Three conformal solution mixing

Three-Parameter, Corresponding-States Conformal Solution Mixing Rules for Mixtures... 

The isolation of crystalline products having mixed polymorphic compositions (often referred to as concomitant polymorphism) remains a topic of interest, even though the phase rule predicts that a system at equilibrium consisting two components (solvent + solute) and three phases (solution + Form I + Form II) is uni variant. Hence, for crystallizations performed at a fixed pressure (typically atmospheric) the system becomes nonvariant and genuine equilibrium can exist at only one temperature. Therefore, concomitant products must be obtained under nonequilibrium conditions. Flexibility in molecular conformation was attributed to the concomitant polymorphs of a spirobicyclic dione [34] and of 3-acetylcoumarin [35],... 

Several G-quadruplex structures have been reported. An intramolecular G-quadruplex from human telomeric DNA in the presence of potassium ions adopts a structure in which three strands run in one direction, the fourth strand in the opposite direction (3 + 1 topology). The structure of this qua-druplex has caused particular interest as it forms diflerent structures depending upon the counterion (Na or K ). Substitution of the guanine bases for 8-bromoguanine gives rise to two dilferent conformations of mixed-parallel/anti-parallel and a chair-t5q)e G-quadruplex. The G-quadruplex from the human Bcl-2 promoter region also forms a mixed parallel/antiparallel structure in solution. " " ... 

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