Department of Chemical Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain.
J Colloid Interface Sci. 2012 Oct 15;384(1):189-97. doi: 10.1016/j.jcis.2012.06.066. Epub 2012 Jul 4.
Ubiquinone and plastoquinone are two of the main electron and proton shuttle molecules in biological systems, and monogalactosyldiacylglycerol (MGDG) is the most abundant lipid in the thylakoid membrane of chloroplasts. Saturated MGDG, ubiquinone-10 (UQ) and MGDG:UQ mixed monolayers at the air/water interface have been studied using surface pressure-area isotherms and Brewster Angle Microscopy. Moreover, the transferred Langmuir-Blodgett films have been observed by Atomic Force Microscopy. The results show that MGDG:UQ mixtures present more fluid phase than pure MGDG, indicating a higher order degree for the later. It is also observed an important influence of UQ on the MGDG matrix before UQ collapse pressure and a low influence after this event, due to UQ expulsion from the MGDG matrix. This expulsion leads to a similar remaining UQ content for all the tested mixtures, indicating a limiting content of this molecule in the MGDG matrix at high surface pressures. The thermodynamic studies confirm the stability of the MGDG:UQ mixtures at low surface pressures, although presenting a non-ideal behaviour. Results point to consider UQ as a good candidate for studies of artificial photosynthesis.
泛醌和质体醌是生物系统中主要的电子和质子穿梭分子，而单半乳糖二酰基甘油（MGDG）是叶绿体类囊体膜中最丰富的脂质。使用表面压-面积等温线和布鲁斯特角显微镜研究了饱和 MGDG、泛醌-10（UQ）和 MGDG:UQ 混合单层在空气/水界面上的性质。此外，还通过原子力显微镜观察了转移的 Langmuir-Blodgett 膜。结果表明，MGDG:UQ 混合物比纯 MGDG 具有更多的流体相，表明后者具有更高的有序度。还观察到 UQ 在 UQ 坍塌压力之前对 MGDG 基质有重要影响，而在此事件之后影响较小，这是由于 UQ 从 MGDG 基质中排出。这种排出导致所有测试混合物的剩余 UQ 含量相似，表明在高表面压力下，该分子在 MGDG 基质中的含量有限。热力学研究证实了 MGDG:UQ 混合物在低表面压力下的稳定性，尽管表现出非理想行为。结果表明，UQ 可以作为人工光合作用研究的良好候选物。
