Editing Hemocyanin (section)

== Spectral properties ==

[[File:Hemocyanin Example.jpg|thumb|The underside of the '''carapace''' of a red rock crab (''[[Cancer productus]]''). The purple coloring is caused by hemocyanin.]]
Spectroscopy of oxyhemocyanin shows several salient features:<ref name=Tolman/>
# Resonance [[Raman spectroscopy]] shows that {{chem|O|2}} is bound in a symmetric environment (ν(O-O) is not IR-allowed).
# OxyHc is [[electron paramagnetic resonance|EPR]]-silent indicating the absence of unpaired electrons
# [[Infrared spectroscopy]] shows ν(O-O) of 755&nbsp;cm<sup>−1</sup>

Much work has been devoted to preparing synthetic analogues of the active site of hemocyanin.<ref name="Tolman">{{cite journal | vauthors = Elwell CE, Gagnon NL, Neisen BD, Dhar D, Spaeth AD, Yee GM, Tolman WB | title = Copper-Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity | journal = Chemical Reviews | volume = 117 | issue = 3 | pages = 2059–2107 | date = February 2017 | pmid = 28103018 | pmc = 5963733 | doi = 10.1021/acs.chemrev.6b00636 }}</ref> One such model, which features a pair of copper centers bridged side-on by peroxo ligand, shows ν(O-O) at 741&nbsp;cm<sup>−1</sup> and a UV-Vis spectrum with absorbances at 349 and 551&nbsp;nm.  Both of these measurements agree with the experimental observations for oxyHc.<ref name="Kitajima">{{cite journal|display-authors=6|vauthors=Kitajima N, Fujisawa K, Fujimoto C, Morooka Y, Hashimoto S, Kitagawa T, Toriumi K, Tatsumi K, Nakamura A|date=1992|title=A new model for dioxygen binding in hemocyanin. Synthesis, characterization, and molecular structure of the μ-η2:η2 peroxo dinuclear copper(II) complexes, [Cu(BH(3,5-R2pz)3)]2(O2) (R = i-Pr and Ph)|journal=Journal of the American Chemical Society|volume=114|issue=4|pages=1277–91|doi=10.1021/ja00030a025}}</ref> The Cu-Cu separation in the model complex is 3.56 Å, that of oxyhemocyanin is ca. 3.6 Å (deoxyHc: ca. 4.6 Å).<ref name=Kitajima/><ref>{{cite journal | vauthors = Gaykema WP, Hol WG, Vereijken JM, Soeter NM, Bak HJ, Beintema JJ |title=3.2 Å structure of the copper-containing, oxygen-carrying protein Panulirus interruptus haemocyanin |journal=Nature |volume=309 |issue=5963 |pages=23–9 |year=1984 |doi=10.1038/309023a0 |bibcode=1984Natur.309...23G |s2cid=4260701 }}</ref><ref>{{cite journal|display-authors=6|vauthors=Kodera M, Katayama K, Tachi Y, Kano K, Hirota S, Fujinami S, Suzuki M|date=1999|title=Crystal Structure and Reversible O2-Binding of a Room Temperature Stable μ-η2:η2-Peroxodicopper(II) Complex of a Sterically Hindered Hexapyridine Dinucleating Ligand|journal=Journal of the American Chemical Society|volume=121|issue=47|pages=11006–7|doi=10.1021/ja992295q}}</ref>