The relationship between the membrane bending modulus (κ) and compressibility modulus (KA) depends on the extent of coupling between the two monolayers (leaflets). Using neutron spin echo (NSE) spectroscopy, we investigate the effects of n-alkanes on the interleaflet coupling of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers. Structural studies with small-angle X-ray and neutron scattering (SAXS and SANS) showed that the bilayer thickness increased with increasing n-alkane length, while NSE suggested that the bilayers became softer. Additional measurements of the membrane thickness fluctuations with NSE suggested that the changes in elastic moduli were due to a decrease in coupling between the leaflets upon addition of the longer n-alkanes. The decreased coupling with elongating n-alkane length was explained based on the n-alkane distribution within the bilayers characterized by SANS measurement of bilayers composed of protiated DPPC and deuterated n-alkanes. A higher fraction of the incorporated long n-alkanes were concentrated at the central plane of the bilayers and decreased the physical interaction between the leaflets. Using NSE and SANS, we successfully correlated changes in the mesoscopic collective dynamics and microscopic membrane structure upon incorporation of n-alkanes.

中文翻译：

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正构烷烃结合双层的叶间偶联。

膜弯曲模量（κ）和可压缩模量（KA）之间的关系取决于两个单层（小叶）之间的偶联程度。使用中子自旋回波（NSE）光谱，我们研究了正构烷烃对1,2-二棕榈酰-sn-甘油-3-磷酸胆碱（DPPC）双层的叶间偶联的影响。用小角度X射线和中子散射（SAXS和SANS）进行的结构研究表明，随着正构烷烃长度的增加，双层膜的厚度会增加，而NSE则表明双层膜会变得更软。用NSE进行的膜厚度波动的其他测量结果表明，弹性模量的变化是由于在加入更长的正构烷烃后，小叶之间的耦合降低了。基于双层内的正构烷烃分布，解释了随着正构烷烃长度的增加而降低的偶联，其特征在于通过SANS测量由多官能DPPC和氘代正构烷烃组成的双层结构。较高比例的掺入的长正构烷烃集中在双层的中心平面，并降低了小叶之间的物理相互作用。使用NSE和SANS，我们成功地结合了正构烷烃后介观集体动力学和微观膜结构的变化。