Jun 28th AM

Today, we looking at the binding force between an antibody and an antigen. To do this, the cantilever tip is covalently bound to an antibody using amino groups. The antigen is fixed and covalently bound to the glass-slide. The tip with the antibody is lowered onto the surface of the slide and the binding force between the antibody and the antigen can be measured. The cantilever was put in oscilating mode. As the cantilever tip is being pulled from the surface, the antibody molecule unfolds and the interaction forces between the antibody and antigen is recorded on a graph. A computer program would calculate the interaction forces which is in pN. Very specific binding would take a larger force to pull antigen apart from antibody. Non-specific binding would require less force to separate antigen from antibody. Sometimes we see much more forces and a jagged recording on the graph. This may be due to multiple antigens binding to the antibody. Proteins denature after 2 hrs. and a new sample needs to be used after 2 hours.