Studying intermolecular processes in thin surface layers with microcantilever transducers. Formation of protein fibrils on a solid support

Abstract

The possibility of studying the processes of intermolecular interaction in thin surface layers by means of microcantilever transducer (MCT) are considered. The use of MCT makes it possible to observe the catalytic growth of amyloid fibrils from chemically immobilized lisozyme molecules on the gold or silicon supports at enhanced acidity (pH 3.0) and room temperature, whereas aggregation in the volume occurs under the same conditions at a higher temperature of 57°C. Forces that arise in the monolayer protein films during their aggregation are analyzed. A correlation is revealed between the development of lateral strains and the growth rate of protein fibrils in the monolayer. It is shown that for a protein covalently immobilized on the silicon (mica) surface, the aggregation rate is 4.6 (as revealed by the analysis of kinetic data on the caltilever bending) and 5 times (according to estimates of the number of fibrils in an AFM image) slower than on the gold surface. A model for calculating the pair interactions between protein molecules in a monolayer during their aggregation is proposed. Using this model and based on the experimental data, the pair interaction forces of lysozyme molecules on the gold and silicon surfaces are calculated. The calculated forces coincide in the order of magnitude with the data of force spectroscopy on the artificial expansion of an aggregate of lysozyme molecules T4 [23]. It is confirmed experimentally that chemical immobilization of lysozyme on the mica surface leads to deformation (flattening) of protein molecules as compared with their native conformation.