An improved technique for preparing polycationic ferritin derivatives.

Cationized ferritin molecules, which are positively charged at physiological pH, can be used as a cytochemical marker to visualize negatively charged groups over cell surfaces. The preparation of cationized ferritin, however, is hampered by irreversible aggregation of the ferritins and by poor reproducibility of pI values. In this report we describe an improved method which allows production of ferritin derivatives with different pI values. An elaborate protocol for the preparation of cationized ferritin is given as well as a table for the adjustment of their pI values to between 4.5--10.0.