Carl von Ossietzky University of Oldenburg, Center of Interface Science (CIS), Department of Pure and Applied Chemistry, D-26111 Oldenburg, Germany.
Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland.
Colloids Surf B Biointerfaces. 2014 Apr 1;116:389-95. doi: 10.1016/j.colsurfb.2013.12.032. Epub 2013 Dec 25.
Polarization-modulation infrared reflection-absorption spectroscopy, surface pressure measurements and thermodynamic analysis were used to study enzymatic hydrolysis of lipid monolayers at the air/water interface. The Ca(2+)-requiring pork pancreatic phospholipase A2 was used as a catalyst. The substrates were pure 1,2-dilauroyl-sn-glycero-3-phosphocholine or mixed 1,2-dilauroyl-sn-glycero-3-phosphocholine - monosialotetrahexosylganglioside Langmuir films. The physicochemical properties of the monolayers were established with the aim of a correlation with enzyme activity. The infrared spectra were acquired upon the advancement of the catalysis; the latter was studied at a controlled surface pressure and area of the film. Changes of the intensity and frequency of different infrared signals characteristic for the two lipids were correlated with modification of the properties of the monolayer due to hydrolysis. The amide I signal characteristic for peptides permitted detecting the enzyme adsorbed at the interface. The thermodynamic and infrared results indicate that monosialotetrahexosylganglioside increases H-bonding of the lipid polar heads in the films. This effect, which may be responsible for the low activity of phospholipase A2 in the mixed films, could be used for developing enzyme-resistant lipid systems.
采用偏振调制红外反射吸收光谱法、表面压力测量和热力学分析研究了在气/水界面处进行的脂单层的酶促水解。使用 Ca(2+) 依赖性猪胰腺磷脂酶 A2 作为催化剂。底物为纯 1,2-二月桂酰基-sn-甘油-3-磷酸胆碱或混合 1,2-二月桂酰基-sn-甘油-3-磷酸胆碱-单唾液酸四己糖神经节苷脂 Langmuir 膜。通过控制表面压力和膜的面积来建立单层的物理化学性质，以与酶活性相关联。在催化进行时获得红外光谱；在受控的表面压力和膜面积下研究了该反应。由于水解，不同红外信号的强度和频率的变化与单层性质的变化相关联，这些信号特征与两种脂质的性质有关。酰胺 I 信号特征肽允许检测吸附在界面上的酶。热力学和红外结果表明，神经节苷脂增加了膜中脂类极性头部的氢键。这种效应可能是磷脂酶 A2 在混合膜中活性较低的原因，可用于开发抗酶脂系统。
