Hemoglobin physiological importance

Perhaps the most physiologically important metalloprotein to be S-nitrosated by NO is hemoglobin (Hb). The S-nitrosation of Hb-Cys 93 by NO was first demonstrated by Stamler and coworkers in 1996 (Jia et al., 1996 Stamler et al., 1997). To this day HbSNO remains controversial with respect to its mechanism of formation and physiological relevance. 

Pharmacology Iron is essential to the synthesis of hemoglobin to maintain oxygen transport and to the function and formation of other physiologically important heme and nonheme compounds. 

AUTOMATED INSTRUMENTATION HEMATOLOGY. Hematology analyzers provide information about blood cells and their constituents. The three basic blood cell types are erythrocytes or red blood cells, leukocytes or white blood cells, and thrombocytes or platelets. Hemoglobin is die principal nonaqueous component of red blood cells. Its physiological importance gives it the status of a primary hematological constituent. 

Nonmetal oxides dissolve in water to give acid solutions. The most physiologically important example is carbon dioxide. Of course, you already know this. Buildup of carbon dioxide in the blood results in acidosis. This is not necessarily a bad thing. In cellular tissue, where the carbon dioxide concentration is relatively high, the increased acidity slightly alters the structure of hemoglobin, and facilitates the release of oxygen. 

Diphosphoglycerate (2,3-DPG) is an important mediator of hemoglobin physiology (see Chapter 7). It is synthesized from 1,3-diphosphoglycerate. The... 

Owing to its physiological importance the oxygenation-deoxygenation process in hemoglobin has been widely investigated, but it is beyond the purposes of the present paper to give an account of the studies so far reported (see e.g. Ref. 127 for recent reviews), except for some main aspects. 

The Bohr effect, i.e., the uptake of hydrogen ions above pH 6 (known as the alkaline Bohr effect), is physiologically important because the ions released on uptake of CO2 by the blood from the tissues are neutralized through this mechanism. Figure 4 illustrates the Bohr effect of normal hemoglobin the reverse effect, the acid Bohr effect, has no physiological significance because it is observed below pH 6. 

In hemoglobin, the interactions between the subunits are known under the general term of allosteric properties and are of great physiological importance. They determine the cooperative binding of O2. In the deoxy form, the iron atom of each heme is in a high-spin (S =2) five-coordinate iron(II) state and lies about 0.5 A out of the heme plane in the direction of the proximal histidine [12]. The Fe-N(imida2ole) bond vector has 10° tilt off the heme normal. 

Erythrocytes are subjected to a continuous flux of 02 and H202 due to hemoglobin autooxidation (C3,H9,M26,W3) and also undergo oxidative stress from environmental agents (C6). Cu,Zn-SOD in the erythrocytes may have some physiologically important role in combating these processes. 

AAThen oxygen is attached to hemoglobin in neutral solution, the pH of the solution is lowered (the Bohr effect). This phenomenon is of great physiological importance for the transport of carbon dioxide in the blood. 

The transition between the T and R states of hemoglobin is also deeply involved in the Bohr effect and cooperativity. Therefore stabilization of either of the two stmctures should diminish these effects, which have important physiologic consequences. The clinical consequences of stabilization are not known. 

We can determine quantitatively the physiological significance of the sigmoid nature of the hemoglobin oxygen-binding curve, or, in other words, the biological importance of cooperativity. The equation... 

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