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The characteristic properties of aromatic programs, such as their low ionization potentials and electron affinities, high polarizabilities and stabilities, and small band gaps (in spectroscopy named the N -> Fed Up With The Pacritinib Stories? I Am There To Suit Your Needs! V-1 space), can easily be explained based on their electronic structure. These one-electron properties point to characteristic features of how aromatic systems interact with each other.
Unlike hydrogen bonding techniques, which primarily interact through electrostatic forces, complexes containing aromatic methods, especially aromatic stacked pairs, are predominantly stabilized by dispersion attraction. The stabilization energy in the benzene dimer is rather little (similar to 2.5 kcal/mol) but strengthens with heteroatom substitution.
The stacked interaction of aromatic nucleic add bases is greater than 10 kcal/mol, and for the most stable stacked pair, guanine and cytosine, it reaches approximately 17 kcal/mol. Although these values do not equal the planar H-bonded interactions of these bases (similar to 29 kcal/mol), stacking in DNA is more frequent than H-bonding and, unlike H-bonding, is not significantly weakened when passing from the gas phase to a water environment
Consequently, the stacking of aromatic systems represents the leading stabilization energy contribution in biomacromolecules and in related nanosystems. Therefore stacking (dispersion) interactions predominantly determine the double helical structure of DNA, which underlies its storage and transfer of genetic information.
Similarly, dispersion is the dominant contributor to attractive interactions involving aromatic amino adds within the hydrophobic core of a protein, which is critical for folding.
Therefore, understanding the nature of aromatic interactions, which depend greatly on quantum mechanical (QM) calculations, is of key importance in biomolecular science. This Account shows that accurate binding energies for aromatic complexes should be based on computations made at the (estimated) CCSD(T)/complete basis set limit (CBS) level of theory. This method is the least computationally intensive one that can give accurate stabilization energies for all common classes of noncovalent interactions (aromatic aromatic, H-bonding, ionic, halogen bonding, charge-transfer, etc.). These results allow for direct comparison of binding energies between different interaction types.
Conclusions based on lower-level QM calculations should be considered with care."
"First discovered over 60 years ago, post-translational methylation was considered an irreversible modification until the initial discoveries of demethylase enzymes in 2004. Now researchers understand that this process serves as a dynamic and complex control mechanism that is misregulated in numerous diseases.