MIF-1 and Tyr-MIF-1 analogues containing unnatural amino acids: synthesis, biological activity and docking studies.

Melanocyte-inhibiting factor (MIF-1) is the first hypothalamic tripeptide which has been demonstrated to act not only in the brain but also in the pituitary. Tyr-MIF-1 acts as an opiate agonist. It binds selectively and with a high affinity to the μ-opioid receptor when compared with the δ-and κ-opioid receptors. A large number of analogues of MIF-1 and Tyr-MIF-1, containing various modifiers in their structures, have been synthesized and their analgesic effect was determined by various in vivo tests. The aim of current study was: (1) to synthesize new MIF-1 and Tyr-MIF-1 analogues containing sulfoarginine (sArg) and norsulfoarginine (NsArg) in the second and third position, respectively; (2) with the help of docking procedures to find the relationship between structure and biological activity of MIF-1 and Tyr-MIF-1 analogues previously synthesized and biologically tested; (3) using found correlation to predict the biological effect of newly synthesized analogues. New analogues of MIF-1 and Tyr-MIF-1 were synthesized using methods of peptide synthesis in solution. Docking was performed with GOLD 5.0 and a correlation between the obtained docking data and the values from in vivo test was found. Some structure-activity relationships were determined. According to the correlation, we made assumptions about the biological effect of sArg and NsArg containing MIF-1 and Tyr-MIF-1. A computational approach could be very useful in the elucidation of the structure-activity relationship and in the design of new analogues with desired biological effect. [ABSTRACT FROM AUTHOR]