"Mechanics of Cells and Tissues in Diseases” Vol 2.

The red blood cells contain significant concentrations (millimolar range) of he- moglobin (Hb), a very much investigated tetrameric protein (Antonini and Brunori, 1970) that contains heme-iron and is capable of cooperative and reversible binding of molecular oxygen and carbon dioxide, enabling their transport from the lungs to the peripheral tissues, and vice versa. In addition to this main physiological func- tion, a variety of secondary roles, mostly regulative, has been suggested for Hb (Giardina et al., 1995). The presence of the cellular microenvironment is certainly very important in the protection of the structural and functional integrity of Hb as well as in the control of the protein’s activity, especially with regard to the oxida- tion state of iron and the role of allosteric effectors. Besides this protective role, however, the main cell function of O2/CO2 shuttle induces several important conse- quences on the structural and cellular biology of the erythrocytes that makes these cells somehow unique in the body. In the next paragraph we will briefly recall a few important characteristics of the red cells that will clarify the correlation be- tween their morphology, structure, and function, and will properly highlight the importance of studying their mechanical properties.