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Proteins are the major macromolecules in the living system being responsible for all processes of life including respiration, digestion, growth and reproduction, defense, visualization, signal transduction and cellular communication etc. Hemocyanins are oxyphoric blue copper-containing respiratory proteins present in the hemolymph of many species of arthropod and mollusc. Scorpion hemocyanin is composed of 24 monomeric subunits assembled in four hexameric blocks. It contains eight different types of polypeptide chains present in two or four copies within the native molecule. The first chapter describes a detailed overview of oxygen transport proteins, their distribution and evolution, and structure-function relationship with special emphasis on hemocyanins, the blue blood. The modern experimental techniques used have been precisely described in chapter two. Results of studies on scorpion hemocyanin are presented in chapter three which is followed by a detailed comparison with other arthropod hemocyanins and discussed in chapter four. A fully up to date literature support with over 250 citations on the subject are aligned alphabetically in chapter five for quick reference.

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