Polymorphic structures triplexes

DNA is prone to structural polymorphism its sttucture can differ markedly from the classical donble hehx. For example, under snperhehcal stress, circnlar closed DNA can adopt an unnsnal structure, denoted H-DNA, in which homopurine-homopyrimidine tracts unwind and ntUize the pyrimidine-rich strand to form an intramolecnlar triplex with another homopnrine homopyrimidine tract the remaining purine single strand is left unpaired. The formation of H-DNA reqnires the presence of metal ions such as Mg + or... 

CP/MAS NMR of Scleroglucan. Solid, crystalline scleroglucan exists as a single anhydrous polymorph in contrast to the several crystalline forms of curdlan (8). Bluhm (8) proposed that the molecular conformation of scleroglucan is a triplex structure with a repeat distance along the chain... 

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