Turner D C, Gruner S M, Huang J S
Department of Physics, Joseph Henry Laboratories, Princeton University, New Jersey 08544.
Biochemistry. 1992 Feb 11;31(5):1356-63. doi: 10.1021/bi00120a010.
The addition of a free alkane such as decane to lipid-water systems is known to promote the formation of a low-temperature inverted hexagonal (HII) phase [Kirk, G. L., & Gruner, S. M. (1985) J. Phys. (Paris) 46, 761]. Kirk et al. [Kirk, G. L., Gruner, S. M., & Stein, D. E. (1984) Biochemistry 23, 1093] have discussed the hydrocarbon packing anisotropy in the HII unit cell and have suggested that free alkane will distribute in a way that reduces this packing anisotropy by allowing the lipid chain environment to become more uniform. By combining neutron and X-ray diffraction data to do a Fourier reconstruction of the HII phase of dioleoylphosphatidylethanolamine (DOPE) + water + deuterated decane, it was found that the decane preferentially partitions into the interstitial regions of the HII unit cell where it should be the most effective in alleviating the hydrocarbon chain packing stress, supporting the suggestion of Kirk et al. Using the distribution of decane within the unit cell, we have calculated the lipid length distribution for the situations with and without added alkane. With a suitable molecular model, this lipid length distribution may eventually be used to calculate the free energy change upon the addition of alkane. Such a measurement is important for a more realistic understanding of the interactions which lead to the formation of the HII phase.
已知在脂质 - 水体系中添加癸烷等游离烷烃可促进低温反相六角（HII）相的形成[柯克，G. L.，& 格鲁纳，S. M.（1985）《法国物理杂志》46，761]。柯克等人[柯克，G. L.，格鲁纳，S. M.，& 斯坦，D. E.（1984）《生物化学》23，1093]讨论了HII晶胞中的烃堆积各向异性，并提出游离烷烃将以一种通过使脂质链环境变得更均匀来降低这种堆积各向异性的方式分布。通过结合中子和X射线衍射数据对二油酰磷脂酰乙醇胺（DOPE）+水+氘代癸烷的HII相进行傅里叶重建，发现癸烷优先分配到HII晶胞的间隙区域，在那里它在减轻烃链堆积应力方面应该是最有效的，这支持了柯克等人的观点。利用癸烷在晶胞内的分布，我们计算了添加和不添加烷烃情况下的脂质长度分布。通过合适的分子模型，这种脂质长度分布最终可用于计算添加烷烃时的自由能变化。这样的测量对于更实际地理解导致HII相形成的相互作用很重要。
