page_title: Hemocyanin
section_title: Spectral properties
hierarchical_section_title: Hemocyanin / Spectral properties
caption_attribution_description: English: deoxy form of the hemocyanin active site
context_page_description: Hemocyanins are proteins that transport oxygen throughout the bodies of some invertebrate animals. These metalloproteins contain two copper atoms that reversibly bind a single oxygen molecule. They are second only to hemoglobin in frequency of use as an oxygen transport molecule. Unlike the hemoglobin in red blood cells found in vertebrates, hemocyanins are not bound to blood cells but are instead suspended directly in the hemolymph. Oxygenation causes a color change between the colorless Cu(I) deoxygenated form and the blue Cu(II) oxygenated form.
context_section_description: Spectroscopy of oxyhemocyanin shows several salient features:
  Resonance Raman spectroscopy shows that O2 is bound in a symmetric environment (ν(O-O) is not IR-allowed).
  OxyHc is EPR-silent indicating the absence of unpaired electrons
  Infrared spectroscopy shows ν(O-O) of 755 cm⁻¹
  Much work has been devoted to preparing synthetic analogues of the active site of hemocyanin. One such model, which features a pair of copper centers bridged side-on by peroxo ligand, shows ν(O-O) at 741 cm⁻¹ and a UV-Vis spectrum with absorbances at 349 and 551 nm.  Both of these measurements agree with the experimental observations for oxyHc. 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).
caption: A hemocyanin active site in the absence of O2 (each Cu center is a cation, charges not shown).
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