ORGANIZATION OF BIPOLAR LIPIDS IN MONOLAYERS AT THE AIR-WATER-INTERFACE

In this paper we report the results of surface pressure-area measureme nts and fluorescence microscopy of Langmuir monolayers of bipolar lipi ds extracted from the thermophilic archaeobacterium Sulfolobus solfata ricus. We have analysed the two-dimensional phase behaviour of the pol ar lipid extract, some of its subfractions and the hydrolytic fraction s glycerol dialkyl glycerol tetraether (GDGT) and glycerol dialkyl non itol tetraether (GDNT) in the temperature range 25-45-degrees-C. For c omparison, films of diphytanoyl phosphatidylcholine were also studied. Only the isotherms of the polar lipid extract exhibit a plateau regio n. The molecular areas of GDGT and GDNT, even at the collapse pressure , are much larger than those of the other lipid fractions. For the for mer compounds a U-shaped hydrocarbon chain conformation mixed with an extended chain arrangement is suggested, while all the other fractions display always a vertical arrangement.