title: Synthesis and biological activities of YkFA analogues: effects of position 4 substitutions and altered ring size on in vitro opioid activity.
abstract: Substitution in position 4 of the potent opioid peptide YkFA with aliphatic hydrophobic residues resulted in compounds that retained low nanomolar activities at both mu and delta opioid receptors, while ring contraction by incorporation of diaminobutyric acid in position 2 resulted in a more pronounced decrease in potency at both receptors for the psi[CH(2)NH] pseudopeptide as compared to the all amide parent.
authors.affiliation: Department of Chemistry, University of Louisville, Louisville, KY 40292, USA.
authors.forename: John E
authors.initials: JE
authors.lastname: Burden
authors.forename: Peg
authors.initials: P
authors.lastname: Davis
authors.forename: Frank
authors.initials: F
authors.lastname: Porreca
authors.forename: Arno F
authors.initials: AF
authors.lastname: Spatola
mesh_terms: D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D013058:Mass Spectrometry; D010456:Peptides, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D010456:Peptides, Cyclic; C403249:tyrosyl-cyclo(lysyl-phenylalanyl-alanyl)