Controlling the Extent of Reactions With Enzyme-Containing Membranes

Membrane reactors present unique opportunities for controlling residence times on the msec scale and providing high local catalyst concentrations.   This presentation focuses on protein digestion in membranes containing immobilized enzymes.  For first-order reactions, simple kinetic arguments show that the time required for a given extent of reaction in the entire volume is the same in solution or in the membrane when using the same amount of enzyme in both systems.  However, the membrane provides much better control over the extent of reaction.  This is particularly important for controlling peptide sizes during protein digestion for subsequent mass spectrometric analysis.  With short residence times (from ms to s), proteolysis occurs only at the most accessible and reactive sites on the substrate protein.  Increased flow rates lead to larger peptides and enhanced sequence coverages that are important for examining protein modifications or sequencing unknown proteins such as antibodies.  Immobilization of enzymes also facilitates their reuse.  The presentation will also examine the removal of protein tags that facilitate purification.