胶束模拟酶研究

STUDIES ON MICELLAR IMITATION ENZYMES

用表面张力法测定了表面活性剂Brij35、Brij58、Tritonx-100、SDS和25℃,35℃,45℃时的临界胶束浓度(CMC),并用小角激光光散射法加以确证。以这些胶束为酶模型,研究了它们对芳环亲核取代反应的催化作用。结果表明,非离子型胶束对2,4—二溴化雌甾醇的羟基化有明显催化效果。

The critical micellar concentration CMC's of surfactants Brij 35, Brij 58, Tritonx-100. SDS and DTA are determined at 25℃. 35℃. 45℃. by surface tensioon. and the results are tested by low-angle laser light scattering The nucleophilic substitution reaction on o-Bromotoluene and p-Bromotoluene in the NaOH aqueous-Cu_2O-NH_4Cl-nonionic micelles systems at 45℃ has been studied, it is found that the o-hydroxytoluene and p-methylphenol are formed after 12 hours. This indicates the nonionic micelle possesses the catalytic effect for the nucleophilic substibution of the hydroxhl group for the Bromo atom on aromatic ring, since without micelles, no o-hydroxytotuene and p-methyiphenol can be detected. The catalytic that possesses Loose and porous feature with transport functioon. However. the Euclidean structure of micelles is too tight to make the reactants and products to freely move in micellar systems. Finally, the nucleophilic substitution on Ring A of 2, 4-dibromoestradiol in micelle Brij 35-NaOH-Cu_2O-NH_4Cl-water systems at 45℃ has been studied and it is found that 2, or 4 hydroxyestradiol and 2,4-dihydroxyestradiol are formed after 14 hours as indicated by TLC. The conversion of 2. 4-dibromoestradiols into the corrsponding dihydroxyestradiols is in essence a non-activated nucleophilic aromatic substitution. Under ordinary conitions, such type of substitution usually proceeds with extreme difficnlty, stringent conditions being required. Here. we apply the method developed by us to the direct conversion of 2-and /or -4-bormoestradiols into the corresponding hydroxyestradiols. As was pointed out therein, this reaction can be aided by the concordant action of the coordination of the sodium ion with micelle Brij 35 and of Cu_2O toward aryl halide with the results that the nucleophilicity of the hy droxy ion is enhanced and the carbon-halogen bond weakened. Therefore. the substitution can be effected under mild reaction conditions. Although promising inauguration is really remarkable, further and detailed works are still remained to be desired to shed light on this kind of enzyme models.