Kowalik Bartosz, Schubert Thomas, Wada Hirofumi, Tanaka Motomu, Netz Roland R, Schneck Emanuel
Fachbereich Physik, Freie Universität Berlin , D-14195 Berlin, Germany.
Institute of Physical Chemistry, Heidelberg University , D-69120 Heidelberg, Germany.
J Phys Chem B. 2015 Nov 5;119(44):14157-67. doi: 10.1021/acs.jpcb.5b05501. Epub 2015 Oct 22.
The phase behavior of membrane lipids plays an important role in the formation of functional domains in biological membranes and crucially affects molecular transport through lipid layers, for instance, in the skin. We investigate the thermotropic chain melting transition from the ordered Lβ phase to the disordered Lα phase in membranes composed of dipalmitoylphosphatidylcholine (DPPC) by atomistic molecular dynamics simulations in which the membranes are subject to variable heating rates. We find that the transition is initiated by a localized nucleus and followed by the propagation of the phase boundary. A two-state kinetic rate model allows characterizing the transition state in terms of thermodynamic quantities such as transition state enthalpy and entropy. The extrapolated equilibrium melting temperature increases with reduced membrane hydration and thus in tendency reproduces the experimentally observed dependence on dehydrating osmotic stress.
膜脂的相行为在生物膜功能域的形成中起着重要作用，并对分子通过脂质层的运输产生关键影响，例如在皮肤中。我们通过原子分子动力学模拟研究了由二棕榈酰磷脂酰胆碱（DPPC）组成的膜中从有序Lβ相到无序Lα相的热致链熔化转变，其中膜承受可变的加热速率。我们发现，转变由一个局部核引发，随后是相边界的传播。一个双态动力学速率模型允许根据诸如过渡态焓和熵等热力学量来表征过渡态。外推的平衡熔化温度随着膜水合作用的降低而升高，因此在趋势上再现了实验观察到的对脱水渗透应力的依赖性。
