ABSTRACT
There are many different ways of characterizing biological structures. A useful alternative to the deterministic description of structure in terms of well-defined atomic coordinates is the use of statistical descriptions. For example, the arrangement of a large DNA molecule within the cell is often best characterized statistically in terms of average quantities such as the mean size and position. The study of structure is often a prerequisite to tackling the more interesting question of the functional dynamics of a particular macro-molecule or macromolecular assembly. The notion of structure is complex and ambiguous. In the context of crystals, people can think of structure at the level of the monotonous regular packing of the atoms into the unit cells of which the crystal is built. In the context of polymeric systems such as DNA, the notion of structure brings us immediately to the question of the relative importance of universality and specificity in macromolecules.
