Purpose of aromatic rings in biochemistry?

[jackmell]

May I ask what are some of the reasons we see so much aromatic, hetrocyclic chemistry in biology? I realize that several amino acids are aromatic and so to nucleic acids, other biomolecules. What exactly do the aromatic rings bring to biology in order for us to see it so profusely utilized?

 

[Yanick]

In DNA the pi electrons of the nitrogenous bases stabilize the helical structure by pi-stacking interactions.

Many proteins which work through radical Chemistry form transient tyrosine and/or tryptophan radicals.

Also there are cofactors for redox Chemistry known as flavins (see FAD/FADH₂) which are integral parts of electron transport processes owing to their ability to do single electron Chemistry and due to their aromaticity in the fully oxidized form.

These are all I could come up with off the top of my head.

 

[Ygggdrasil]

1. Because these compounds gain so much stabilization through their conjugated pi systems (i.e. they are resonance stabilized), it may be easier for the body to synthesize aromatic compounds over other molecules of similar complexity. This stability may also increase their halflives within the organism, making them less prone to degradation (important, for example, for DNA).

2. In binding reactions between two biomolecules, there are two important factors influencing the strength of binding: the enthalpy change (ΔH) of the interaction and the entropy change (ΔS) of the interaction. While many think of the enthalpy of the interaction (how strong are the intermolecular bonds between two interacting molecules), the entropy of the interaction is just as important. Molecules that are conformationally flexible in the free state lose a considerable amount of energy upon binding to their target as this binding usually locks the molecule into a single conformation. Aromatic rings are nice in this regard because they are already conformationally locked and will not lose as much entropy upon binding.

3. As Yanick mentioned, aromatic rings can aid intermolecular interactions on the enthalpy side as well. A number of fairly strong intermolecular interactions involve aromatic rings, including pi-pi stacking interactions and cation-pi interactions.

4. The conjugated pi systems in aromatic rings are great for helping to delocalize charges and radicals. As Yanick mentioned, this property allows the aromatic rings to facilitate a number of chemical reactions.

 

[jackmell]

Hi guys, thanks!

I like the entropy argument: small change in entropy with rings easier than one which creates lots of order as in locking conformations in a flexible molecule, and I like the association with hydrogen bonding used profusely in the reversible-reactions of biochemistry.

 

[LudusRex]

The presence of aromatic rings in biochemistry is crucial for several reasons. First and foremost, aromatic rings provide structural stability to biomolecules. This is due to the strong covalent bonds within the ring, which make it resistant to chemical and biological degradation. This structural stability is essential for the proper functioning of biomolecules in living organisms.

In addition, aromatic rings play a crucial role in the recognition and binding of molecules in biological processes. For example, the shape and chemical properties of aromatic rings allow them to interact with specific receptors and enzymes, thereby regulating important biological processes such as cell signaling and metabolism.

Moreover, aromatic rings are also involved in the transport of molecules across cell membranes. The hydrophobic nature of aromatic rings allows them to easily pass through the lipid bilayer of cell membranes, facilitating the transport of important molecules in and out of cells.

Furthermore, the presence of aromatic rings in biomolecules also contributes to their unique chemical and physical properties. For instance, the conjugated double bonds in aromatic rings make them highly reactive, allowing them to participate in a variety of biochemical reactions.

Overall, the abundance of aromatic and heterocyclic chemistry in biology can be attributed to the diverse roles these rings play in the structure, function, and regulation of biomolecules. Their unique properties make them essential components of many biological processes and contribute to the complexity and diversity of living organisms.