title: A potentiometric and spectroscopic study of the proton and copper(II) complexes of methionine enkephalin and some related ligands.
abstract: The results are reported of a potentiometric and spectrophotometric study of the proton and copper(II) complexes of methionine enkephalin and four related pentapeptides which all show greater biological activity than their parent enkephalin. Measurements were carried out at 25 degrees C and I = 0.10 mol dm-3 (KNO3). All the ligands studied form stable copper(II) complexes comparable to those formed by pentaglycine, with the peptide chain locked in a folded conformation by NNN or NNNN coordination to the metal ion. There is no indication of bonding through the tyrosine-phenolate oxygen atoms or the methionine sulfurs.
mesh_terms: D003300:Copper / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D009842:Oligopeptides / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D008024:Ligands; D009842:Oligopeptides; D004744:Enkephalin, Methionine; D003300:Copper