Rational design of lipid molecular structure:: A case study involving the C19:1c10 monoacylglycerol

The phase properties of lipids have far-reaching consequences in membrane biology. Their influence ranges from domain formation in intact biomembranes to membrane protein reconstitution and crystallization. To exploit phase behavior in the spirit of rational design, it is imperative that the rules relating lipid molecular structure and liquid crystal or mesophase behavior be established. Phase behavior is quantitatively and concisely represented in the form of temperature-composition phase diagrams. A somewhat limited number of phase diagrams exists for the monoacylglycerols. The objective of the current study was to determine the quality of phase behavior prediction for a specific monoacylglycerol based on an analysis of the existing phase diagrams for related chain homologs. To this end, a phase diagram for the monononadecenoin (19:1c10)/water system was predicted in the temperature range from -15 degreesC to 120 degreesC and from 0% to 80% (w/w) water. The prediction was tested by constructing the corresponding phase diagram using low- and wide-angle x-ray diffraction, differential scanning calorimetry, and polarized light microscopy. The results show that the predicted and experimental phase diagrams agree remarkably well. They also highlight the need for additional phase studies of the type described to enlarge the data bank of phase diagrams and to strengthen the foundations of the rational design approach.