Why Nature Chose Selenium

Area of Science:

• Biochemistry
• Bioinorganic Chemistry
• Chemical Biology

Background:

• Celebrates the bicentennial of selenium's discovery by Jöns Jacob Berzelius.
• Inspired by Frank Westheimer's work on the biological chemistry of phosphates.
• Examines selenium's role in biological processes, comparing it to sulfur.

Purpose of the Study:

• To explore why nature selected selenium for specific biological functions.
• To compare the chemical properties of selenium and sulfur in biological contexts.
• To elucidate the redox chemistry differences driving selenium's unique roles.

Main Methods:

• Historical review of selenium's biological discoveries.
• Comparative chemical analysis of selenium and sulfur.
• Discussion of redox reactions and bonding characteristics (e.g., pi bonds).

Main Results:

• Redox chemistry represents the most significant difference between selenium and sulfur.
• Selenium's inability to form strong pi bonds and loosely held valence electrons influence its reactivity.
• Selenium's unique properties allow biomolecules to resist permanent oxidation, offering a functional advantage.

Conclusions:

• Selenium's distinct redox properties, particularly its behavior in oxidation-reduction reactions, explain its biological selection.
• The replacement of sulfur with selenium in biomolecules confers resistance to irreversible oxidation.
• This 'gain of function' is exemplified by various biological systems discussed in the literature.