This project:

Project Objective:    To determine the distance/angle dependence of CH-p interactions using a molecular torsion balance.

	Significance:    CH-p interactions have been proposed to be important inter-molecular forces, especially in peptides containing aromatic groups. An example at left shows a folded structure for N-phenylacetyl-L-Phe. (Fig. 1)
Figure 1. N-phenylacetyl-L-Phe

Progress: A molecular torsion balance was successfully used by our lab to measure CH-p interactions.(Ref 1,2 and Fig. 2)
	Figure 2. Tröger's base derivative.

A similar torsion balance was synthesized to determine the distance/angle dependence of CH-p interactions. (Fig. 3)
	Figure 3. Ethanoanthacene derivative.

Conclusion: The ethanoanthracene molecule prefers the unfolded conformation, but the Tröger's base molecule folds. Because the hinge angle is larger for the ethano-anthracene, the folded conformer fails to achieve favorable contacts. These results demonstrate how CH-p interactions are sensitive to subtle changes in distances.

References: 1. S. Paliwal, S. Geib, and C. S. Wilcox "A Molecular Torsion Balance for Weak Molecular Forces. Effects of Tilted-T Edge-to-Face Aromatic Interactions on Conformational Selection and Solid State Structure." J. Amer. Chem. Soc. 1994 116, 4497-4498. 2. C. S. Wilcox, S. Paliwal, E. Kim "Measurements of Molecular Electrostatic Field Effects in Edge-to-Face Aromatic Interactions and CH-p Interactions with Implications for Protein Folding and Molecular Recognition." J. Amer. Chem. Soc., 1998 120, 11192-11193.

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