Evaluation of intermolecular forces between lipopolysaccharides and monoclonal antibodies using atomic force microscopy.

Understanding of interactions between a bacterium and an immune or non-immune host organism at the cellular and subcellular level is important in order to improve new and existing immunobiological tools for the treatment of bacterial infections (including pseudotuberculosis). The aim of this work was to quantify the interaction force between Yersinia pseudotuberculosis and monoclonal antibodies (mAbs) in the model system "lipopolysaccharide (LPS) - mAbs" by atomic force microscopy (AFM). Our research findings provided the methodical approaches to force measurements between an AFM probe, which was functionalized with Y. pseudotuberculosis LPS, and mica coated by different mAbs. Based on the criteria for force estimation there was shown a greater binding force in the system "LPS - complementary mAbs" than in the system "LPS - heterologous mAbs". In both cases binding force increase followed by increase a contact time between the functionalized AFM probe and mica from 1 to 5 s. It has been shown that single bonds between LPS and complementary mAbs molecules also included a clearly defined non-specific component along with immunochemically specific one. The evidence suggests a significant proportion of applied force exerted to unfolding of high-molecular aggregates whose length may attain many hundreds of nanometers.