page_title: Stacking (chemistry)
section_title: Applications
hierarchical_section_title: Stacking (chemistry) / Applications
caption_attribution_description: English: Crystal structure of Tacrine bound to acetylcholinesterase (PDB accession: 1ACJ) visualized using USCF Chimera. A pi stacking interaction between Tacrine (blue) and Trp84 (red) is proposed.
context_page_description: In chemistry, pi stacking refers to attractive, noncovalent interactions between aromatic rings, since they contain pi bonds. These interactions are important in nucleobase stacking within DNA and RNA molecules, protein folding, template-directed synthesis, materials science, and molecular recognition, although new research suggests that pi stacking may not be operative in some of these applications. Despite intense experimental and theoretical interest, there is no unified description of the factors that contribute to pi stacking interactions.
context_section_description: A powerful demonstration of stacking is found in the buckycatcher. This molecular tweezer is based on two concave buckybowls with a perfect fit for one convex fullerene molecule. Complexation takes place simply by evaporating a toluene solution containing both compounds. In solution an association constant of 8600 M⁻¹ is measured based on changes in NMR chemical shifts.
  Pi stacking is prevalent in protein crystal structures, and also contributes to the interactions between small molecules and proteins. As a result, pi–pi and cation–pi interactions are important factors in rational drug design. One example is the FDA-approved acetylcholinesterase (AChE) inhibitor tacrine which is used in the treatment of Alzheimer's disease. Tacrine is proposed to have a pi stacking interaction with the indolic ring of Trp84, and this interaction has been exploited in the rational design of novel AChE inhibitors.
caption: Tacrine bound to acetylcholinesterase (PDB 1ACJ). A pi stacking interaction between tacrine (blue) and Trp84 (red) is proposed.
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