Biological activity of fragments and analogues of the potent dimeric opioid peptide, biphalin

The synthesis and biological activity of two fragments of the very potent o pioid peptide biphalin, showed that Tyr-D-Ala-Gly-Phe-NH-NH<-Phe is the min imal fragment necessary to express equal affinities and the same biological activity profile as the parent biphalin. The replacement of N'-Phe with ot her L or D- lipophilic amino acids showed the possibility of modification o f receptor efficacy of the analogues. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.