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本文报道了具有类似环葡萄糖疏水内穴特性但长度及内穴尺寸为可变化的羧甲基糖淀粉钠(Na-CMA)螺旋构象对具有长链烷基的受物:十六烷基三甲基氯化铵(CTACl)、十二烷基三甲基碘化铵(LTAI)和十二烷基硫酸钠(NaLS)的包结作用。使用表面张力法求得Na-CMA—CTACl包结常数在1.27～2.30×10~4M~(-1)左右,Na-CMA—LTAI为0.52×10~3M~(-1),Na-CMA—NaLS为0.73×10~3M~(-1),表明与阴或阳离子的受物均可形成稳定包结络合物,稳定程度由受物烃链疏水性决定。Na-CMA的最大结合部位对于CTACl,LTAI,NaLS分别为7.7,9.8,10与形成6-螺旋和受物分子相对长度推算出的数值很接近。从Na-CMA—CTACl包结常数与温度的关系求得包结过程的热力学参数为ΔG_(298)=-5.7kcal/mol,ΔH_(298)=3.5kcal/mol,ΔS_(298)=7.6 e.u.。说明包结驱动力不同于典型疏水作用的熵控制和环葡萄糖包结的焓控制机制。根据粘度和表面张力的测定提出了这种包结过程伴随着Na-CMA链从紧密线团至间断螺旋的构象变化,反映出Na-CMA与环葡萄糖不同的特性,看来更适合于作为生物大分子识别受物的模型。
In this paper, we report the effects of sodium carboxymethyl starch glycolate (Na-CMA) helical conformation with a similar ring-like hydrophobicity but with varying length and pocket size on the long-chain alkyl groups: cetyltrimethylammonium (CTACl), lauryltrimethylammonium iodide (LTAI) and sodium lauryl sulfate (NaLS). The packing constants of Na-CMA-CTACl obtained by surface tension method are about 1.27 ~ 2.30 × 10 ~ 4M ~ (-1), Na-CMA-LTAI is 0.52 × 10 ~ 3M ~ (-1) The NaLS is 0.73 × 10 ~ 3M ~ (-1), indicating that the stable inclusion complex can form with the acceptor of anion or cation. The degree of stability is determined by the hydrophobicity of the hydrocarbon chain. The maximum binding sites for Na-CMA for CTACl, LTAI, and NaLS are 7.7, 9.8, and 10, respectively, which are close to those derived from the relative lengths of formed 6-helix and acceptor molecules. The thermodynamic parameters of the inclusion process were calculated from the relationship between the enthalpy of formation and the temperature of Na-CMA-CTACl. ΔH 298 = -5.7 kcal / mol, ΔH 298 = 3.5 kcal / mol and ΔS 298 = 7.6 eu . It shows that enthalpy control mechanism of entrainment driving force is different from entropy control of typical hydrophobic interaction and inclusion of cyclic glucose. According to the determination of viscosity and surface tension, the conformational change of Na-CMA chain from the tight coil to the interrupted spiral is proposed in this inclusion process, which reflects the different characteristics of Na-CMA and cyclodextrin. It seems more suitable as a biological Macromolecules recognize the receptor model.