Preparation of myoglobins.

Publisher Summary This chapter presents procedures for the isolation of intracellular oxygen-binding proteins of tissues, called “tissue hemoglobins” in the widest sense. All of these, except Ascaris and yeast hemoglobin, are monomers or dimers having a minimum molecular weight of 18,000 with similar optical spectra and chemical reactivity. Strictly, only muscle hemoglobin should be called “myoglobin”; by extension the term is often applied to other tissue hemoglobins as well. Ferric myoglobin may be purified by chromatography on carboxymethyl (CM) cellulose, usually at slightly acid pH or on diethylaminoethyl (DEAE) cellulose. The choice of preparative procedure depends on the use to which the purified myoglobin will be put. Both DEAE and CM ion-exchange columns yield myoglobin that is pure in the sense of being free from contaminating polypeptide chains. Better resolution of forms of myoglobin differing only in charge is achieved on CM-cellulose. Such columns, however, are usually operated at acid pH, and it is a matter of experience that oxymyoglobin exposed to mildly acidic conditions becomes ferric and, in the process, undergoes some minor but apparently irreversible change. The chapter also explains the isolation and purification of vertebrate myoglobins.