For some reason, recently we are facing some quenching problem in our tagged SLBs. For the same conditions(dye concentration, laser power etc.,) we have used before, intensity from the bilayer appears drastically low. Also the DMPC, DLPC bilayer  behaves more gel like unlike our earlier experiments.

SLBs are prepared using LB technique for confocal based measurements.I am not able to figure out the reason for this problem. As I now tried different lipids and different fluorescent probe as well to overcome this.

Isotherm of the transferred lipids looks perfect.Transfer ratios are also good. 

Have you come across such an issue?