title: Aqueous gel formation of a synthetic peptide derived from the beta-sheet domain of platelet factor-4.
abstract: We observed gelation of a 23-residue peptide derived from the beta-sheet domain of platelet factor-4 (PF4(24)(-)(46)). The gels were primarily heterogeneous mixtures of 50-200 microm spherical aggregates in a less-dense gel matrix. Infrared and circular dichroism spectroscopies showed gelation involving the conversion of PF4(24)(-)(46) from random coil to beta-sheet. We used aggregation-induced NMR resonance broadening to show that temperature, pH, and ionic strength influenced PF4(24)(-)(46) gelation rates. Under identical solution conditions, gel formation took days at T </= 20 degrees C but only 30 min at T >/= 50 degrees C. Gelation was most rapid at pH values near the pK(a) of the central His35 residue. Increases in solution ionic strength reduced the critical gelation concentration of PF4(24)(-)(46). Our results suggest that PF4(24)(-)(46) gels by a process combining aspects of both heat-set and beta-fibril gelation mechanisms.
authors.affiliation: Department of Biochemistry, Molecular Biology & Biophysics, the Biomedical Engineering Center, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Lockwood
authors.forename: Robert
authors.initials: R
authors.lastname: van Tankeren
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Mayo
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D005782:Gels / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D010446:Peptide Fragments / Q000737:chemistry*; D010978:Platelet Factor 4 / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013057:Spectrum Analysis; D013696:Temperature; D014867:Water
chemical_list: D001672:Biocompatible Materials; D005782:Gels; D010446:Peptide Fragments; D014867:Water; D010978:Platelet Factor 4