Rosalind Elsie Franklin was a British chemist and X-ray crystallographer whose work was central to the understanding of the molecular structures of DNA, RNA, viruses, coal, and graphite. Although her works on coal and viruses were appreciated in her lifetime, Franklin's contributions to the discovery of the structure of DNA were largely unrecognized during her life, for which Franklin has been variously referred to as the "wronged heroine", the "dark lady of DNA", the "forgotten heroine", a "feminist icon", and the "Sylvia Plath of molecular biology".
Rosalind Franklin
Franklin at work, 1955
A satirical death note of A-DNA helix by Franklin and Gosling.
An electron micrograph of tobacco mosaic virus
X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract in specific directions. By measuring the angles and intensities of the X-ray diffraction, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal and the positions of the atoms, as well as their chemical bonds, crystallographic disorder, and other information.
A powder X-ray diffractometer in motion
Drawing of square (A) and hexagonal (B) packing from Kepler's work, Strena seu de Nive Sexangula.
One of the copper sulfate X-ray interference patterns published in Von Laue's 1912 paper.
Although diamonds (top left) and graphite (top right) are identical in chemical composition—being both pure carbon—X-ray crystallography revealed the arrangement of their atoms (bottom). In diamond, the carbon atoms are arranged tetrahedrally and held together by single covalent bonds. By contrast, graphite is composed of stacked sheets. Within the sheet, the bonding is covalent and has hexagonal symmetry, but there are no covalent bonds between the sheets.