The 2009 Nobel Prize for Chemistry was awarded on October 7, to three scientists whose work has been to elucidate the atomic structure and function of the ribosome.
The awardees are: Venkatraman Ramakrishnan, Medical Research Council Laboratory of Molecular Biology in Cambridge, UK; Thomas Steitz, Yale University; and Ada Yonath, Weizmann Institute of Science , Rehovot, Israel (1).
Their research has focused on the use of x-ray crystallographic imaging. And though the subject of the chemistry award has been criticized by some as more biology than chemistry, this biology graduate needed to do some research to understand the technique behind the award. Here is some basic information, sort of an x-ray crystallography 101.
Crystals have been around much longer than x-rays. And crystallographers have long known that crystals are made of an orderly arrangement of atoms. The angles of the crystals are instructive about this orderly atomic arrangement. The advent of x-rays allowed development of a powerful tool for determining a crystals structure and cell size, that tool being x-ray crystallography (2).
It is impossible to view atoms with visible light, using even the most powerful microscope. In order for an object to be seen, its size needs to be at least half the wavelength of the light source being used. The distance between atoms is far too short to view with visible light (3).
However, x-rays have a wavelength similar in length to the distance between two atoms. When x-rays are “beamed” at a crystal, the electrons of the crystal’s atoms diffract the x-rays, resulting in a pattern that can be mathematically transformed into electron density maps. And because electrons surround atoms in a relatively uniform manner, these density maps show where the atoms are located (3).
To get a three dimensional structure, a crystal is then rotated while a computerized detector makes a two–dimensional density map for each angle of rotation; the third dimension comes from a comparison of these images to the crystal’s rotation (3). These three dimensional structures allow researchers to identify precise molecular locations, for instance, binding sites.
But the ribosome…what about the ribosome?
X-ray crystallography, in the hands of these experts, has allowed visualization of the atomic structure of the ribosome. In research cited for the 2009 Chemistry Nobel Prize, the three researchers have reported crystal structures that show antibiotics binding sites on ribosomes (1).
The practical use of this information is powerful. Ribosomes are protein-producing powerhouses, present in all cells. We know that humans as well as bacteria need to produce protein to live. Say a person finds or creates an antibiotic that binds to a bacterial ribosome in such a manner that the ribosome can no longer produce protein.
Voila–bacterial death. Yet ribosomes in our cells differ from bacterial ribosomes and so are not harmed (4).
What the Chemistry Nobelists have accomplished is to make ribosome structure, and thus binding locations identifiable. Leading to the discovery of life-saving antibiotics.
- Nobel Prize for chemistry of life. BBC News online. Retrieved 8-Oct-2009.
- X-ray crystallography, Tulane University. Retrieved 8-Oct-2009.
- X-ray crystallography, St. Olaf University. Retrieved 8-Oct-2009.
- M.W. Gray, D. Sankoff, R.J. Cedergren (1984) Nucleic Acids Res. 12,5837–52. PMID: 6462918