Rosalind Franklin and X-ray Diffraction

Rosalind Franklin Born in July 25, 1920 in London, England Died April 16,1958 in London, England (ovarian cancer)

Attended and excelled at an all girl’s school in London (the school taught chemistry and physics) Graduated in 1941from Newman College, Cambridge 1942 worked at British Coal Utilization Association (studying carbon and graphite microstructures) 1945 earned Ph.D. in physical chemistry from Cambridge University worked in Paris where she learned X- ray diffraction techniques Accomplishments

1951-returned to London to work in John Randall’s laboratory at King’s College, London as a research assistant came close to solving the DNA structure Moved to J. D. Bernal’s Lab at Birkbeck College and worked on tobacco mosaic virus and the polio virus

X-ray diffraction Definition –The scattering of x-rays by crystal atoms that produces a pattern that yields information about the structure of the crystal. The wavelengths of x-rays are comparable in size to the distances between atoms in most crystals. X-ray diffraction is the basis of x-ray crystallography

X-ray diffraction is used to be able to determine the structural information about crystalline structures –Can be used on complex biomolecules to determine their 3-D shapes Used in: –Solid-state physics –Biophysics –Medical physics –Chemistry –biochemistry

A Brief History of X-ray diffraction 1895—first discovered by Roentgen 1914—first diffraction pattern made of a crystal 1915—theory proposed to determine crystal structures from diffraction patterns 1953—Watson and Crick propose the DNA structure with the aid of photo 51 from Rosalind Franklin Current—through use of computer aided technology, atomic structures are being determined as well as uses in medical applications

How diffraction works Diffraction can be used on various materials including a single particle, solids, and crystalline materials. –Single particles Incident beams scatter uniformly –Solids beams scatter and interfere constructively in some patterns. This will produce diffracted beams Random arrangements of material will cause beams to randomly interfere and will not produce a distinctive pattern

How diffraction works (cont’d) –Crystalline materials Regular patterns of crystalline materials produce distinct diffraction patterns The type of patterns produced gives information about the crystal structure of the material tion/what_is_diffraction.htm

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X-ray diffraction diagram X-raystm.pdf

Analyzing patterns Data is complied from all angles There are recognizable patterns for simple crystal structures Diffraction patterns taken from each angle can be complied to produce a 3-D electron density map

The scientists behind the discovery of the DNA structure Several scientists were involved –Rosalind Franklin: physical chemist and expert in x-ray crystallography Was the first person to crystallize and photographed B-DNA Famous Photo html#fea_top

Maurice Wilkins –Peer and collaborator of Rosalind Franklin James Watson and Francis Crick –Chemists –Used information from Rosalind Franklin’s Photo 51 and molecular modeling to solve the structure of DNA in 1953

Analysis of Photo 51 Showed the now famous “X” pattern of the helical shape The diamond shapes in the photo indicate long, extended molecules The spacing in the photograph is smeared which indicates distances between repeating structures In the photograph there appears to be missing smears. This indicates an interference from the second helix structure

Analysis of Photo 51 Showed the now famous “X” pattern of the helical shape The diamond shapes in the photo indicate long, extended molecules The spacing in the photograph is smeared which indicates distances between repeating structures In the photograph there appears to be missing smears. This indicates an interference from the second helix structure

Analysis of Photo 51 Showed the now famous “X” pattern of the helical shape The diamond shapes in the photo indicate long, extended molecules The spacing in the photograph is smeared which indicates distances between repeating structures In the photograph there appears to be missing smears. This indicates an interference from the second helix structure

Analysis of Photo 51 Showed the now famous “X” pattern of the helical shape The diamond shapes in the photo indicate long, extended molecules The spacing in the photograph is smeared which indicates distances between repeating structures In the photograph there appears to be missing smears. This indicates an interference from the second helix structure

Analysis of Photo 51 Showed the now famous “X” pattern of the helical shape The diamond shapes in the photo indicate long, extended molecules The spacing in the photograph is smeared which indicates distances between repeating structures In the photograph there appears to be missing smears. This indicates an interference from the second helix structure

The secrets of Photo 51 After analysis of Photo 51, the following information was obtained: –The structure was a double helix –The radius of the structure is 10 angstroms –The distance between nitrogen bases is 3.4 angstroms –The distance between each turn of the helix is 34 angstroms

Secrets of Photo 51 The use of Photo 51 along with other discoveries lead to the following: –DNA was made up of a sugar, a phosphate group and 4 nitrogenous bases (adenine, thymine, cytosine, and guanine ) –Chargaff’s Rule applies here: The same amounts of adenine and thymine are found in DNA The same amounts of cytosine and guanine are found in DNA %A=%T %C=%G

Modeling DNA James Watson and Francis Crick modeling DNA structure emach/pharmaceuticals/watson-crick.html

References (n.d.). X-Ray Diffraction Message posted to (n.d.). Rosalind Elsie Franklin Message posted to ( n.d.). What is X-Ray Diffraction Message posted to (n.d.). X-Ray DIffraction Message posted to ( n.d.). X-Ray Diffraction-FInding the Structure of DNA Message posted to Ardell, D. (2006, Oct. 25). Rosalind Franklin ( ) Message posted to Day, E. & Ross, S. (2004). X-Ray Diffraction Message posted to Diffraction