title: Developing predictive rules for coordination geometry from visible circular dichroism of copper(II) and nickel(II) ions in histidine and amide main-chain complexes.
abstract: Circular dichroism (CD) spectroscopy in the visible region (vis-CD) is a powerful technique to study metal-protein interactions. It can resolve individual d-d electronic transitions as separate bands and is particularly sensitive to the chiral environment of the transition metals. Modern quantum chemical methods enable CD spectra calculations from which, along with direct comparison with the experimental CD data, the conformations and the stereochemistry of the metal-protein complexes can be assigned. However, a clear understanding of the observed spectra and the molecular configuration is largely lacking. In this study, we compare the experimental and computed vis-CD spectra of Cu(2+)-loaded model peptides in square-planar complexes. We find that the spectra can readily discriminate the coordination pattern of Cu(2+) bound exclusively to main-chain amides from that involving both main-chain amides and a side-chain (i.e. histidine side-chain). Based on the results, we develop a set of empirical rules that relates the appearance of particular vis-CD spectral features to the conformation of the complex. These rules can be used to gain insight into coordination geometries of other Cu(2+)- or Ni(2+)-protein complexes.
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary, University of London, UK.
authors.forename: Helen F
authors.initials: HF
authors.lastname: Stanyon
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Cong
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.forename: Nabeela
authors.initials: N
authors.lastname: Shahidullah
authors.forename: Giulia
authors.initials: G
authors.lastname: Rossetti
authors.forename: Jens
authors.initials: J
authors.lastname: Dreyer
authors.forename: George
authors.initials: G
authors.lastname: Papamokos
authors.forename: Paolo
authors.initials: P
authors.lastname: Carloni
authors.forename: John H
authors.initials: JH
authors.lastname: Viles
mesh_terms: D000577:Amides / Q000737:chemistry*; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D011789:Quantum Theory
chemical_list: D000577:Amides; D009842:Oligopeptides; D006639:Histidine; D003300:Copper; D009532:Nickel
keywords: CD; Cu2+; Ni2+; density functional theory; protein