title: Interactions of disulfide-constrained cyclic tetrapeptides with Cu(2+).
abstract: The purpose of this work is to characterize the interactions of two disulfide-constrained cyclic tetrapeptides [c(Ac-Cys-Pro-Phe-Cys-NH(2)), SS1; c(Ac-Cys-Pro-Gly-Cys-NH(2)), SS2] with Cu(2+) ions in order to facilitate the design of cyclic peptides as sensors for metal ions. The Cu(2+)-peptide complex cations at m/z 569.1315 for Cu(2+)-SS1 and m/z 479.0815 for Cu(2+)-SS2 were detected by mass spectrometry. The gas-phase fragmentation of the Cu(2+)-peptide complexes was studied by collision-induced dissociation and suggests the atoms involved in the coordination. Cu(2+) ion binds to a single SS1 or SS2 with K (d(app)) of 0.57 ± 0.02 and 0.55 ± 0.01 μM, respectively. Isothermal titration calorimetry data indicate both enthalpic and entropic contributions for the binding of Cu(2+) ion to SS1 and SS2. The characteristic wavenumber of 947 cm(-1) and the changes at 1,664 and 1,530 cm(-1) in the infrared spectrum suggest that the sulfydryl of cysteine, the carbonyl group, and amide II are involved in the coordination of Cu(2+). The X-ray absorption near-edge structure signal from the Cu(2+)-peptide complex corresponds to the four-coordination structure. The extended X-ray absorption fine structure and electron paramagnetic resonance results demonstrate the Cu(2+) ion is in an S/N/2O coordination environment, and is a distinct type II copper center. Theoretical calculations further demonstrate that Cu(2+) ion binds to SS1 or SS2 in a slightly distorted tetragonal geometry with an S/N/2O environment and the minimum potential energy.
authors: Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, People's Republic of China. zly0605@ustc.edu.cn.|National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, People's Republic of China. zly0605@ustc.edu.cn.
authors: Liyun
authors: L
authors: Zhang
authors: School of life Sciences, University of Science and Technology of China, Hefei, Anhui, 230027, People's Republic of China.
authors: Zhaofeng
authors: Z
authors: Luo
authors: National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, People's Republic of China.
authors: Lidong
authors: L
authors: Zhang
authors: National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, People's Republic of China.
authors: Liangyuan
authors: L
authors: Jia
authors: Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, People's Republic of China.|School of life Sciences, University of Science and Technology of China, Hefei, Anhui, 230027, People's Republic of China.
authors: Lifang
authors: L
authors: Wu
mesh_terms: D000595:Amino Acid Sequence; D002151:Calorimetry; D002614:Chelating Agents / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D003553:Cystine / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D008970:Molecular Weight; D010456:Peptides, Cyclic / Q000737:chemistry*; D011485:Protein Binding; D017550:Spectroscopy, Fourier Transform Infrared; D056928:X-Ray Absorption Spectroscopy
chemical_list: D002614:Chelating Agents; D056831:Coordination Complexes; D010456:Peptides, Cyclic; C582336:cyclo(acetylcysteinyl-prolyl-glycyl-cysteinamide); C582335:cyclo(acetylcysteinyl-prolyl-phenylalanyl-cysteinamide); D003553:Cystine; D003300:Copper