The Stiffness of a Biomembrane Force Probe Vesicle

Abstract

The biomembrane force probe is an experimental apparatus that has been developed to measure the response of a single molecular bond to applied force. A key element in the probe is a small vesicle that is held and manipulated by means of a pipette tip. The interest in this element is due to the fact that it is positioned in series with the bond being interrogated. As a result, the interpretation of data hinges on a knowledge of the mechanical properties, principally the load versus deflection behavior, of the vesicle. Under the assumptions that the vesicle has fixed membrane surface area and fixed internal volume, its load—deflection behavior is considered here. The analysis is exact but the final result does not appear in closed form1 consequently, it must be evaluated by numerical means. For a given geometry, the initial stiffness is found to scale with the pipette pressure and pipette channel radius.