![]() Franklin later defined the drier DNA conformation as the A-Form DNA and the wetter DNA conformation as B-Form DNA. Throughout Franklin´s early work at King´s College London, she found that DNA fibers with a higher water content produced a different diffraction pattern than DNA fibers with a lower water content, indicating that wet and dry DNA adopted different three-dimensional conformations. Before joining the lab, Franklin conducted X-ray diffraction experiments on carbon compounds at a government lab in Paris, France, and published several papers on X-ray crystallography of coal and coal compounds. The resulting X-ray diffraction pattern of DNA was of a higher quality than any patterns collected prior.įranklin, a specialist in X-ray crystallography, continued previous X-ray crystallography experiments on DNA with Gosling when she joined the King´s College London lab in 1951. Furthermore, the two researchers kept the DNA fibers wet with water by keeping them in a humid environment. When mounting the DNA fibers for viewing, Wilkins and Gosling were able to bundle many of the thin fibers together and pull them tight to provide a larger sample to better diffract X-rays. Wilkins and his graduate student, Raymond Gosling, later Franklin´s graduate student, collected X-ray diffraction patterns of DNA purified in a way that produced longer fibers than those accessible to Astbury. Maurice Wilkins, a scientist working at King´s College London, collected X-ray diffraction patterns of DNA in 1950. In 1944 Oswald Avery, Colin MacLeod and Maclyn McCarty published an experiment that isolated DNA as the material that contained genes. However, at that time scientists generally agreed that DNA merely provided structural support for cells and that protein must be genetic material. At the time of Astbury´s experiments, scientists had determined the chemical composition of DNA. However, Astbury´’s diffraction patterns were blurry and difficult to interpret. William Thomas Astbury, a crystallographer working at the University of Leeds in Leeds, England, gathered the first diffraction patterns of DNA in 1937. Scientists began collecting X-ray diffraction patterns of DNA in the 1930s before they confirmed that DNA contained genes. The pattern of dark marks on the film gives scientists information about the structure of the crystal. When the X-rays scatter, they strike a film mounted behind the crystal and leave a pattern of dark marks. When X-rays interact with electrons in a crystal the X-rays scatter, or diffract, at angles that indicate the arrangement of atoms in the crystal, or its structure. Because of their short wavelength, X-rays can pass through a crystal and interact with the electrons of the atoms within the crystal. X-rays are electromagnetic waves that have a shorter wavelength and higher energy than visible light. The X-ray tube generates X-rays that strike the purified material. To perform an X-ray crystallography, scientists mount a purified fiber or crystal in an X-ray tube. Photo 51 used DNA fibers, DNA crystals first produced in the 1970s. Some biological macromolecules, such as DNA, can form fibers suitable for analysis using X-ray crystallography because their solid forms consist of atoms arranged in a regular pattern. Crystals are solids with regular, repeating units of atoms. X-ray crystallography, the technique Franklin used to produce Photo 51 of DNA, is a method scientists use to determine the three-dimensional structure of a crystal. Franklin´s Photo 51 helped scientists learn more about the three-dimensional structure of DNA and enabled scientists to understand DNA´s role in heredity. In 1962, after Franklin´s death, Watson, Crick, and Wilkins shared the Nobel Prize in Physiology or Medicine for their findings about DNA. Watson and Crick used that image to develop their structural model of DNA. Maurice Wilkins, Franklin´s colleague showed James Watson and Francis Crick Photo 51 without Franklin´s knowledge. Franklin took Photo 51 after scientists confirmed that DNA contained genes. Photograph 51, or Photo 51, revealed information about DNA´s three-dimensional structure by displaying the way a beam of X-rays scattered off a pure fiber of DNA. On, at King´s College London in London, England, Rosalind Franklin photographed her fifty-first X-ray diffraction pattern of deoxyribosenucleic acid, or DNA. Photograph 51, by Rosalind Franklin (1952) ![]()
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