  Biophysicists and structural biologists increasingly acknowledge the role
played by the mechanical properties of macromolecules as a critical element in
many biological processes. This change has been brought about, in part, by the
advent of single molecule biophysics techniques that have made it possible to
exert piconewton forces on key macromolecules and observe their deformations at
nanometer length scales, as well as to observe the mechanical action of
macromolecules such as molecular motors. This has opened up immense
possibilities for a new generation of mechanical investigations that will
respond to such measurements in an attempt to develop a coherent theory for the
mechanical behavior of macromolecules under conditions where thermal and
chemical effects are on an equal footing with deterministic forces. This paper
presents an application of the principles of mechanics to the problem of DNA
packaging, one of the key events in the life cycle of bacterial viruses with
special reference to the nature of the internal forces that are built up during
the DNA packaging process.
