Potekhin Sergey A, Senin Alexander A, Abdurakhmanov Nickolay N, Khusainova Railya S
Institute of Protein Research, Russian Academy of Sciences, Moscow Region, Russia.
Biochim Biophys Acta. 2011 Jul;1808(7):1806-10. doi: 10.1016/j.bbamem.2011.02.020. Epub 2011 Mar 4.
The bilayer phase transitions from the ripple gel phase (P'(β)) to the liquid-crystal phase (L(α)) of a series of 1,2-diacylphosphatidylcholines containing a linear saturated acyl chain (C=14-19) have been studied by high-pressure scanning microcalorimetry. It has been shown that at ambient pressure, the transition temperature increases non-linearly depending on the acyl chain length. Pressure stabilizes the gel phase of lipids in a similar way; the pressure derivatives of the logarithm transition temperature as function of pressure are identical for all lipids. Based on the results obtained it has been concluded that the ratio γ of volume to enthalpy increments upon transitions in 1,2-diacylphosphatidylcholines is not dependent on the acyl chain length. When pressure grows, this ratio decreases drastically remaining identical for all lipids studied. Besides it has been demonstrated that increments of coefficients of thermal expansibility and isothermal compressibility are also rigidly bound to each other. Semi-empirical equations permitting to estimate volume parameters of the gel-to-liquid transition for 1,2-diacylphosphatidylcholines are given. The reasons for invariance of γ are discussed.
利用高压扫描量热法研究了一系列含有直链饱和酰基链（C = 14 - 19）的1,2 - 二酰基磷脂酰胆碱从波纹凝胶相（P'(β)）到液晶相（L(α)）的双层相变。结果表明，在环境压力下，转变温度随酰基链长度呈非线性增加。压力以类似方式稳定脂质的凝胶相；所有脂质的对数转变温度随压力的导数相同。基于所得结果得出结论，1,2 - 二酰基磷脂酰胆碱转变时体积与焓增量之比γ不依赖于酰基链长度。当压力增加时，该比值急剧下降，且对于所有研究的脂质保持相同。此外，已证明热膨胀系数和等温压缩系数的增量也紧密相关。给出了用于估算1,2 - 二酰基磷脂酰胆碱凝胶 - 液相转变体积参数的半经验方程。讨论了γ不变的原因。
