Theoretical conformational analysis was used to study the spatial structure and conformational properties of myelopeptides, bone-marrow peptide mediators. The low-energy conformations of three hexapeptides MP-1 (Phe-Leu-Gly-Phe-Pro-Thr), MP-2 (Leu-Val-Val-Tyr-Pro-Trp), and MP-3 (Leu-Val-Cys-Tyr-ProGln) were found, the values of dihedral angles of the backbone and side chains of the amino acid residues constituting these peptides were determined, and the energies of intra-and interresidual interactions were estimated.

Opioid peptides are currently considered the most studied group of peptide signaling substances. Opium causes pain relief, sedation and falling asleep, as well as a euphoric state and a number of vegetative reactions. Opioid peptides are of animal and plant origin. A number of exogenous peptides obtained from food have opioid-like properties. Such peptides were called exorphins, there are dozens of representatives. The alpha-laktorphine molecule is a representative of this class. The conformational possibilities of the Tyr-Gly-Leu-Phe alpha-lactorphine molecule were studied by the method of theoretical conformational analysis. The potential function of the system is chosen as the sum of non-valence, electrostatic and torsion interactions and the energy of hydrogen bonds. The low-energy conformations of the alpha-laktorphine molecule, the values of the dihedral angles of the main and side chains of the amino acid residues that make up the molecule were found, and the energy of intra- and interresidual interactions was estimated. It was shown that the spatial structure of the alpha-laktorphine molecule can be represented by eleven forms of the main chain. The results obtained can be used to elucidate the structural and structural-functional organization of exorphin molecules.

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The spatial structure of ACTH-(6-9)-PGP molecule has been investigated using theoretical conformational analysis method. Amino acid sequence of the N-terminal pentapeptide fragment of His-Phe-Arg-Trp-Pro of this molecule conforms to the fragment 6-9 of ACTH hormone. Calculations of conformational states of this molecule are carried out regarding nonvalent, electrostatic and torsional interactions and the energy of hydrogen bonds. The spatial structure of the His-Phe-Arg-Trp-Pro-Gly-Pro molecule was estimated on the low–energy conformations of the N-terminal tetrapeptide fragment His-Phe-Arg-Trp and C-terminal tripeptide fragment Pro-Gly-Pro of this molecule. It is shown that the spatial structure of heptapeptide molecule can be presented by 11 low-energy forms of the main chain. The low–energy conformations of this molecule, the values of dihedral angles of the backbone and side chains of the amino acid residues were founded and the energies of intra- and inter-residual interactions were determined.

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