title: Salt-dependent conformational diversity of alternating poly (Glu-Leu).
abstract: Alternating poly(Glu-Leu) was synthesized by the condensation of the corresponding dipeptide p-nitrophenyl ester at high concentration. It exhibits a random coil structure in pure water at neutral pH. Addition of monovalent cations, such as NH4+ to a final 0.1 M solution, induces a transition to a water soluble beta-structure. The salt effect is quite selective since no transition was observed with Li+, Na+ or Cs+ ions. Addition of 0.5 equiv of calcium, cobalt or manganese chlorides per glutamyl residue induces similar coil to beta-sheet transitions. No polymer precipitation was observed at these very low salt concentrations. Addition of 0.5 equiv. of Cu2+ or 0.15 equiv. of Fe3- induces a coil to alpha-helix transition. Molecular modeling has been used to understand tentatively the main factors controlling the different conformations observed with the various metal ions.
authors.affiliation: Molecular Biophysics Centre, CNRS, Orléans, France.
authors.forename: M
authors.initials: M
authors.lastname: Bertrand
authors.forename: D
authors.initials: D
authors.lastname: Sy
authors.forename: A
authors.initials: A
authors.lastname: Brack
mesh_terms: D000641:Ammonia / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002942:Circular Dichroism; D003300:Copper / Q000494:pharmacology; D004151:Dipeptides / Q000737:chemistry; D018698:Glutamic Acid / Q000737:chemistry*; D007501:Iron / Q000494:pharmacology; D007930:Leucine / Q000031:analogs & derivatives* / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry*; D011099:Polyglutamic Acid / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012492:Salts / Q000494:pharmacology; D012995:Solubility
chemical_list: D004151:Dipeptides; D009842:Oligopeptides; D012492:Salts; C106782:poly(glutamic acid-leucine); D011099:Polyglutamic Acid; D018698:Glutamic Acid; D000641:Ammonia; D003300:Copper; D007501:Iron; D007930:Leucine; D002118:Calcium