Phosphates order-disorder

Lumpkin G. R. and Ribbe P. H. (1983). Composition, order-disorder and lattice parameters of olivines Relationships in silicate, germanate, beryllate, phosphate and borate olivine. Amer. Mineral, 68 164-176. 

Dihydrogen phosphate (KDP) - KH2PO4. It belongs to the ferroelectric species 42ffz mml with low Curie temperature -150°C. It is model material for ferroelectric order-disorder type of phase transition. Crystal was previously used... 

The DNA solvation shell consists of about 20-22 water molecules per nucleotide of these, — 15-17 waters associate with the nucleoside and —5 waters associate with the phosphate group [13,14]. Water outside the solvation layer is termed bulk water. Upon freezing, the DNA solvation water forms two primary phases the ice phase, consisting of one or more of the crystalline forms of ice, and a DNA-associated phase, consisting of ordered water which comes in direct contact with the DNA (primary layer) and disordered water in the secondary layer. DNA hydration is expressed in terms of F, the number of water molecules per nucleotide. 

Figure 6-5. Electrochemical potential controlled reversible domain formation of a singlestrand repetitive 10-adenine sequence linked to a single-crystal Au(lll)-electrode surface in aqueous phosphate buffer, pH 7.6. Left Domain formation after keeping the potential at -0.61 V (vs. saturated calomel electrode, SCE) for 40 min. Recording at -0.21 V (SCE). Middle Disorder after potential stepping to -0.05 V (SCE). Right Recovery of ordered domains from the disordered surface structure shown in the middle figure, after stepping the potential back to -0.61 V (SCE) and recording at -0.21 V (SCE). Reprinted from ref. 6 with permission.

Disorder-to-order transition covering active site (triose phosphate isomerase, penicil-lopepsin)... 

Another type of disorder-to-order transition is the so-called loop-cap transition in certain enzymes.279,280 This structural change is associated with a highly mobile loop of residues, from 6 to 12 amino acid residues in length, that are located near the active site. Such a structural feature has been identified in the enzyme triose phosphate isomerase (TIM). TIM makes an especially interesting case study for theoretical analysis of the loop-cap transition because there exist X-ray,279,313 kinetic,121 and thermodynamic data121 for this enzyme. 

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