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Conformational analysis of endomorphin-2 analogs with phenylalanine mimics by NMR and molecular modeling.

Shao X, Gao Y, Zhu C, Liu X, Yao J, Cui Y, Wang R

State Key Laboratory of Applied Organic Chemistry, Institute of Biochemistry and Molecular Biology, School of Life Science, Lanzhou University, Lanzhou 730000, People's Republic of China.

We investigated a series of conformations of endomorphin-2 (EM-2) analogs substituted by phenylglycine (Phg) and homophenylalanine (Hfe) in the position 3 or 4 by two-dimensional (1)H NMR spectroscopy and molecular modeling. Evaluating the aromatic interactions and the dihedral angles in these phenylalanine mimics, we have observed that the conformations in trans isomer have varied from extended to folded as bioactivity decreases. It is suggested that the flexibility of aromatic side chain affects the backbone of EM-2 to adopt folded structures, which may block the ligands in binding to micro-opioid receptor.

Published 10 April 2007 in Bioorg Med Chem, 15(10): 3539-47.
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