PHASE SEPARATION AND REACTIVITY CHANGES OF PHENYL ESTER SUBSTRATE AND IMIDAZOLE CATALYST IN THE DIALKYLAMMONIUM BILAYER MEMBRANE
PHASE SEPARATION AND REACTIVITY CHANGES OF PHENYL ESTER SUBSTRATE AND IMIDAZOLE CATALYST IN THE DIALKYLAMMONIUM BILAYER MEMBRANE
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苯酯底物和咪唑催化剂在二烷基铵双层膜中的相分离和反应性变化
DOI：
10.1002/chin.198351068
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Y. Okahata
中科院分区：
文献类型：
--
作者：
T. Kunitake;H. Ihara;Y. Okahata
合成了具有偶氮苯发色团并能形成双层结构的苯酯底物和咪唑催化剂。这些两亲分子在二烷基铵双层基质中的分布通过使用由于偶氮苯发色团簇形成的蓝移来检查。基质中浓度的增加和基质的液晶-晶体相变促进了基质簇的形成。除了这些因素外，由于介质pH值的变化或由于与Cu ~（2+）离子的络合，阴离子组氨酸头基的中和也促进了催化剂簇的形成。在10 ℃、pH11.8下，成簇底物的碱性水解速率小于分离的（单体）底物：*/19. Arrhenius图显示了由于单体-团簇比的变化而导致的基体相变附近的拐点区域。对硝基苯基/N-苄氧羰基-L-苯丙氨酸酯水解的活化能在部分刚性双层基质中为27 kcal/mol，但在流体基质中降低至14 kcal/mol。这一变化归因于刚性基体中催化剂簇的形成。本研究首次提供了相分离控制反应的实例，生物膜的生理功能与膜酶的分布方式及相应的活性变化密切相关。1-6尽管这些酶的活性调节在生理学上具有重要意义，但由于系统的复杂性而产生的固有困难，对其分子的理解是滞后的。因此，调节的分子机制可以通过使用简化的合成系统更容易地测试。
A phenylester substrate and an imidazole catalyst that possess the azobenzene chromophore and are capable of bilayer formation were synthesized. Distribution of these amphiphiles in the dialkylammonium bilayer matrix was examined by using blue shifts due to cluster formationof the azobenzene chromophore. Formation of the substrate cluster was promoted by increased concentrations in the matrix and by the liquid crystal-to-crystal phase transition of the matrix. Formation of the catalyst cluster was promoted, in addition to these factors, by neutralizationof the anionic histidine head group due to the change of the medium pH or due to complexation with Cu2+ ion. The rate of alkaline hydrolysis of the clustered substrate was smaller than that of the isolated (monomeric) substrate:*/i9 at 10 C, pH 11.8. The Arrhenius plots show inflection regions near the phase transitionof the matrix due to changing monomer-cluster ratios. The activation energy of the hydrolysis of p-nitrophenyl/V-carbobenzoxy-L-phenylalaninate was 27 kcal/mol in the partially rigid bilayer matrix but decreased to 14 kcal/mol in the fluid matrix. This change was attributed to the formation of the catalyst cluster in the rigid matrix. The present study provides the first example of the reaction control by phase separation.The physiological function of the biomembrane is closely related to the mode of distribution and the corresponding activity change of membrane enzymes. 1-6 In spite of the overriding physiological importance of the regulation of activity of these enzymes, its molecular understanding is lagging because of the inherent dif-ficulty arising from the complexity of the system. Thus, the molecular mechanism of regulation may be tested more readily by using simplified, synthetic systems.