Interaction of a highly potent dimeric enkephalin analog, biphalin, with model membranes

Marek Romanowski, Xiaoyun Zhu, Varadarajan Ramaswami, Aleksandra Misicka, Andrzej W. Lipkowski, Victor J. Hruby, David F. O'Brien

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Biphalin, (Tyr-D-Ala-Gly-Phe-NH)2, is a highly potent dimeric analog of enkephalin. Its analgesic efficacy is due in Dart to its ability to permeate the blood-brain barrier. To aid in understanding the mechanism of the transmembrane movement we determined and analyzed the permeability and partition coefficients of biphalin and a series of analogues where F, Cl, I, NO2, or NH2 were placed in the para position of the aromatic rings of Phe4,4'. Liposomes composed of neutral phospholipids and cholesterol were used as the model membrane. The overall good correlation between permeability and water-membrane partition coefficients suggests that the movement of biphalins across the model membrane is controlled by diffusion and depends on the water-membrane partition coefficient. To explain the observed correlation between permeability and the electron withdrawing/donating character of the substituents in the phenylalanine ring, we examined various folding patterns of Leu-enkephalin, an endogenous pentapeptide that exhibits affinities toward the same classes of opioid receptors (δ and μ). The observed permeabilities and partition coefficients of biphalin and analogues, as well as the tyrosine side chain accessibility, are consistent with the presence of the type of folding where the tyrosine and phenylalanine side chains are in a close contact. We propose that the aromatic ring interaction can promote the peptide permeability by stabilizing a more compact structure of biphalin that would minimize the number of hydrogen bonds with water and therefore enhances partitioning into the model membrane.

Original languageEnglish (US)
Pages (from-to)245-258
Number of pages14
JournalBiochimica et Biophysica Acta - Biomembranes
Issue number2
StatePublished - Oct 23 1997


  • Blood-brain barrier
  • Drug design
  • Lipid membrane
  • Opioid peptide
  • Partitioning
  • Permeability

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


Dive into the research topics of 'Interaction of a highly potent dimeric enkephalin analog, biphalin, with model membranes'. Together they form a unique fingerprint.

Cite this