Retention of bacteriorhodopsin activity in dried sol-gel glass

The D96N mutant form of bacteriorhodopsin (bR) purple membrane fragments isolated from Halobacterium salinarium has been entrapped in sol-gel glass and dried. The photo-activity of the bR was monitored during drying over a period of 60 days. The entrapped bR was initially dried at 4 degrees C followed by room temperature storage. Samples showing constant activity after storage at 4 degrees C lost further activity at room temperature, eventually reaching a level where the activity remained constant. Upon further drying at 100 degrees in a vacuum oven the glass lost an additional 11.4 +/- 1.3% weight and all remaining activity.