title: Chimeric peptide of met-enkephalin and FMRFa: effect of chlorination on conformation and analgesia.
abstract: In our previous study YFa (YGGFMKKKFMRFa), a chimeric peptide of met-enkephalin and FMRFa, not only produced analgesia but also did not let the tolerance develop. In the continuation of the same study, Phe4 is chlorinated so as to assess the effect of chlorination on the conformation, lipophilicity and analgesia of chimeric peptide [p-Cl Phe(4)] YFa. Not only does the chlorination increase the lipophilicity but also enhances the propensity of [p-Cl Phe(4)] YFa to form alpha helix in comparison of YFa in presence of membrane mimicking solvent trifluoroethanol (TFE). This increase in lipophilicity and helix-forming ability results in more bioavailability and naloxone-reversible analgesia by [p-Cl Phe(4)] YFa. Though analgesia produced by [p-Cl Phe(4)] YFa is more than YFa at all doses, there is sudden decrease in analgesia at 45 and 60 min at 60 mg/kg. This sudden decrease of analgesia seems to be due to desensitization of opioid receptors.
authors.affiliation: Peptide Synthesis Laboratory, Institute of Genomics and Integrative Biology, Mall Road, Delhi 110007, India.
authors.forename: Kashif
authors.initials: K
authors.lastname: Hanif
authors.forename: Kshitij
authors.initials: K
authors.lastname: Gupta
authors.forename: Suparna
authors.initials: S
authors.lastname: Gupta
authors.forename: Y K
authors.initials: YK
authors.lastname: Gupta
authors.forename: Souvik
authors.initials: S
authors.lastname: Maiti
authors.forename: Santosh
authors.initials: S
authors.lastname: Pasha
mesh_terms: D000698:Analgesia; D000701:Analgesics, Opioid / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D002942:Circular Dichroism; D004744:Enkephalin, Methionine / Q000737:chemistry / Q000494:pharmacology* / Q000502:physiology; D019835:FMRFamide / Q000737:chemistry / Q000494:pharmacology* / Q000502:physiology; D008297:Male; D051379:Mice; D000442:Octanols; D009842:Oligopeptides / Q000737:chemistry / Q000494:pharmacology*; D010146:Pain / Q000378:metabolism / Q000503:physiopathology*; D017433:Protein Structure, Secondary; D012995:Solubility; D014867:Water
chemical_list: C513683:(p-Cl Phe(4))YFa; D000701:Analgesics, Opioid; D000442:Octanols; D009842:Oligopeptides; D014867:Water; D004744:Enkephalin, Methionine; D019835:FMRFamide