Smith L J, Clark D C
AFRC Institute of Food Research, Colney, Norwich UK.
Biochim Biophys Acta. 1992 May 22;1121(1-2):111-8. doi: 10.1016/0167-4838(92)90344-d.
A new circular dichroism (CD) technique is presented which quantifies, in situ, the changes in protein and peptide secondary structure upon adsorption at the quartz/liquid interface. Far-UV CD spectra of adsorbed proteins were recorded from several quartz interfaces contained in a specially constructed cell. Adsorbed, oriented alpha-helical spectra were recorded from hydrophilic and hydrophobic quartz using the bee venom peptide, melittin, which can be induced into an alpha-helical, tetrameric conformation in solution. The hydrophobic quartz provides a model system for oil-in-water emulsions and cell membranes. Surface concentrations were determined by radio-counting and were dependent on the nature of the surface. The characterization of these spectra has been partly achieved using far-UV CD spectra obtained from melittin adsorbed onto hydrophilic colloidal silica particles, where orientation effects are eliminated. Analysis of these spectra reveals considerable denaturation of the helical structures upon adsorption. Surface concentrations from the silica were determined from adsorption isotherms. The surface orientation of adsorbed melittin was dependent on the state of aggregation and hence degree of helicity of the molecule. These results support a model for the mode of action of melittin in lysing membranes.
本文介绍了一种新的圆二色性（CD）技术，该技术可原位定量蛋白质和肽在石英/液体界面吸附时二级结构的变化。从特制池中包含的多个石英界面记录吸附蛋白质的远紫外CD光谱。使用蜂毒肽蜂毒素，从亲水性和疏水性石英记录吸附的、取向的α-螺旋光谱，蜂毒素在溶液中可诱导形成α-螺旋四聚体构象。疏水性石英为水包油乳液和细胞膜提供了一个模型系统。通过放射性计数确定表面浓度，其取决于表面的性质。利用从吸附在亲水性胶体二氧化硅颗粒上的蜂毒素获得的远紫外CD光谱，部分实现了对这些光谱的表征，其中消除了取向效应。对这些光谱的分析表明，吸附后螺旋结构发生了相当程度的变性。根据吸附等温线确定二氧化硅的表面浓度。吸附的蜂毒素的表面取向取决于聚集状态，因此取决于分子的螺旋度。这些结果支持了蜂毒素裂解膜作用模式的模型。
