Myoglobins isoelectric point

The enthalpy of ionization of the titratable histidine groups in myoglobin is 7.5 kcal mol-1 (Antonini and Brunori, 1971). These groups are involved at the isoelectric point level. The solvent effect on the pKa of histidine has been measured. From a value of 6.1 in pure water, it decreases to 5.85 in the mixed solvent, at +20°C. The conditions (AH buffer > AH of the pi) for isoelectric focusing are therefore satisfied. 

The proteins ovalbumin (isoelectric point pi = 4.6), urease (pi = 5.0), and myoglobin (pi = 7.0) were added to a column of the anion-exchange resin, DEAE-cellulose at pH 6.5. The column was eluted with a dilute pH 6.5 buffer and then with the same buffer as a gradient, containing an increasing concentration of NaCl. In what order will the proteins be eluted from the column ... 

Myoglobins. Distribution. Function. Molecular weight. Isoelectric points. Solubili. Composition. 

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