Direct Force Measurement of the Interaction Between Liposome and the C2A Domain of Synaptotagmin I using Atomic Force Microscopy

Abstract

The binding force between a liposome and the C2A domain of synaptotagmin I was determined by an atomic force microscopy (AFM). Liposomes were immobilized on the surface of the L1 sensor chip and the C2A domains, which recognize phosphatidylserine, were chemically conjugated onto a gold-coated cantilever tip. The average interaction force between the C2A domain and the liposome was 306 (+/-57) pN while the force between untreated cantilever and the liposome was 58 (+/-16) pN. This work helps understand the physicochemical interactions between proteins and lipid vesicles for the design of high affinity protein probes against the apoptotic cell surface.

Latest developments in experimental and computational approaches to characterize protein–lipid interactions

“…Other techniques such as AFM, and interferometry are less frequently used to detect PLI. AFM has been used to probe PLI (AFM probing) or generate surface images (AFM imaging) of protein–lipid complexes (Fig. E).…”

“…E). The interaction force between phospholipids immobilized on a sensor chip and proteins conjugated on a gold‐coated cantilever was measured using AFM probing to show that lipids can interact with the C2A domain of synaptotagmin I . AFM imaging showed that the α‐synuclein protein penetrated a lipid monolayer and that the dimer form of the protein had higher affinity for the lipid bilayer relative to the monomer .…”

Investigation of penetration force of living cell using an atomic force microscope

“…The atomic force microscope (AFM) is a powerful tool for biological research such as direct force measurement of interaction between liposomes and molecules [7], mechanical properties of living cells [8][9][10][11][12], and penetration forces of living cells [8,13]. As studies on penetration forces of living cells are beginning to emerge, the previous studies focused on the measurement of penetration force based on the shape of the tip [14,15].…”

Interaction of synapsin I with vesicles

“…AFM has shown its advantages for obtaining three-dimensional images of such structures at atomic resolution (Dufrene and Lee 2000;Weerachatyanukul et al 2007). The high sensitivity of the surface scanning probe is what allows direct detection at nanometer-scale through the measure of cantilever deflection as a result of fluctuation of forces between its tip and the sample surface (Park et al 2006;Weerachatyanukul et al 2007). A key aspect of monitoring single-molecule behavior using this technique is the immobilization of the molecules to a solid supported surface in a controlled fashion.…”

“…It is of further interest to us to determine the importance of the syn Ia C-domain in vesicle recognition. AFM lends itself well to such a study as this technique has been used to measure binding forces of biomolecular interactions (Yoshimura et al 2006;Park et al 2006;Liu et al 2007). In our study we have developed an efficient method to tether SVs to the scanning surface in a controlled fashion, one now only has to concentrate on coupling either full-length synapsin or synapsin peptides to the silicon nitride cantilever in order to obtain single molecule force measurements of the binding force between syn Ia-LUVs.…”