Protegrin pore formation is believed to occur in a stepwise fashion that begins with a nonspecific peptide interaction with the negatively charged bacterial cell walls via hydrophobic and positively charged amphipathic surfaces. There are five known nature protegrins (PG1-PG5), and early studies of PG-1 (PDB ID:1PG1) shown that it could form antiparallel dimer in membrane mimicking environment which could be a first step for further oligomeric membrane pore formation. Later, we solved PG-2 (PDB ID:2MUH) and PG-3 (PDB ID:2MZ6) structures in the same environment and for PG-3 observed a strong d NOE effects between residues R18 and F12, V14, and V16. These "inconsistent" with monomer structure NOEs appears due to formation of an additional antiparallel β-sheet between two monomers. It was also suggested that there is a possible association of protegrins dimers to form octameric or decameric β-barrels in an oligomer state. In order to investigate a more detailed oligomerization process of protegrins, in the present article we report the monomer (PDB ID: 2NC7) and octamer pore structures of the protegrin-5 (PG-5) in the presence of DPC micelles studied by solution NMR spectroscopy. In contrast to PG-1, PG-2, and PG-3 studies, for PG-5 we observed not only dimer NOEs but also several additional NOEs between side chains, which allows us to calculate an octamer pore structure of PG-5 that was in good agreement with previous AFM and PMF data.

The structure and intramolecular transformations of N-phenyl-N`-(diisopropoxythiophosphoryl)-thiourea in (CD 3 ) 2 CO solution were studied by 1 H, 13 C, and 31 P NMR spectroscopy. Combined analysis of NMR data and model calculations gave evidence in favor of high conformational and tautomeric flexibility of the thioureas in solution. The Z,E conformation of the amide form with the two N3H bonds cis and trans to the C=S bond was found to be preferred. Isomeric (thio)ureas are characteristically prone to various conformational transformations which have repeatedly investigated by means of NMR spectroscopy [237]. For example, 1,3-disubstituted thioureas can form 4 rotational isomers. ; = o =; S R 1 R 2 9 9 N N ; = o =; S R 1 9 9 N N R 2 ; = o =; S R 2

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