Copper-zinc superoxide dismutase (CuZnSOD), myoglobin, hemoglobin and glucose oxidase are encapsulated in stable, optically transparent, porous, silica glass matrices synthesized under mild conditions using novel sol-gel synthetic techniques. The biomolecules retain their characteristic reactivities and spectroscopic properties. The porous glasses allow transport of small molecules into and out of the glasses at reasonable rates but retain the protein molecules within the pores. The chemical reactions of the immobilized proteins are monitored by means of changes in their visible absorption spectra. Four encapsulated proteins are studied: CuZnSOD reacts with CN−; metmyoglobin is reduced to its deoxy form and then reacts with O2 to make the oxy form and CO to make the carbonyl form; methemoglobin is reduced to its deoxy form and reacted with CO to make the carbonyl form; and glucose oxidase is reacted with glucose to make gluconic acid.