リン脂質二分子膜は温度，圧力，塩濃度などの環境因子に依存し，様々な相転移を起こす。脂質二分子膜相転移の検出には示差走査熱量測定が特に効果的であるが，それらの熱的情報を圧力測定から得られた結果と組み合わせることで脂質二分子膜相転移の熱力学理解を深めることが可能となる。生体膜研究において繁用されているリン脂質が形成する二分子膜の相転移を解説し，高圧下における相転移測定を紹介した。続いて疎水鎖種類（アシル鎖の不飽和度）および極性基サイズの異なるホスファチジルエタノールアミン同族体における二分子膜相転移を取り上げ，相転移温度の圧力依存性，温度－圧力相図および相転移に伴う熱力学量変化を用いてこれら脂質二分子膜の相転移を熱力学的に特徴づけた。
Phospholipid bilayer membranes undergo various phase transitions depending on environmental factors such as temperature, pressure, salt concentration and so on. Although the differential scanning calorimetry (DSC) is especially effective in detecting the bilayer phase transitions, combination of the thermal information with results obtained from pressure measurements enables us to deepen a thermodynamic understanding of the bilayer transitions. Phase transitions of bilayer membranes formed by phospholipids, which are frequently used in studies of biological membranes, were explained and phase transition measurements under high pressure were introduced. Next the bilayer phase transitions for phosphatidylethanolamine homologues with different kinds of hydrophobic chains (degree of unsaturation in acyl chains) and different-sized polar head groups were taken up and the bilayer phase transitions were thermodynamically characterized in terms of pressure dependence of phase-transition temperatures, temperature-pressure phase diagrams and thermodynamic quantity changes associated with phase transitions.
