R. Polt, F. Porreca, L. Z. Szabo, E. J. Bilsky, P. Davis, T. J. Abbruscato, T. P. Davis, R. Horvath, H. I. Yamamura and V. J. Hruby, “Glycopeptide Enkephalin Analogs Produce Analgesia in Mice—Evidence for Penetration of the Blood-Brain-Barrier,” Proceedings of the National Academy of Sciences of the USA, Vol. 91, No. 15, 1994, pp. 7114-7118. doi:10.1073/pnas.91.15.7114

has been cited by the following article:

• TITLE: Synthesis and Plasma Stability of Disulfide-Bridged Cyclic Endomorphin-1 Derivatives

  AUTHORS: Friederike M. Mansfeld, Istvan Toth

  KEYWORDS: Endomorphin-1; Opioid Peptide; Cyclisation; Disulfide

  JOURNAL NAME: International Journal of Organic Chemistry, Vol.2 No.1, March 15, 2012

  ABSTRACT: Endomorphin-1 is an endogenous opioid peptide that mediates pain relief through interaction with the μ-opioid receptor in the central nervous system. To enhance the metabolic stability of this tetrapeptide, cyclisation through the formation of a disulfide bridge between the side chains of cysteine residues added to the sequence was explored. A further increase in stability was achieved through N-terminal modification with lipoamino acid and lactose succinamic acid, and the inclusion of D-amino acids. The latter also provided an alternative spatial arrangement of the aromatic side chains. The lipidated cyclic derivatives were insoluble in aqueous buffer, however, the cyclic peptides and glycopeptides showed greatly improved stability towards enzymatic degradation in human plasma.