Twisting and Stretching Single Molecules Adding a twist to DNA
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### Biomembrane Force Probe

Biomembrane Force Probe was pionnered by E. Evans, the principle is simmilar to Micro-pipette or Atomic Force Microscopy (AFM) excepted that the soft spring of the sensor is this time a phospholip vesicle (or the membrane of cell) held by succion in a micro-pipette. The biomembrane force probe (BFP) is a technique pioneered by E.Evans\cite{evan95}. It consists in using the deformation of a 10-20 $\mu$m vesicle under tension as a force sensor. The tension in the vesicle is controlled by a suction pipette that sets the hydrostatic pressure difference across its membrane. The advantage of this technique is that the stiffness of the force sensor (i.e. the tension) can be set at will, allowing for the measurement of a very large range of forces (from $10^{-15}$ to $10^{-9}$ N). This method has been used to monitor the force required to break bonds between pairs of receptor/ligand, antigen/antibody, etc.
 Bibliography 1 Energy landscapes of receptor-ligand bonds explored with dynamic force spectroscopyR. Merkel, P. Nassoy, A. Leung, K. Ritchie, E. Evans, Nature (1999) 397-6714 p.50 PubMed CrosRef