rosalind franklin and x-ray diffraction. rosalind franklin born in july 25, 1920 in london, england...
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![Page 1: 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)](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649e615503460f94b5c584/html5/thumbnails/1.jpg)
Rosalind Franklin and X-ray Diffraction
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Rosalind Franklin• Born in July 25, 1920 in
London, England• Died April 16,1958 in
London, England (ovarian cancer)
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• 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
• 1947-1950 worked in Paris where she learned X-ray diffraction techniques
Accomplishments
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Accomplishments
• 1951-returned to London to work in John Randall’s laboratory at King’s College, London as a research assistant
• 1951-1953 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
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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
http://science.education.nih.gov/supplements/nih4/technologyother/glossary.htm
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• 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
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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
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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
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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
http://www.matter.org.uk/diffraction/introduction/what_is_diffraction.htm
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http://search.aol.com/aol/imageDetails?invocationType=imageDetails&query=x-ray+diffraction&img=http%3A%2F%2Fwww.chem.missouri.edu%2Fx-ray%2Fimages%2Fbigmolecule.jpg&site=&host=http%3A%2F%2Fwww.chem.missouri.edu%2Fx-ray%2F&width=99&height=123&thumbUrl=http%3A%2F%2Fimages-partners-tbn.google.com%2Fimages%3Fq%3Dtbn%3A79DKhJNpTqr5lM%3Awww.chem.missouri.edu%2Fx-ray%2Fimages%2Fbigmolecule.jpg&b=image%3Fquery%3Dx-ray%2520diffraction
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X-ray diffraction diagram
http://mrsec.wisc.edu/edetc/modules/xray/X-raystm.pdf
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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
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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 51
http://www.pbs.org/wgbh/nova/photo51/pict-01.html#fea_top
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• 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
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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
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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
www.pbs.org/wgbh/nova/photo51
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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
www.pbs.org/wgbh/nova/photo51
![Page 18: 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)](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649e615503460f94b5c584/html5/thumbnails/18.jpg)
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
![Page 19: 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)](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649e615503460f94b5c584/html5/thumbnails/19.jpg)
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
![Page 20: 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)](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649e615503460f94b5c584/html5/thumbnails/20.jpg)
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
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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 <A>, thymine <T>, cytosine <C>, and guanine <G>)
– 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
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Modeling DNA
• James Watson and Francis Crick modeling DNA structure
http://www.chemheritage.org/classroom/chemach/pharmaceuticals/watson-crick.html
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References (n.d.). X-Ray Diffraction Message posted to
http://www.pbs.org/wgbh/nova/photo51/
(n.d.). Rosalind Elsie Franklin Message posted to http://www.sdsc.edu/ScienceWomen/franklin.html (
n.d.). What is X-Ray Diffraction Message posted to http://www.bioinformatics.nl/webportal/background/xray...
(n.d.). X-Ray DIffraction Message posted to http://science.education.nih.gov/supplements/nih4/tech... (
n.d.). X-Ray Diffraction-FInding the Structure of DNA Message posted to http://www.branta.connectfree.co.uk/x-ray_diffraction.htm
Ardell, D. (2006, Oct. 25). Rosalind Franklin (1920-1958) Message posted to http://www.accessexcellence.org/RC/AB/BC/Rosalind_Fran...
Day, E. & Ross, S. (2004). X-Ray Diffraction Message posted to http://www.nhn.ou.edu/~johnson/Education/Juniorlab/Pre... Diffraction