Blue copper proteins tetragonal structure

Having summarized the types of transitions which are likely to contribute to the absorption spectrum of tetragonal copper (II), it is important to consider methods which probe these transitions and maximize the amount of information which can be ascertained. Linear dichroism13) provides the specific orientation of the electric dipole transition moment (Eq. 3) with respect to the copper site. This method is quite valuable in assigning an absorption spectrum (as discussed for Blue Copper proteins in Sect. Ill) but requires a structurally defined site oriented in a single crystal. A number of other physical... 

Why does a Cu(II) ion with the ligands in the blue copper proteins assume a trigonal structure, whereas most inorganic cupric conplexes are tetragonal (square planar, square pyramidal, or distorted octahedral) [63,64] We have faced this question by optimising the geometry of a number of models of the type... 

Another problem with small models is that molecules from the solution (e.g. water) may come in and stabilise tetragonal structures and higher coordination numbers [224]. It is illustrative that very few inorganic con5)lexes reproduce the properties of the blue copper proteins [66,67], whereas typical blue-copper sites have been constructed in several proteins and peptides by metal substitution, e.g. insulin, alcohol dehydrogenase, and superoxide dismutase [66]. This shows that the problem is more related to protection from water and dimer formation than to strain. 

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