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)
Accomplishments
• 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 Xray diffraction techniques
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
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
• 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
http://www.matter.org.uk/diffraction/introduc
tion/what_is_diffraction.htm
http://search.aol.com/aol/imageDetails?invocationType=imageDetails&query=xray+diffraction&img=http%3A%2F%2Fwww.chem.missouri.edu%2Fxray%2Fimages%2Fbigmolecule.jpg&site=&host=http%3A%2F%2Fwww.chem.missouri.edu%2Fxray%2F&width=99&height=123&thumbUrl=http%3A%2F%2Fimages-partnerstbn.google.com%2Fimages%3Fq%3Dtbn%3A79DKhJNpTqr5lM%3Awww.chem.missouri.edu%2Fxray%2Fimages%2Fbigmolecule.jpg&b=image%3Fquery%3Dx-ray%2520diffraction
X-ray diffraction diagram
http://mrsec.wisc.edu/edetc/modules/xray/
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 51
http://www.pbs.org/wgbh/nova/photo51/pict01.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
www.pbs.org/wgbh/nova/photo51
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
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 <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
Modeling DNA
• James Watson and
Francis Crick
modeling DNA
structure
http://www.chemheritage.org/classroom/ch
emach/pharmaceuticals/watson-crick.html
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