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Triple-stranded DNA (also known as H-DNA or Triplex-DNA) is a DNA structure in which three oligonucleotides wind around each other and form a triple helix. In triple-stranded DNA, the third strand binds to a B-form DNA (via Watson–Crick base-pairing ) double helix by forming Hoogsteen base pairs or reversed Hoogsteen hydrogen bonds.
A DNA triple helix is made up of three separate DNA strands, each oriented with the sugar/phosphate backbone on the outside of the helix and the bases on the inside of the helix. The bases are the part of the molecule closest to the triple helix's axis, and the backbone is the part of the molecule farthest away from the axis.
In a triple-helix model (specifically Pauling and Corey's model), some of the van der Waals distances appear to be too small. The initial double helix model discovered, now termed B-form DNA is by far the most common conformation in cells. [12]
In early 1953, Pauling published a triple helix model of DNA, which subsequently turned out to be incorrect. [3] Both Crick, and particularly Watson, thought that they were racing against Pauling to discover the structure of DNA. Max Delbrück was a physicist who recognized some of the biological implications of quantum physics.
The DNA double helix structure proposed by Watson and Crick was based upon "Watson-Crick" bonds between the four bases most frequently found in DNA (A, C, T, G) and RNA (A, C, U, G). However, later research showed that triple-stranded, quadruple-stranded and other more complex DNA molecular structures required Hoogsteen base pairing.
Pauling then proposed that deoxyribonucleic acid (DNA) was a triple helix; [60] [61] his model contained several basic mistakes, including a proposal of neutral phosphate groups, an idea that conflicted with the acidity of DNA. Sir Lawrence Bragg had been disappointed that Pauling had won the race to find the alpha helix structure of proteins ...
One long-standing theory is that the disease emerged in the Americas and migrated to Europe after the expeditions led by Christopher Columbus returned from the New World, but a new study suggests ...
The tertiary arrangement of DNA's double helix in space includes B-DNA, A-DNA, and Z-DNA. Triple-stranded DNA structures have been demonstrated in repetitive polypurine:polypyrimidine Microsatellite sequences and Satellite DNA. B-DNA is the most common form of DNA in vivo and is a more narrow, elongated helix than A-DNA. Its wide major groove ...