Introduction to single molecule experiments in biophysics

Felix Ritort

From DNA to proteins, biomolecules carry out very specialized tasks
inside the cell. During the past years, because of fast advances
experienced by nanotechnologies, it has become possible to use single
molecule experiments in order to manipulate, influence and follow the
tasks performed by individual biomolecules. This new technologies
offer high potentialities in physics and biology. A clue to understand
the relevance of these new phenomena in non-equilibrium physics lies
on the smallness of the energies involved which are only few times KT
(K being the Boltzmann constant and T the room temperature). In this
regime, thermal fluctuations and large deviations from the average
behavior are important, paving the way to understand the thermodynamic
behavior of small systems in non-equilibrium conditions. At the same
time, these technologies provide us with novel information about
biomolecular processes occurring inside the cell, hardly accessible
with traditional biochemistry methods.

In these lectures I will review the different experimental techniques
used to manipulate single molecules such as atomic force microscopy,
optical and magnetic tweezers or fluorescence techniques. We will
cover the basic principles, the different domains of applicability as
well as their implementation to investigate specific problems in
molecular biophysics.