title: Noncovalent interactions of peptides with porphyrins in aqueous solution: conformational study using vibrational CD spectroscopy.
abstract: Noncovalent interactions of poly(L-lysine) (PL), oligopeptides L-lysyl-L-alanyl-L-alanine and (L-lysyl-L-alanyl-L-alanine)(2) with meso-tetrakis(4-sulfonatophenyl)porphine (TPPS), and poly(L-glutamic acid) (PLGA) with meso-tetrakis(1-methyl-4-pyridyl)porphine tetra-p-tosylate (TMPyP) in aqueous solutions have been studied using combination of spectroscopic methods: Vibrational circular dichroism (VCD) spectroscopy in the mid-infrared region provides a direct information on conformational changes of the polypeptides and oligopeptides caused by interactions with porphyrins; ultraviolet-visible absorption, fluorescence, and electronic circular dichroism (ECD) reveal the aggregation characterization of the porphyrin part of the complexes. Interactions of TPPS with tripeptide, hexapeptide, and PL containing about ten amino acid residues in the molecular chain are accompanied with the changes of VCD patterns in the amide I' region. In these cases, the conformation of the oligopeptide part of complexes is obviously influenced by interactions with TPPS and partial changes of random coil structure are observed in VCD. When PL was composed of the hundreds of lysine residues, just a weak intensity decrease was detected and the shape of VCD spectrum typical for the random coil structure was preserved. As follows from the uv-vis absorption and fluorescence spectra, porphyrin molecules are attached to peptides by electrostatic interaction as a monomer or dimer and interaction between porphyrin and peptide depends on the polypeptide chain length. For the PLGA-TMPyP system with PLGA containing from tens to hundreds of glutamic acid residues in the chain, the VCD spectra were unchanged when TMPyP was presented in the aqueous solution of PLGA and random coil conformation of PLGA-TMPyP aggregates was preserved.
authors.affiliation: Department of Physics and Measurements, Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic. marie.urbanova@vscht.cz
authors.forename: M
authors.initials: M
authors.lastname: Urbanová
authors.forename: V
authors.initials: V
authors.lastname: Setnicka
authors.forename: V
authors.initials: V
authors.lastname: Král
authors.forename: K
authors.initials: K
authors.lastname: Volka
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002942:Circular Dichroism; D004791:Enzyme Inhibitors / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000737:chemistry; D008956:Models, Chemical; D010455:Peptides / Q000737:chemistry*; D017319:Photosensitizing Agents / Q000737:chemistry; D011100:Polyglycolic Acid / Q000737:chemistry; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D011838:Radiation-Sensitizing Agents / Q000737:chemistry; D013053:Spectrophotometry; D014867:Water
chemical_list: D001672:Biocompatible Materials; D004791:Enzyme Inhibitors; D010455:Peptides; D017319:Photosensitizing Agents; D011108:Polymers; D011166:Porphyrins; D011838:Radiation-Sensitizing Agents; D014867:Water; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C016136:tetraphenylporphine sulfonate; C021096:tetra(4-N-methylpyridyl)porphine