Iodide fluorescence quenching of sol-gel immobilized BSA

Several potential applications of sol-gel immobilized proteins may require drying the gel before use. The attendant shrinkage may sterically restrict the penetration of solutes to the entrapped protein. In this study, collisional quenching of intrinsic bovine serum albumin (BSA) fluorescence by dissolved iodide was used to quantitatively compare the accessibility of protein molecules entrapped in hydrated and dried sol-gel monoliths. The results show that iodide penetration to immobilized BSA is sterically restricted by approximately 25% in hydrated gels and 50% in dried gels, relative to the quenching behavior of dissolved BSA. The further decrease upon drying is consistent with the overall degree of monolith shrinkage.