松木均先生らの論文「Bilayer phase transitions of dipalmitoylphosphatidic acid: Effect of the absence of a polar head group」が掲載されました。

 

掲載誌等：Thermochimica Acta, 759, 180273, 2026.
DOI：10.1016/j.tca.2026.180273
著者：Kana Kajiura, Sohta Matsuoka, Kaori Kubo, Suzuno Konishi, Masaki GOTO, Nobutake Tamai and Hitoshi Matsuki

 

要約：The thermotropic and barotropic phase transitions of bilayers formed by dipalmitoylphosphatidic acid (DPPA), an acidic phospholipid lacking a polar head group, were investigated by complementary calorimetric and high-pressure optical measurements in the absence and presence of added salt (NaCl) to clarify the role of polar head groups in membrane phase behavior. The phase behavior depended strongly on the annealing temperature. Samples prepared in the liquid-crystalline phase exhibited a transition from a metastable hydrated crystalline phase to the gel phase, followed by the chain-melting (main) transition, whereas samples prepared in the gel phase showed a transition from a stable hydrated crystalline phase to the gel phase and the main transition. At NaCl concentrations of 0.3 mol kg⁻¹ or lower, a thermal history–dependent gel–gel transition was observed. Temperature–pressure phase diagrams showed that transitions involving hydrated crystalline phases and the main transition shifted to higher temperatures with increasing pressure, whereas the gel–gel transition shifted to lower temperature, exhibiting a negative pressure dependence. This anomalous pressure dependence provides direct thermodynamic evidence that the high-temperature gel phase corresponds to an interdigitated structure even in the absence of added salt. This finding provides new insight into how the absence of a polar head group fundamentally alters bilayer packing and phase stability in acidic phospholipid membranes. Comparison with bilayers of dipalmitoylphosphatidylglycerol (DPPG), an acidic phospholipid possessing a polar head group, revealed pronounced differences in transition temperatures, phase stability, and salt dependence, attributable to closer counter-ion approach to the exposed phosphate group in DPPA.

 

キーワード：酸性リン脂質 / 二分子膜 / 示差走査熱量測定 / 高圧力 (high pressure) / 相転移 (phase transition)