  Coherent diffraction imaging (CDI) allows the retrieval of the structure of
an isolated object, such as a macromolecule, from its diffraction pattern. CDI
requires the fulfilment of two conditions: the imaging radiation must be
coherent and the object must be isolated. We discuss that it is possible to
directly retrieve the molecular structure from its diffraction pattern which
was acquired neither with coherent radiation nor from an individual molecule,
provided the molecule exhibits periodicity in one direction, as in the case of
fiber diffraction. We demonstrate that by applying iterative phase retrieval
methods to a fiber diffraction pattern, the repeating unit, that is, the
molecule structure, can directly be reconstructed without any prior modeling.
As an example, we recover the structure of the DNA double helix in
three-dimensions from its two-dimensional X-ray fiber diffraction pattern,
Photograph 51, acquired in the famous experiment by Raymond Gosling and
Rosalind Franklin, at a resolution of 3.4 Angstrom.
