無機鹽類與卵磷脂在有機溶劑中的作用力與其對自組裝行為的影響

Interactions between lecithin and inorganic salts in oil and their effects on the reverse micellization

林詩婷(Shih-Ting Lin)

指導教授 ： 童世煌

國立臺灣大學/工學院/高分子科學與工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.02613

摘要

生物界面活性劑在人體中扮演重要的角色，卵磷脂為人體內最常見的生物界面活性劑之一，且是細胞膜最主要的成分。而存在於我們人體內的無機鹽類，雖然含量不多，但無機鹽類卻是調節人體生理機能的關鍵成分。卵磷脂與無機鹽類之間的交互作用一直是一個重要的研究課題，由於在水溶液中受到大量水分子的干擾，而較難得知磷脂質與不同鹽類的的作用力，因此我們藉由無機鹽類對於卵磷脂在非極性溶液中的影響與自組裝行為來探討其分子間的作用力，發現與先前文獻有不同的結果。

卵磷脂在非極性有機溶劑中可自組裝形成反球狀微胞，文獻記載添加特定二價及三價陽離子無機鹽類可以使卵磷脂在低極性溶劑中形成反蠕蟲狀微胞，這種長鏈狀的微胞類似高分子鏈會在溶液中糾纏，而使溶液黏度大幅增加，甚至形成黏彈體或凝膠。本研究進一步探討卵磷脂與單價陽離子無機鹽類，包含鋰、鈉、鉀不同鹵化物(氯、溴、碘)的作用力對自組裝結構的影響。我們利用流變儀、小角度X光散射技術分析流變性質與反微胞奈米結構。我們發現鋰離子鹽類可以誘導卵磷脂反球狀微胞結構轉變成反蠕蟲狀微胞且形成黏彈體甚至形成凝膠，鈉離子鹽類中只有碘化鈉可以誘發結構改變，然而鉀離子鹽類則沒有任何明顯變化。因此誘發反球狀微胞轉變成反蠕蟲狀微胞的能力，其效率由高至低為Li+ > Na+ > K+。此外，陽離子與卵磷脂中磷酸根的作用能力間接受到陰離子的影響，其效率由高至低為I− > Br− > Cl−。卵磷脂與無機鹽類之間的作用力是造成不同自組裝行為的主要原因。我們利用傅立葉轉換紅外線光譜儀探討作用力且結果顯示在一價陽離子當中，鋰離子與卵磷脂中帶負電的磷酸根基團作用力最強，而在較大陰離子的存在下，例如碘，陽離子與磷酸根之間的作用力會增強。陽離子與磷酸根的強烈吸引力會使卵磷脂分子緊密排列進而改變分子的幾何形狀，導致形成柱狀微胞而使溶液具有黏彈體或凝膠的性質。

關鍵字

卵磷脂 ； 無機鹽類 ； 反微胞 ； 蠕蟲狀微胞 ； 流變

並列摘要

Biological surfactants play an important role in human bodies, one of the common type of biological surfactants in human body is lecithin, which is main component of cell membranes. Although the content of inorganic salts existing in our body is not much, inorganic salts have a vital impact on our physiological mechanisms. Because the interaction between lecithin and inorganic salts in the aqueous solution is difficult to analyze due to the interference of water molecules, we explore the influence of inorganic salts on the self-assembly behavior of lecithin in a non-polar solvent to clarify the interactions, and we find different results from previous studies.

Lecithin can self-assemble into reverse spherical micelles in non-polar organic solvent. Previous study has shown that the addition of inorganic salts with specific divalent and trivalent cations into lecithin organosols can form reverse wormlike micelles in low polar solvents. The long chain of micelles which are similar to polymer chains entangle in the solution to cause the viscosity to substantially increase, and give rise to a viscoelastic solution or a quasi-permanent gel-like network. This study further investigates the effects of the interactions between lecithin and monovalent cation inorganic salts, including lithium, sodium, potassium with different halides (chloride, bromide, iodide) on the self-assembly structure. We utilized rheology and small-angle X-ray scattering techniques to analyze the rheological properties and the structure of the reverse micelles and we find that all the lithium salts in lecithin organosols can induce the transformation of the original reverse spherical micelles into reverse wormlike micelles to form viscoelastic or even gel-like fluid. In sodium salts, only sodium iodide can induce change of structure, while there is no significant change for all potassium salts. Therefore, the ability to induce the formation of reverse wormlike micelles from high to low is in order of Li+ > Na+ > K+. Furthermore, the ability of the cations to interact with phosphate group of lecithin is indirectly affected by the anions, in order from high to low I− > Br− > Cl−.

The interactions between lecithin and inorganic salts are the key responsible for the different self-assembly behaviors. We used Fourier transform infrared spectroscopy (FTIR) to investigate the interactions and show that among the monovalent cations, lithium ion interacts most strongly with the negatively charged phosphate group (PO2-) of lecithin, and in the presence of large anions, such as iodide, the interaction between cations and phosphate is strengthened. The strong attraction between cation and phosphate forces lecithin molecules to pack more closely and thus changes the effective molecular geometry, which in turn leads to the formation of cylindrical micelles that cause the solutions to be viscoelastic or gel-like.

並列關鍵字

lecithin ； inorganic salt ； reverse micelles ； wormlike micelles ； rheology

參考文獻

Springer: Dordrecht, The Netherlands, 2005; p 233.

1.Scartazzini R, Luisi PL: Organogels from Lecithins. J.

Phys. Chem. 1988, 92, 829-833.

Properties of Polymer-Like Reverse Micelles. Rheol Acta

3.Luisi, P. L.; Scartazzini, R.; Haering, G.;