2-modified 1,3-diacylglycerols as new surfactants for the formation of reverse micelles

New 2-modified 1,3-diacylglycerols such as 1,3-dilauroylglycerol 2-disodiumphosphate and analogues were characterized with respect to their tendency to form reverse micelles in isooctane and isooctane/1-hexanol. The water content of the reverse micelles was determined by Karl-Fischer titration. The critical micelle concentration of the compounds was estimated by fluorescence measurements using rhodamine B as indicator. The concentration regions where reverse micelles are observed were characterized by pseudoternary phase diagrams. The ability of the surfactants to extract proteins into the organic phase was examined for cytochrome c. The properties of the new compounds were compared with the behaviour of the corresponding regioisomeric 3-modified 1,2-diacylglycerols as well as lecithin and the surfactant AOT, which is preferably used for the formation of reverse micelles. The results suggest that the position of the head group in the modified diacylglycerols is of low importance for the phase behaviour whereas the ability to form reverse micelles decisively depends on the kind of the head group.