Franklin, Rosalind
Francium
27°C
BOILING POINT: 677°C
DENSITY: unknown
MOST COMMON ION: Fr
MELTING POINT:
The element francium is named for the country of France and its most stable isotope is known as actinium K. Dimitri Mendeleev assigned it the name
eka-cesium prior to its actual discovery, although at this time it was also
known as russium, virginium, and moldavium. Marguerite Perey, a one-time
assistant of Marie Curie, discovered francium in 1939. It is not found in its
elemental state and less than one ounce is thought to exist in Earth’s crust
at any one time.
Although there are a number of isotopes of francium, most decay very
rapidly to other elements. Most isotopes with masses of 223 AMU and lower
emit -particles (consisting of two protons and two neutrons) to become
astatine. Some low mass francium isotopes can also undergo electron capture (the conversion of a proton to a neutron through the absorption of an
electron) to become radon. Francium isotopes with masses of 220 AMU and
higher can undergo -decay (the conversion of a neutron to a proton through
the emission of an electron) to become radium. Francium-223 is the most
stable isotope and has a half-life of 21.8 minutes.
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Fr
FRANCIUM
223
isotope: form of an atom that differs by
the number of neutrons in the nucleus
-particle: subatomic particle with 2
charge and mass of 4; a He nucleus
Naturally occurring francium is the product of a side reaction of the decay pathway of actinium. Actinium-227 generally undergoes -decay to produce thorium-227, but about 1 percent of the actinium emits an -particle
to form francium-223. Francium can be produced in the laboratory via proton bombardment of thorium and during oxygen 18 (O-18) bombardment
of heated gold.
Because of its extremely low abundance, short half-life, and high radioactivity, neither francium nor its compounds have economic applications.
S E E A L S O Alkali Metals; Curie, Marie Sklodowska; Mendeleev, Dimitri; Radioactivity.
Nathan J. Barrows
Bibliography
Heiserman, David L. (1992). Exploring Chemical Elements and Their Compounds. Blue
Ridge Summit, PA: Tab Books.
Lide, David R., ed. (2000). CRC Handbook of Chemistry & Physics, 81st edition. New
York: CRC Press.
Franklin, Rosalind
ENGLISH MOLECULAR BIOLOGIST
1920–1958
Rosalind Elsie Franklin, the second of four children and the first daughter
of Ellis Franklin, a wealthy Jewish banker, and Muriel Franklin (née Waley), was born on July 25, 1920, in London. Although raised in a happy
home where children were encouraged to develop their individuality, Rosalind felt discriminated against because she was a girl, a feeling that surfaced
again, along with an awareness of anti-Semitism, when she was working on
DNA at King’s College.
DNA: deoxyribonucleic acid—the natural
polymer that stores genetic information in
the nucleus of a cell
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Franklin, Rosalind
In 1938 Franklin graduated from St. Paul’s Girls’ School in London,
where, at age fifteen, she decided to become a scientist. Although her father disapproved of college education for women, she attended Newnham
College, a women’s college at Cambridge University, from which she received a bachelor’s degree in 1941. She spent a year (1941–1942) working
with future (1967) Nobel chemistry laureate Ronald George Wreyford Norrish, after which she contributed to the World War II effort by working as
a physical chemist for the British Coal Utilization Research Association
(1942–1945). Her research on the structural changes caused by heating coal
resulted in five publications, earned her a doctorate, and made her a recognized authority on crystallography and industrial chemistry.
English biophysicist Rosalind Franklin,
who made important studies in the
structure of DNA.
monoclinic: one of several arrangements
of atoms found in crystalline solids;
characterized by a unit cell of three axes
each of a differing length; two axes are
mutually perpendicular while the third is
at an oblique angle
Franklin’s next three years (1947–1950) were spent as a research scientist at the Laboratoire Central des Services Chimiques de l’État in Paris.
She became a researcher at King’s College, London, in 1951, where she began to work on the structure of deoxyribonucleic acid (DNA), the physical
basis of heredity. Her relationship with DNA coworker Maurice Hugh Frederick Wilkins (b. 1916), a biophysicist from New Zealand, soon degenerated into one of mutual dislike. In England two laboratories were working
on the crystalline structures of biological materials: King’s College was
working on DNA, and the Cavendish Laboratory in Cambridge was working on proteins. The American James Dewey Watson (b. 1928) and the
Briton Francis Harry Compton Crick (b. 1916) decided that DNA research
was more exciting than the protein research in which they were thought to
be engaging at the Cavendish.
Franklin discovered that DNA occurs in two forms (the “A” form, which
is more crystalline, contains more water than the “B” form, which is the
form that occurs in cells). When Watson and Crick visited King’s, Wilkins
showed them Franklin’s x-ray diffraction photographs of the “B” structure.
Her critique of Watson and Crick’s earlier work helped them reformulate
their structure. However, she failed to recognize the significance of the particular crystal symmetry system (monoclinic C2 symmetry) of “B” DNA.
Crick, who was working on hemoglobin, which possessed C2 symmetry,
recognized that this meant that the strands of nucleic acid are antiparallel,
so they could serve as templates for each other. This insight, together with
Watson’s knowledge of Erwin Chargaff’s base pairing, led to their final success. Watson, Crick, and Wilkins received the Nobel Prize in physiology or
medicine in 1962.
Watson and Crick wished to publish quickly, before Linus Pauling, but
were embarrassed that all the experimental work had been performed at
King’s, and Franklin’s data had not been published. The heads of King’s
and the Cavendish approached the editors of Nature, who agreed to publish three articles in a single issue (April 25, 1953).
Watson and Crick’s short paper was followed by an analysis by Wilkins,
A. R. Stokes, and H. R. Wilson of the x-ray crystallographic data and
Franklin and her graduate student Raymond G. Gosling’s conclusion that
the phosphate backbone of DNA lies on the outside of the structure. The
Watson and Crick paper provided the experimental evidence for the helical structure of nucleic acids. Actually, Franklin and Gosling’s paper provided the basis for Watson and Crick’s structure, rather than being a
confirmation of it.
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Freons
Because Franklin and Wilkins were hardly speaking to each other,
Franklin left King’s College in 1953 for Birkbeck College, also in London,
where she finished her DNA work and became head of the team studying
tobacco mosaic virus. Franklin died of ovarian cancer on April 16, 1958, at
the age of 37. S E E A L S O Deoxyribonucleic Acid (DNA); Double Helix;
Pauling, Linus; Watson, James Dewey.
George B. Kauffman
Bibliography
Chemistry & Industry (2003). “Rosalind Franklin: The Woman behind the DNA Helix” Chemistry & Industry 8 (April 21):13.
Elkin, Lynne Osman (2003). “Rosalind Franklin and the Double Helix.” Physics Today 56 (March):42.
Harvey, Joy, and Ogilvie, Marilyn B. (2000). “Rosalind Elsie Franklin (1920–1958).”
In The Biographical Dictionary of Women in Science: Pioneering Lives from Ancient
Times to the Mid-20th Century, Vol. 1, ed. Marilyn Ogilvie and Joy Harvey. New
York and London: Routledge.
Julian, M. M. (1983). “Rosalind Franklin, from Coal to DNA to Plant Viruses.” Journal of Chemical Education 60:660–662.
Klug, Aaron (1968). “Rosalind Franklin and the Discovery of the Structure of DNA.”
Nature 219:808–810, 843–844.
Maddox, Brenda (2002). Rosalind Franklin: The Dark Lady of DNA. New York: HarperCollins Publishers.
McGrayne, Sharon Bertsch (1998). Nobel Prize Women in Science: Their Lives, Struggles, and Momentous Discoveries, 2nd edition. Washington, DC: Joseph Henry Press.
Miksic, Mary Clarke (1993). “Rosalind Elsie Franklin (1920–1958).” In Women in
Chemistry and Physics: A Biobibliographic Sourcebook, ed. Louise S. Grinstein, Rose
K. Rose, and Miriam Rafailovich. Westport, CT, and London: Greenwood Press.
Olby, Robert (1972). “Rosalind Elsie Franklin (1920–1958).” In Dictionary of Scientific Biography, Vol. 5, ed. Charles Coulston Gillispie. New York: Scribner.
Rayner-Canham, Marelene, and Rayner-Canham, Geoffrey (1998). Women in Chemistry: Their Changing Roles from Alchemical Times to the Mid-Twentieth Century.
Washington, DC: American Chemical Society.
Sayre, Anne (1975). Rosalind Franklin and DNA. New York: W.W. Norton & Co.
Watson, James D. (1968). The Double Helix: A Personal Account of the Discovery of DNA.
New York: Atheneum.
Internet Resources
Franklin, Rosalind, and Gosling, Raymond G. (1953). “Molecular Configuration in
Sodium Thymonucleate.” Nature 171:740–741. Available from http://www.nature
.com/nature/dna50/franklingosling.pdf.
“NOVA: Secret of Photo -51.” PBS Online. Available from http://www.pbs.org/wgbh
/nova/photo51.
Freons
The trademark Freon refers to any of several gaseous chlorofluorocarbons,
CFCs, with the general formula CFxCl4x or C2FxCl6x. Due to their physical and chemical properties, these CFCs became the compounds of choice
as propellants and refrigerants, substituting for the toxic and flammable sulfur dioxide and ammonia materials used until the early 1930s. Due to their
long life, Freons drift for years in the atmosphere and eventually find their
way to the stratosphere where they decompose and destroy the protective
ozone layer. Current legislation calls for the elimination of Freons.
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