Caseli Luciano, Masui Douglas C, Furriel Rosa P M, Leone Francisco A, Zaniquelli Maria E D, Orbulescu Jhony, Leblanc Roger M
Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil 14040-901.
J Colloid Interface Sci. 2008 Apr 15;320(2):476-82. doi: 10.1016/j.jcis.2008.01.043. Epub 2008 Feb 2.
A glycosylphosphatidylinositol (GPI)-anchored enzyme (rat osseous plate alkaline phosphatase-OAP) was studied as monolayer (pure and mixed with lipids) at the air-water interface. Surface pressure and surface potential-area isotherms showed that the enzyme forms a stable monolayer and exhibits a liquid-expanded state even at surface pressure as high as 30 mN m(-1). Isotherms for mixed dimyristoylphosphatidic acid (DMPA)-OAP monolayer showed the absence of a liquid-expanded/liquid-condensed phase transition as observed for pure DMPA monolayer. In both cases, pure or mixed monolayer, the enzyme preserves its native conformation under compression at the air-water interface as observed from in situ p-polarized light Fourier transform-infrared reflection-absorption spectroscopic (FT-IRRAS) measurements. Changes in orientation and conformation of the enzyme due to the presence or absence of DMPA, as well as due to the surface compression, are discussed.
一种糖基磷脂酰肌醇（GPI）锚定酶（大鼠骨板碱性磷酸酶 - OAP）在空气 - 水界面以单层形式（纯酶以及与脂质混合）进行了研究。表面压力和表面电位 - 面积等温线表明，该酶形成了稳定的单层，甚至在高达30 mN m⁻¹的表面压力下仍呈现液 - 胀状态。混合二肉豆蔻酰磷脂酸（DMPA） - OAP单层的等温线显示，未观察到纯DMPA单层中出现的液 - 胀/液 - 凝相变。在纯单层或混合单层这两种情况下，通过原位p偏振光傅里叶变换红外反射吸收光谱（FT - IRRAS）测量观察到，该酶在空气 - 水界面压缩下保持其天然构象。讨论了由于DMPA的存在与否以及表面压缩导致的酶的取向和构象变化。
