Peptide aromatic interactions modulated by fluorinated residues: Synthesis, structure and biological activity of Somatostatin analogs containing 3-(3',5'difluorophenyl)-alanine

Sci Rep. 2016 Jun 7:6:27285. doi: 10.1038/srep27285.

Abstract

Somatostatin is a 14-residue peptide hormone that regulates the endocrine system by binding to five G-protein-coupled receptors (SSTR1-5). We have designed six new Somatostatin analogs with L-3-(3',5'-difluorophenyl)-alanine (Dfp) as a substitute of Phe and studied the effect of an electron-poor aromatic ring in the network of aromatic interactions present in Somatostatin. Replacement of each of the Phe residues (positions 6, 7 and 11) by Dfp and use of a D-Trp8 yielded peptides whose main conformations could be characterized in aqueous solution by NMR. Receptor binding studies revealed that the analog with Dfp at position 7 displayed a remarkable affinity to SSTR2 and SSTR3. Analogs with Dfp at positions 6 or 11 displayed a π-π interaction with the Phe present at 11 or 6, respectively. Interestingly, these analogs, particularly [D-Trp8,L-Dfp11]-SRIF, showed high selectivity towards SSTR2, with a higher value than that of Octreotide and a similar one to that of native Somatostatin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / chemistry
  • Amino Acid Sequence
  • Binding Sites
  • Halogenation
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Structure
  • Peptides, Cyclic / chemical synthesis*
  • Peptides, Cyclic / chemistry
  • Peptides, Cyclic / pharmacology*
  • Somatostatin / analogs & derivatives*
  • Somatostatin / chemistry
  • Structure-Activity Relationship

Substances

  • Peptides, Cyclic
  • Somatostatin
  • Alanine