2. What is x-ray crystallography and why is it important?

The shape of crystals in one form or another has been known since early times. Observation over a number of centuries had also confirmed the constancy of their shape. An understanding of their underlying structure, however, had to wait until the late eighteenth century when John Dalton put forward the idea that atoms of different elements might combine together in various proportions to make compound atoms or molecules as we call them today. The various optical properties of crystals were also of interest and many observations were made with visible light about the ways in which rays of light of various colours could be absorbed, reflected and refracted in their passage through crystals.

The discovery by Wilhelm Konrad von Roentgen in 1895 of x-rays, which unlike light could pass through opaque objects, allowed the studies to be taken further and by 1912 Max von Leue and PP Ewald had deduced that x-rays must be capable of being diffracted, like light. Shortly after the crystallographers Friedrich and Knipping passed a beam of x-rays through a crystal of copper sulphate on to a photographic plate. When the plate was developed, in addition to the dark spot produced by the undeflected beam, they also found an irregular pattern of black spots confirming the theory and encouraging the idea that the pattern of diffraction (the scattering of the spots) said something measurable about the molecular structure of the crystal. Concerted work by a number of scientists including Sir William Bragg and JD Bernal led both to the deduction of the molecular structure of a number of crystals and deduction of equations to interpret their use. In March 1929 the Royal Institution established three committees on x-ray crystallography.

When the technique of x-ray diffraction was used on protein molecules in the 1930s, the growing possibility of the technique was recognised.






								next >


		2. What is x-ray crystallography and why is it important? The shape of crystals in one form or another has been known since early times. Observation over a number of centuries had also confirmed the constancy of their shape. An understanding of their underlying structure, however, had to wait until the late eighteenth century when John Dalton put forward the idea that atoms of different elements might combine together in various proportions to make compound atoms or molecules as we call them today. The various optical properties of crystals were also of interest and many observations were made with visible light about the ways in which rays of light of various colours could be absorbed, reflected and refracted in their passage through crystals. The discovery by Wilhelm Konrad von Roentgen in 1895 of x-rays, which unlike light could pass through opaque objects, allowed the studies to be taken further and by 1912 Max von Leue and PP Ewald had deduced that x-rays must be capable of being diffracted, like light. Shortly after the crystallographers Friedrich and Knipping passed a beam of x-rays through a crystal of copper sulphate on to a photographic plate. When the plate was developed, in addition to the dark spot produced by the undeflected beam, they also found an irregular pattern of black spots confirming the theory and encouraging the idea that the pattern of diffraction (the scattering of the spots) said something measurable about the molecular structure of the crystal. Concerted work by a number of scientists including Sir William Bragg and JD Bernal led both to the deduction of the molecular structure of a number of crystals and deduction of equations to interpret their use. In March 1929 the Royal Institution established three committees on x-ray crystallography. When the technique of x-ray diffraction was used on protein molecules in the 1930s, the growing possibility of the technique was recognised.