Abou-Zied Osama K, Zahid N Idayu, Khyasudeen M Faisal, Giera David S, Thimm Julian C, Hashim Rauzah
Department of Chemistry, Faculty of Science, Sultan Qaboos University, P.O. Box 36, Postal Code 123, Muscat, Sultanate of Oman.
Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
Sci Rep. 2015 Mar 3;5:8699. doi: 10.1038/srep08699.
Local heterogeneity in lipid self-assembly is important for executing the cellular membrane functions. In this work, we chemically modified 2-(2'-hydroxyphenyl)benzoxazole (HBO) and attached a C8 alkyl chain in two different locations to probe the microscopic environment of four lipidic phases of dodecyl β-maltoside. The fluorescence change in HBO and the new probes (HBO-1 and HBO-2) shows that in all phases (micellar, hexagonal, cubic and lamellar) three HBO tautomeric species (solvated syn-enol, anionic, and closed syn-keto) are stable. The formation of multi tautomers reflects the heterogeneity of the lipidic phases. The results indicate that HBO and HBO-1 reside in a similar location within the head group region, whereas HBO-2 is slightly pushed away from the sugar-dominated area. The stability of the solvated syn-enol tautomer is due to the formation of a hydrogen bond between the OH group of the HBO moiety and an adjacent oxygen atom of a sugar unit. The detected HBO anions was proposed to be a consequence of this solvation effect where a hydrogen ion abstraction by the sugar units is enhanced. Our results point to a degree of local heterogeneity and ionization ability in the head group region as a consequence of the sugar amphoterism.
脂质自组装中的局部异质性对于执行细胞膜功能至关重要。在这项工作中，我们对2-(2'-羟基苯基)苯并恶唑（HBO）进行了化学修饰，并在两个不同位置连接了一条C8烷基链，以探究十二烷基β-麦芽糖苷四种脂质相的微观环境。HBO以及新探针（HBO-1和HBO-2）的荧光变化表明，在所有相（胶束相、六方相、立方相和层状相）中，三种HBO互变异构体（溶剂化顺式烯醇、阴离子型和封闭顺式酮型）都是稳定的。多种互变异构体的形成反映了脂质相的异质性。结果表明，HBO和HBO-1位于头基区域内的相似位置，而HBO-2则被稍微推离了以糖为主的区域。溶剂化顺式烯醇互变异构体的稳定性归因于HBO部分的OH基团与糖单元的相邻氧原子之间形成了氢键。检测到的HBO阴离子被认为是这种溶剂化效应的结果，在这种效应下，糖单元对氢离子的夺取增强。我们的结果表明，由于糖的两性性质，头基区域存在一定程度的局部异质性和电离能力。
