LE MOLECOLE CHE CURANO

MOLECULES THAT HEAL

In addition to hydrogen and oxygen, other elements are also essential for life, and some are crucial for survival and not perishing from infection or disease. Since ancient times, for example, it had been observed that certain elements had beneficial properties. In ancient Rome, it was said that army officers enjoyed better health than ordinary soldiers because they dined on silver plates. Modern science has confirmed the antiseptic power of silver (Ag) and copper, i.e. the property of preventing or slowing down the growth of microbes. When in contact with these metals, bacteria, fungi, and algae absorb their atoms, suffer serious metabolic damage and suffocate within hours. This property, called ‘oligodynamics’, makes certain metals more sterile than wood and plastic and is the reason why door handles and handrails are made of metal in public spaces. Be careful though, silver is fine as an antiseptic, but it should not be ingested in excess as it colours the skin blue!

However, the most effective medicines available to us today are not simple elements, but complex

compounds.

The history of modern pharmacology begins with the famous Louis Pasteur, a French chemist, and biologist who lived in the 1800s. He noticed a peculiarity of biological molecules, the essence of living matter: their so-called ‘chirality’, i.e. the fact that they appear in the right and left-handed versions, like our hands. Chirality is the property of an object to be non-overlapping with its mirror image. And it has been established that all amino acids, the constituent units of all proteins in our bodies, and proteins in organic matter are ‘left-handed’. Amino acids are therefore asymmetrical molecules that can exist in two forms mirroring each other, the L-form and the D-form. These molecules are equal to each other in everything (same bonds, same atoms), but are one the mirror image of the other. Pasteur realized that proteins synthesized in the human cell only ever use the L- a form of amino acids. This simple property was a great discovery, which also enabled the creation of antibiotic drugs from 1935 onwards.

Pasteur’s discovery defines life: ‘chirality’, according to Pasteur, ‘was the sharp dividing line that can be drawn at present to separate the chemistry of inorganic matter from that of living matter’. The great scientist showed us what the ditch is that separates the chemistry of inert matter from that of life.

The different chirality of molecules implies a different property, and if we get the chirality wrong, we can cause disasters in the body’s levogyric environment. An example of this is thalidomide, a German drug from the 1950s that eliminated morning sickness in pregnant women. It was discovered that the benevolent and healing version of the active ingredient was mixed with one of opposite chirality because during processing the two different types could not be separated. This resulted in many children with congenital deformities being born without arms or legs.

The ability to produce chiral drugs is due to chemist William Knowles, who through his studies on rhodium (Rh) succeeded in constructing a chiral catalyst, i.e. a reaction that could produce molecules with the right chirality. It was 1968 and we can consider this the birth year of modern pharmaceutical chemistry. This discovery, which makes us realize how the simple elements of the Periodic Table never cease to amaze us, earned Knowles the Nobel Prize in 2001.