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Scientists like to actually see the things they research.
But this isn't always possible.
Source: Clipart ETC
Most of what we see is larger than the wavelength of visible light.
Scientists occasionally want to study things that are smaller than
the wavelength of visible light.
Wavelength of ultraviolet light: 400 nanometers
One nanometer = one millionth of a millimeter
Source: Wikipedia
That was the case with the ribosome that Nobel Prize laureate
Prof. Ada Yonath wanted to explore.
The diameter of a ribosome is about 20 nanometers, which is
approximately 20 times smaller than the ultraviolet wavelength.
Wavelength of ultraviolet light: 400 nanometers
One nanometer = one millionth of a millimeter
To "see" the internal structure of bodies the size of a ribosome,
scientists often expose them to x-rays.
This reveals the location of single atoms.
The wavelength of x-rays is about 20 times smaller than the diameter
of ribosomes.
Source: NASA
The ribosome is a key component of living cells.
Source: Wikipedia
Living cells have a single nucleus and thousands of ribosomes.
Source: Wikipedia
Ribosomes translate the genetic information within the cell's
nucleus into a process for producing proteins.
Source Wikipedia
Proteins are huge molecules, structured like folding chains and
composed of a sequence of amino acids.
Source: Wikipedia
Proteins are one of the most important compounds that make up
living organisms. They are found in every living cell.
Ribosomes themselves are composed, in part, of proteins
Source: Clipart ETC
Prof. Ada Yonath and other researchers wanted to know which
proteins are contained in the ribosome and how they are
organized spatially.
To find out, they needed to rely on x-rays.
Source: Prof' Ada Yonaths' Lab
The method for determining the structure of biological molecules
using radiation is called x-ray crystallography.
Prof. Ada Yonath uses x-ray crystallography to study ribosomes.
Source NASA
To prepare a living substance for x-ray crystallography research,
the substance itself needs to be crystallized.
Source: Prof' Ada Yonaths' Lab
Different crystals diffract the x-rays directed at them in different
ways.
The particular composition and spatial structure of each crystal
create a unique picture.
This picture resembles a collection of dots.
Source: Wikipedia
All the pictures created during x-raying are entered into powerful
computers, which feed them into a complex decoding process
resulting in three-dimensional images.
The computer-assisted decoding relies on mathematical
formulas and hypothetical structural models, based on data
gathered through other methods.
Source: Wikipdia
As the x-raying proceeds, it is crucial to maintain the stability of
the substance being examined. In many cases, the substance is
deformed due to the strong radiation it receives, similar to the
way living tissues are harmed in an X-ray test.
Because of the radiation, the substance changes form,
preventing the researcher from determining its structure.
Prof. Ada Yonath was the first to deal successfully with two
complex problems: crystallizing the ribosome and preparing the
crystal for x-ray without changing its form during the examination
process.
Source: L'OREAL-UNESCO Awards For Women in Science
The living substance that Prof. Yonath used to examine
ribosome structure was bacteria that live in hot springs or in the
Dead Sea, which are resistant to high temperatures.
Prof. Yonath cooled samples of the substance to a temperature
of -185º C, preventing its decomposition under experimental
conditions.
This accomplishment earned her the 2009 Nobel Prize for
Chemistry.
She shared the prize with Thomas Steitz of Yale University in
the U.S. and Venkatraman Ramakrishnan of Cambridge
University in Britain.
The three scientists were awarded the prize for their contribution
to the study of ribosome structure and functioning.
Most antibiotic medicines attach themselves to bacterial
ribosomes, preventing them from acting.
By understanding how antibiotics affect ribosomes, scientists
can conduct research leading to the development of more
effective drugs.
Source: The lab of Prof' Ada Yonath
Writing:
Hanan Cohen
Editing:
Nurit Snir
Graphic design: Vadik Bakman
Many thanks to Prof. Ada Yonath for her comments on this presentation