反式脂肪酸被發現在含有脂肪或油的食品中，特別是通過部分氫化、除臭或高溫油炸等處理過程的加工食品，並且反式脂肪酸也已被發現存在於人體脂肪組織。攝取反式脂肪酸被認為是對健康有害的危險因素，如關聯至冠狀動脈疾病和造成心臟疾病的風險等。在這項研究中，我們進行了長時間尺度的全原子分子動態模擬，探討順式單元不飽和脂質POPC(1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) 與反式單元不飽和脂質PEPC(1-palmitoyl-2-elaidoyl-sn-glycero-3-phosphocholine) 這兩種脂質膜系統，以及POPC和PEPC脂質的混合膜系統，不同雙鍵構型在結構和動態性質上造成的影響。我們從模擬中發現順式或反式雙鍵的幾何構型，可以改變鄰近雙鍵的兩個扭轉角的構型和動態，不同於碳鏈上其他飽和的扭轉角。PEPC脂質結構上相鄰反式雙鍵的兩個扭轉角，主要是採取非平面的skew-trans 構型模組和平面的cis-trans構型模組；POPC脂質結構上相鄰順式雙鍵的兩個扭轉角，卻是主要採取非平面的skew-trans和skew-gauche構型模組。然而POPC和PEPC在相鄰雙鍵的兩個扭轉角擁有相似的動態性質：比起碳鏈上其他飽和的扭轉角，第一鄰近雙鍵的扭轉角有較快的旋轉運動，相反的是第二鄰近的扭轉角卻有較慢的旋轉運動。與POPC脂質相比較，PEPC脂質擁有較佳的膜堆疊，因此導致比較小的平均頭基面積，與比較高的碳鏈秩序參數，以及比較小的擴散係數。POPC與PEPC脂質間獨特的性質差異，使得在以POPC為基質的系統內，PEPC能夠聚集形成脂質域。

Trans fatty acid isomers have been identified in the foods containing fats and oils, which were particularly processed through the partial hydrogenation, deodorization or frying at high temperatures and have been found to present in human adipose tissue. The trans fatty acid isomers have also been identified to link with some harmful health effects such as coronary artery diseases and risk factors of heart attack. In this study, we performed long time-scale MD simulations using all-atom force field to investigate the structure and dynamics properties of mono-cis-unsaturated POPC(1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and mono-trans-unsaturated PEPC(1-palmitoyl-2-elaidoyl-sn-glycero-3-phosphocholine) lipids as well as the mixed systems of POPC and PEPC lipids. Our simulations found the geometry of the (cis or trans) double bond can alter the conformations and dynamics of the two torsion angles next to the double bond from those of saturated torsion angles. The two torsion angles of the PEPC lipids next to the double bond mainly adopt a non-planar skew-trans and planar cis-trans motifs; the POPC lipids mainly adopt a non-planar skew-trans and skew-gauche motifs. POPC and PEPC lipids have similar dynamical properties of the two torsion angles next to the double bond: first torsion angles have fast rotational motions and in contrast, the second torsion angles have slower rotational motions than those of saturated torsion angles. PEPC lipids have better packing than POPC lipids leading to smaller area per lipid, higher order parameter, and smaller diffusion coefficient. The distinct properties of POPC and PEPC lipids allow PEPC lipids to form domain within POPC matrix.

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