10.1021/ja063174a.s001 Markus Heller Markus Heller Martin Sukopp Martin Sukopp Natia Tsomaia Natia Tsomaia Michael John Michael John Dale F. Mierke Dale F. Mierke Bernd Reif Bernd Reif Horst Kessler Horst Kessler The Conformation of <i>cyclo</i>(−d-Pro−Ala<sub>4</sub>−) as a Model for Cyclic Pentapeptides of the dL<sub>4</sub> Type American Chemical Society 2006 dL 4 TypeThe conformation Cyclic Pentapeptides intramolecular distances bioactive compounds NMR results hydrogen bonds relaxation behavior cyclo bioactive conformations MD simulations cyclic peptide NMR techniques 2006-10-25 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/The_Conformation_of_i_cyclo_i_d_Pro_Ala_sub_4_sub_as_a_Model_for_Cyclic_Pentapeptides_of_the_dL_sub_4_sub_Type/3051937 The conformation of the cyclic pentapeptide <i>cyclo</i>(−d-Pro−Ala<sub>4</sub>−) in solution and in the solid state was reinvestigated using modern NMR techniques. To allow unequivocal characterization of hydrogen bonds, relaxation behavior, and intramolecular distances, differently labeled isotopomers were synthesized. The NMR results, supported by extensive MD simulations, demonstrate unambiguously that the preferred conformation previously described by us, but recently questioned, is indeed correct. The validation of the conformational preferences of this cyclic peptide is important given that this system is a template for several bioactive compounds and for controlled “spatial screening” for the search of bioactive conformations.