Tetragonal typical properties

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. 

This material characteristic is referred to as "phase transformation toughening" (Cales 2000). However, the phase-induced volumetric transformation can also have disastrous consequences if not properly controlled. For this reason, the phase transformation property of zirconia is typically stabilized with the addition of magnesia or yttria (Willmann 1998). The most common type of zirconia used in orthopedics is termed Y-TZP, corresponding to yttria stabilized-tetragonal phase, polycrystalline zirconia (Willmann 1998). The chemical composition of Y-TZP is approximately 5.1% yttria (Y2O3) and 93-94% zirconia (Zr02) (Cales 2000). 

Copper sites in proteins have traditionally been classified into three classes blue type 1 sites (present in the blue copper proteins), normal type 2 sites (tetragonal mononuclear copper sites), and type 3 (spin-coupled pairs of copper ions). The type 1 sites have been further classified as axial or rhombic depending on their EPR (and other spectroscopic) characteristics." Plastocyanin (axial) and nitrite reductase (rhombic) are typical examples of type 1 proteins. Proteins with properties intermediate between those of type 1 and type 2 sites have been termed type 1.5." ... 

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