.054 nm in H20 buffers. Scattering curve comparisons to <2 = 3 nm with the crystal structures verified this. 

J.R.H. Tame and B. Vallone, The Structures of Deoxy Human Haemoglobin and the Mutant Tyra42 His at 120K. Acta Crystal. D, 56, 805-811,2000. 

R.C. Liddington, Z. Derewenda, E. Dodson, R. Hubbard, and G. Dodson, High resolution crystal structures and comparisons of T state deoxy and two liganded T state hemoglobins T (aoxy) Haemoglobin and T (met) Haemoglobin. J. Mol. Biol, 228,551-579,1992. 

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