2.1. GLOBIN GENES AND HEMOGLOBIN
Native hemoglobin exists as a tetrameric protein consisting of two .alpha. chains and two .beta. chains. Each .alpha. and .beta. chain binds a heme residue in noncovalent linkage. The .alpha. and .beta. chains are also held together by noncovalent bonds resulting from hydrogen bonding and Van der Waals forces. Hemoglobin constitutes about 90% of the total protein in red blood cells; 100 ml of whole blood is capable of absorbing approximately 21 ml of gaseous oxygen.