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==NMR STUDY OF THE BACKBONE CONFORMATIONAL EQUILIBRIA OF SANDOSTATIN, TWO REPRESENTATIVE MINIMUM ENERGY PARTIALLY HELICAL STRUCTURES==
<StructureSection load='2soc' size='340' side='right'caption='[[2soc]]' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2soc]] is a 1 chain structure. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2SOC OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2SOC FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Solution NMR</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=DPN:D-PHENYLALANINE'>DPN</scene>, <scene name='pdbligand=DTR:D-TRYPTOPHAN'>DTR</scene>, <scene name='pdbligand=THO:REDUCED+THREONINE'>THO</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=2soc FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2soc OCA], [https://pdbe.org/2soc PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2soc RCSB], [https://www.ebi.ac.uk/pdbsum/2soc PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2soc ProSAT]</span></td></tr>
</table>
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== Publication Abstract from PubMed ==
This paper reports a detailed conformational analysis by 1H NMR (DMSO-d6, 300 K) and molecular modeling of the octapeptide D-Phe1-Cys2-Phe3-D-Trp4-Lys5-Thr6-Cys7+ ++-Thr8-ol (disulfide bridged) known as sandostatin (or SMS 201-995 or octreotide) with both somatostatin-like and opioid-like bioactivities. This is the initial report on sandostatin showing that attempts to explain all NMR data using a single average conformation reveal several important inconsistencies including severe violations of mutually exclusive backbone-to-backbone NOEs. The inconsistencies are solved by assuming an equilibrium between antiparallel beta-sheet structures and conformations in which the C-terminal residues form a 3(10) helix-like fold (helical ensemble). This conformational equilibrium is consistent with previous X-ray diffraction investigations which show that sandostatin can adopt both the beta-sheet and the 3(10) helix-like secondary structure folds. In addition, indications of a conformational equilibrium between beta-sheet and helical structures are also found in solvent systems different from DMSO-d6 and for other highly bioactive analogs of sandostatin. In these cases a proper multiconformational NMR refinement is important in order to avoid conformational averaging artifacts. Finally, using the known models for somatostatin-like and opioid-like bioactivities of sandostatin analogs, the present investigation shows the potentials of the proposed structures for the design of novel sandostatin-based conformationally restricted peptidomimetics. These analogs are expected to refine the pharmacophore models for sandostatin bioactivities.

Multiconformational NMR analysis of sandostatin (octreotide): equilibrium between beta-sheet and partially helical structures.,Melacini G, Zhu Q, Goodman M Biochemistry. 1997 Feb 11;36(6):1233-41. PMID:9063871<ref>PMID:9063871</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 2soc" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Large Structures]]
[[Category: Goodman M]]
[[Category: Melacini G]]
[[Category: Zhu Q]]