Lyophilisation of thylakoids: A tool for long-term stability of the biological unit

The lyophilisation of thylakoids, used as biological units to determine her bicides in water and soil, is described. Cryoprotectives as bovine serum al bumine (2 %) and sucrose (200-400 mM) proved to be efficient additives to o ptimise the final activity of the thylakoids after lyophilisation. The acti vity was maintained between 87-99 % relative to the activity directly after isolation. Long term storage of freeze-dried thylakoids was simulated with different temperature conditions. Comparison of non lyophilised with lyoph ilised thylakoids showed the advantage of the conservation method under sim ulated transport conditions; the cooling of lyophilised thylakoids can be i nterrupted without high decrease in activity. Therefore the lyophilisation of thylakoids allows a continuous, reproducible supply of the photosyntheti c active unit for each application of the bioassay.