Nucleic acid knots

Seeman, N.C. (1992) The design of single-stranded nucleic acid knots. Mol. Eng. 2, 297-307. 

Careful design was used by Seeman to prepare complementary DNA strands that self assemble into a cube with 20 nucleotide pairs along each edge. Other derivatives include nylon DNA , through the synthesis of peptide nucleic acids (PNA), and polyethylene glycol derivatized DNA. Figure 8.1 illustrates the DNA knots that can be prepared using these techniques. 

Xayaphoummine, A., Bucher, T and Isambert, H. (2005) Kinefold web server for RNA/DNA folding path and structure prediction including pseudoknots and knots, Nucleic Acid Res. 33, 605-610. 

All these chiral structural standards and the corresponding families around them in proteins and nucleic acids represent, however, only the main building blocks upon which evolution has been operating. The colored loop- and knot-stretches and all the more disordered parts of protein and nucleic acid structural designs are of primary importance for the evolutionary aspects of informational and functional processings in our evolving life patterns. 

Topoisomerases are enzymes that alter the topological state (e.g., over- and underwihding, knotting, or tangling) of nucleic acids by generating transient breaks... 

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