P hemoglobin

Tl. Tombs, M. P., Hemoglobin-binding -globulin in human serum. Nature 186, 1055 (1960). 

Temperature dependences of the rate for direct photoinduced electron transfer process and reverse charge recombination reaction were studied in some works. As a rule both processes were found to be temperature dependent. However for [p(MP), a(Fe(III)P hemoglobin hybrid (M = Zn(II), Mg(II)) the rate constants of both processes were found to be temperature independent in the temperature interval 273-293 K [285],... 

Schendl WJ, Lipp RW, Trinker M, Hopmeirer P. Hemoglobin D ( 3 121 (C-H4) Glu—>Gln) causing falsely low and high HbA2 values in HPLC. Clin Chem 1998 44 1999-2000. 

Figure 7.27 Stabilizing free o-hemoglobin. The structure of a complex between AH.SP and -hemoglobin is shown. In this complex, the iron atom is bound to oxygen and to the distal histidine. Notice that AHSP binds to the same surface of a-hemoglobin as does p-hemoglobin. [Drawn from lYOl.pdb.]...

The major protein of the inner membrane snrface of erythrocytes, spectrin, showed increased glycosylation in diabetics (M13). On a protein weight basis, spectrin glycosylation was about twice that for hemoglobin, although spectrin contains 6.8% lysine compared with 7.8% for a-hemoglobin and 7.6% for p-hemoglobin. 

Several pure hemoglobin solutions were later produced on a large scale for experimental use. A procedure was described for crystallization of hemoglobin and the product was evaluated in a series of animal trials (38—41). A 6 g/dL hemoglobin solution that had a P q of about 2.4—2.7 kPa (18—20... 

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...

The oxygen affinity of the derivative was shown to be about half that of unmodified hemoglobin under similar conditions, but a degree of cooperativity was preserved. Kquilihrium and kinetic ligand-binding studies on this derivative have been interpreted (62) to show a perturbed R state. It is beheved that although the reaction is between the two P-chains, aP-dimers function independentiy, probably through a flexible connection. 

Thus the large-scale preparation of pyridoxylated hemoglobin seems to result in mixtures of reaction products. These probably represent modifications at either or both a- and P-antino-terrmnal residues as well as surface lysines. A partial characterization of the mixture has been carried out (74). 

Bis-Pyndoxal Tetraphosphate. A second class of bifunctional reagents, described in 1988, involves two pyridoxal groups linked by phosphates of different lengths (89). As shown in Table 4, the yield of intramolecularly cross-linked hemoglobin increases dramatically with increasing length of the phosphate backbone. It is beheved that the site of reaction of (bis-PL) is between the amino-terminal amino group of one P-chain and the... 

In 1982 a study of the usefulness of DBBF in the production of a blood substitute was reported (99). A single modification achieved the dual goals of reduced oxygen affinity and restricted tetramer—dimer dissociation. This work was confirmed in 1987 (98). The product, called aa-hemoglobin, was formulated in Ringer s lactate. P q under physiologic conditions is 3.7 kPa (28.0 torr). Hill s parameter is 2.2, and the Bohr effect was reduced (100). Plasma retention was increased, and the product appeared to be less heterogeneous than some of the other derivatives under study. Its production was scaled up by Baxter Healthcare Corp., under contract to the U.S. Army. 

Optimization of the ATP—hemoglobin reaction conditions produced a preparation having a markedly reduced oxygen affinity. Five fractions from a reaction mixture, when isolated, were found to have P q values ranging from 1.1 to 5.0 kPa (8 to 38 torr), most withUtfle cooperativity (118). These results are consistent with those found with other polyfunctional reagents that react on the surface of hemoglobin. 

PSS-SG composite film was tested for sorption of heme proteins hemoglobin (Hb) and myoglobin (Mb). The peroxidaze activity of adsorbed proteins were studied and evaluated by optical and voltammetric methods. Mb-PSS-SG film on PG electrode was shown to be perspective for detection of dissolved oxygen and hydrogen peroxide by voltammetry with linear calibration in the range 2-30 p.M, and detection limit -1.5 p.M. Obtained composite films can be modified by different types of biological active compounds which is important for the development of sensitive elements of biosensors. 

Sickle-cell anemia is the classic example of an inherited disease that is caused by a change in a protein s amino acid sequence. Linus Pauling proposed in 1949 that it was caused by a defect in the hemoglobin molecule he thus coined the term molecular disease. Seven years later Vernon Ingram showed that the disease was caused by a single mutation, a change in residue 6 of the P chain of hemoglobin from Glu to Val. 

Hemoglobin is a tetramer built up of two copies each of two different polypeptide chains, a- and (5-globin chains in normal adults. Each of the four chains has the globin fold with a heme pocket. Residue 6 in the p chain is on the surface of a helix A, and it is also on the surface of the tetrameric molecule (Figure 3.13). 

Figure 3.14 Sickle-cell hemoglobin molecules polymerize due to the hydrophobic patch introduced by the mutation Glu 6 to Val in the P chain. The diagram (a) illustrates how this hydrophobic patch (green interacts with a hydrophobic pocket (red) in a second hemoglobin molecule, whose hydrophobic patch interacts with the pocket in a third molecule, and so on. Electron micrographs of sickle-cell hemoglobin fibers are shown in cross-section in (b) and along the fibers in (c). [(b) and (c) from J.T. Finch et al., Proc. Natl. Acad. Set. USA 70 718-722, 1973.)...

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