title: Nociceptin and its natural and specifically-modified fragments: Structural studies.
abstract: The vibrational structures of Nociceptin (FQ), its short bioactive fragments, and specifically-modified [Tyr¹]FQ (1-6), [His¹]FQ (1-6), and [His(1,4)]FQ (1-6) fragments were characterized. We showed that in the solid state, all of the aforementioned peptides except FQ adopt mainly turn and disordered secondary structures with a small contribution from an antiparallel β-sheet conformation. FQ (1-11), FQ (7-17) [His¹]FQ (1-6), and [His(1,4)]FQ (1-6) have an α-helical backbone arrangement that could also slightly influence their secondary structure. The adsorption behavior of these peptides on a colloidal silver surface in an aqueous solution (pH = ∼8.3) was investigated by means of surface-enhanced Raman scattering (SERS). All of the peptides, excluding FQ (7-17), chemisorbed on the colloidal silver surfaces through a Phe⁴ residue, which for FQ, FQ (1-11), FQ (1-6), [Tyr¹]FQ (1-6), and [His¹]FQ (1-6) lies almost flat on this surface, while for FQ (1-13) and FQ (1-13)NH₂ adopts a slightly tilted orientation with respect to the surface. The Tyr¹ residue in [Tyr¹]FQ (1-6) does not interact with the colloidal silver surface, suggesting that the Tyr¹ and Phe⁴ side chains are located on the opposite sides of the peptide backbone, which can be also true for His¹ and Phe⁴ in [His¹]FQ (1-6). The lone pair of electrons on the oxygen atom of the ionized carbonyl group of FQ (1-13) and FQ (7-17) appears to be coordinated to the colloidal silver nanoparticles, whereas in the case of the remaining peptides, it only assists in the adsorption process, similar to the --NH⁴ group. We also showed that upon adsorption, the secondary structure of these peptides is altered.
authors.affiliation: Faculty of Chemistry, Jagiellonian University, 30-060 Krakow, Poland.
authors.forename: E
authors.initials: E
authors.lastname: Podstawka-Proniewicz
authors.forename: M
authors.initials: M
authors.lastname: Kosior
authors.forename: Y
authors.initials: Y
authors.lastname: Kim
authors.forename: K
authors.initials: K
authors.lastname: Rolka
authors.forename: L M
authors.initials: LM
authors.lastname: Proniewicz
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D008969:Molecular Sequence Data; D018847:Opioid Peptides / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry*; D010649:Phenylalanine / Q000737:chemistry; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014443:Tyrosine / Q000737:chemistry; D000097629:Nociceptin
chemical_list: D000596:Amino Acids; D006639:Histidine; D018847:Opioid Peptides; D010446:Peptide Fragments; D010649:Phenylalanine; D014443:Tyrosine; D000097629:Nociceptin