In two reports in the science journal Nature on Wednesday, researchers describe the structure of small and large subunits of ribosomes -- complex particles that make the thousands of proteins that are needed for every living cell.

``This research is a technical and scientific tour de force,'' said Malcolm Capel, a biophysicist at the US Department of Energy's Brookhaven National Laboratory in New York and a co-author of both studies.

A ribosome reads messenger MRNA (ribonucleic acid) which interacts with transfer RNA and amino acids to build new proteins. It translates the MRNA into chains of amino acids that make up the proteins.

Using a scientific technique called X-ray crystallography, scientists led by Venki Ramakrishnan, formerly of the University of Utah School of Medicine and now at the Medical ResearchCouncil Laboratory of Molecular Biology in Cambridge, England, constructed a model of a ribosome subunit known as 30s from a bacterium called thermus thermophilus.

``Ribosomes are central to biology. Every single cell on earth requires ribosomes to synthesise proteins. It's essential to life on the planet,'' William Clemons, who worked with Ramakrishnan, told Reuters.

Thomas Steitz and his colleagues at Yale University and the Howard Hughes Medical Institute in New Haven, Connecticut, described the structure of the bigger ribosomal subunit called 50s from another bacterium known as haloarcula marismortui. The two subunits work together to generate proteins.

``On a basic science level, these findings represent a giant step on the road to understanding how living organisms make proteins,'' said Capel.

``On a more practical level, many bacterial infections are stopped by antibiotics, which work by inhibiting the production of ribosomes in bacterial cells. Better structural knowledge of ribosomes may leadto developing more effective antibiotics through computer modelling,'' he went on to add.

The findings could also have important industrial applications because ribosomes are used to make enzymes which produce chemical reactions.

Constructing the models was also a technical feat because of the size and complexity of ribosomes. To create the models the researchers grew crystals of ribosomes which gave them molecules that are arranged in repeated patterns. The crystals were frozen to protect them from radiation damage.

Then they penetrated the crystal with an X-ray beam that caused tens of thousands of diffraction spots on an imaging detector.