Vagenende Vincent, Ching Tim-Jang, Chua Rui-Jing, Jiang Qiu Zhen, Gagnon Pete
Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), 20 Biopolis Way #06-01 Centros, Singapore 138668, Singapore.
Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), 20 Biopolis Way #06-01 Centros, Singapore 138668, Singapore.
Colloids Surf B Biointerfaces. 2014 Aug 1;120:8-14. doi: 10.1016/j.colsurfb.2014.04.008. Epub 2014 May 23.
Self-assembly of lipopolysaccharides (LPS) on solid surfaces is important for the study of bacterial membranes, but has not been possible due to technical difficulties and the lack of suitable solid supports. Recently we found that crystals of the natural compound allantoin selectively bind pure LPS with sub-nanomolar affinity. The physicochemical origins of this selectivity and the adsorption mode of LPS on allantoin crystals remain, however, unknown. In this study we present evidence that LPS adsorption on allantoin crystals is initiated through hydrogen-bond attachment of hydrophilic LPS regions. Hydrophobic interactions between alkyl chains of adjacently adsorbed LPS molecules subsequently promote self-assembly of LPS layers. The essential role of hydrogen-bond interactions is corroborated by our finding that allantoin crystals bind to practically any hydrophilic surface chemistry. Binding contributions of hydrophobic interactions between LPS alkyl chains are evidenced by the endothermic nature of the adsorption process and explain why the binding affinity for LPS is several orders of magnitude higher than for proteins (lysozyme, BSA and IgG) and polysaccharides. Self-assembly of LPS layers via hydrogen-bond attachment on allantoin crystals emerges as a novel binding mechanism and could be considered as a practical method for preparing biomimetic membranes on a solid support.
脂多糖（LPS）在固体表面的自组装对于细菌膜的研究很重要，但由于技术困难和缺乏合适的固体支持物，一直无法实现。最近我们发现，天然化合物尿囊素的晶体以亚纳摩尔亲和力选择性结合纯LPS。然而，这种选择性的物理化学起源以及LPS在尿囊素晶体上的吸附模式仍然未知。在本研究中，我们提供证据表明，LPS在尿囊素晶体上的吸附是通过亲水性LPS区域的氢键连接启动的。相邻吸附的LPS分子的烷基链之间的疏水相互作用随后促进了LPS层的自组装。我们发现尿囊素晶体与几乎任何亲水性表面化学物质结合，这证实了氢键相互作用的重要作用。吸附过程的吸热性质证明了LPS烷基链之间疏水相互作用的结合贡献，并解释了为什么对LPS的结合亲和力比对蛋白质（溶菌酶、牛血清白蛋白和免疫球蛋白）和多糖高几个数量级。通过氢键连接在尿囊素晶体上自组装LPS层是一种新的结合机制，可被视为在固体支持物上制备仿生膜的实用方法。
