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X-ray Crystallography
 Isabella Karle is a
true pioneer of physical chemistry, who invented new methods, using first electron
and then x-ray diffraction, to study the structure of molecules.
Karle was quite a precocious child, whose love of science had, before her
23rd birthday, translated into a BS (1941), MS (1942) and PHD (1944) in physical
chemistry from the University of Michigan.
While at Michigan, she married her fellow chemistry grad student Jerome Karle.
The couple worked briefly on the Manhattan Project at the University
of Chicago (1943), before returning to Ann Arbor, where Isabella became
the first female member of the chemistry faculty. In 1946, they transferred
together to the Naval Research Laboratory
(NRL) in Washington, DC.
Jerome Karle was using complex mathmatics to develop "direct methods" for
analyzing the structure of crystals --- work that would later win him the
Nobel Prize in chemistry (1985). Isabella Karle
began working in chemical analysis by electron diffraction, and invented a superior
apparatus to perform the process. However, she also taught herself x-ray crystallography
from textbooks, so that she could invent practical applications for her husband's
theories, which were being received with some skepticism. In 1963, she published
her "Symbolic Addition Procedure," which used x-ray analysis to determine essentially
equal-atom crystal and molecular structures.
When scientists bombard a crystal with x-rays,
the beam scatters ("diffracts") in a pattern determined by the distances and
angles between its atoms. The method works reliably only if the x-rays' wavelength
and the intervals between atoms are about the same. Isabella Karle's improved
process vindicated her husband's direct method theory; drastically improved
the speed and accuracy of chemical and biomedical analysis; and remains the
basis of all advanced x-ray
crystallography, including computerized programs, used around the world
today. Thanks to Karle's process, the number of new molecular analyses published
annually skyrocketed from about 150 to over 10,000.
By an equally revolutionary three-dimensional modeling process, Karle has
identified and elucidated the structures of hundreds of important molecules.
She was the first to publish the structure of many complex organic and inorganic
substances, including steroids, alkaloids, toxins, ionophores, and especially
peptides (amino acid compounds). With a pattern of these molecules' structure
in front of them, researchers in organic and synthetic chemistry are able to
move forward with much greater speed and confidence.
Isabella Karle continues to serve at NRL, as Chief Scientist of its X-ray
Diffraction Section. (Jerome Karle continues as Chief Scientist of its Structure
of Matter Lab.) Although she did not share her husband's Nobel Prize, Karle
did receive the Swedish Royal Academy of Sciences' Aminoff Prize (1988). Her
other honors have included Women in Science and
Engineering's Lifetime Achievement Award (1986), the Franklin
Institute's Bower Award (1993), and the National
Medal of Science (1995).
[Aug. 2000]
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