Hoda Kazuki, Kawasaki Hideya, Yoshino Norio, Chang Chien-Hsiang, Morikawa Yoko, Sugihara Gohsuke, Shibata Osamu
Division of Biointerfacial Science, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Colloids Surf B Biointerfaces. 2006 Nov 1;53(1):37-50. doi: 10.1016/j.colsurfb.2006.07.019. Epub 2006 Aug 7.
Two-component Langmuir monolayers formed on 0.02 M Tris buffer solution (pH 7.4) with 0.13 M NaCl at 298.2K were investigated for two different fluorinated-hydrogenated hybrid amphiphiles (F6PH5PPhNa and F8PH5PPhNa or F6 and F8, respectively) with DPPC. Surface pressure (pi), surface potential (DeltaV) and dipole moment (mu( perpendicular)) as a function of molecular surface area (A) were measured by employing the Whilhelmy method and an ionizing electrode method. From the A- and DeltaV-X(F6) (or X(F8)) curves, partial molecular surface area (PMA) and apparent partial molecular surface potential (APSP) were determined as a function of surface mole fraction (X(Fn)) at discrete surface pressures. Then, the behavior of occupied surface areas and surface potentials of the respective components could be made clearer. Compressibility (C(s)), elasticity (C(s)(-1)), and excess Gibbs energy (DeltaG((ex))) as a function of X(F6) (or X(F8)) were estimated at definite pressures. These physico-chemical parameters were found to reflect the mechanical strength of monolayer films formed. The regular solution theory being applied to DeltaG((ex)), the activity coefficients (f) as well as the interaction parameter (I(p)) between DPPC and two hybrid amphiphiles in the binary monolayers were evaluated. I(p) values thus obtained indicated that F8 molecules interact more strongly with DPPC molecules than F6. Moreover, in order to better understand the morphological monolayer state, Langmuir-Blodgett (LB) films made from DPPC and fluorinated-hydrogenated hybrid amphiphiles were examined by atomic force microscopy (AFM). The miscibility of the two components in the monolayer state is evidenced by these thermodynamic quantities and AFM observations. Furthermore, AFM images demonstrated that F8 could more effectively disperse the ordered domains of DPPC than F6.
研究了在298.2K下，于含有0.13M NaCl的0.02M Tris缓冲溶液（pH 7.4）上形成的双组分朗缪尔单分子层，该单分子层由两种不同的氟化 - 氢化混合两亲物（分别为F6PH5PPhNa和F8PH5PPhNa或F6和F8）与二棕榈酰磷脂酰胆碱（DPPC）组成。采用威尔海姆法和电离电极法测量了表面压力（π）、表面电势（ΔV）和偶极矩（μ(⊥)）随分子表面积（A）的变化。根据A - 和ΔV - X(F6)（或X(F8)）曲线，在离散的表面压力下，确定了部分分子表面积（PMA）和表观部分分子表面电势（APSP）随表面摩尔分数（X(Fn)）的变化关系。然后，各组分占据的表面积和表面电势的行为就可以更清晰地呈现出来。在确定的压力下，估算了压缩性（Cs）、弹性（Cs(-1)）和过量吉布斯自由能（ΔG((ex))）随X(F6)（或X(F8)）的变化关系。发现这些物理化学参数反映了形成的单分子层膜的机械强度。将正规溶液理论应用于ΔG((ex))，评估了二元单分子层中DPPC与两种混合两亲物之间的活度系数（f）以及相互作用参数（Ip）。由此获得的Ip值表明，F8分子与DPPC分子的相互作用比F6更强。此外，为了更好地理解单分子层的形态状态，通过原子力显微镜（AFM）检查了由DPPC和氟化 - 氢化混合两亲物制成的朗缪尔 - 布洛杰特（LB）膜。这些热力学量和AFM观察结果证明了两种组分在单分子层状态下的混溶性。此外，AFM图像表明，与F6相比，F8能够更有效地分散DPPC的有序区域。
