This membrane phenomenon greatly in creased the efficiency of the CLI protocol, as many membranes could be processed in the same reaction chamber without antigen cross-contamination between the membranes. Because the PVDF membranes were easy to use, were much more durable than the nitrocellulose membranes, and had better color re- tention than the Zeta-Probe membranes, the PVDF mem- branes were used for optimizing the CLI procedure.