Year: 2022

THE PROBLEM. “The X-ray diffraction patterns were limited, and far from atomic resolution. Because of the limited resolution the patterns had to be interpreted and a number of assumptions made.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

THE MANTRA. “One assumption was that the structure was perfectly regular with an asymmetric unit consisting of one nucleotide. However, the agreement was reasonable and this led to the general adoption of the right-handed B-DNA conformation as the predominant form in biological systems.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

METHODOLOGICAL LIMITATIONS. “Considerable attention was paid to the fact that under certain conditions alternative conformational variants were seen. The most important of these was the A-DNA pattern which originally was produced by air-dried fibers.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

THE VARIANTS. “The greater wealth of diffraction data seen in the A pattern made it possible to get more information. The relative ease with which it slipped into the B pattern reinforced the idea that these were two conformational variants; it was found that both patterns could be fitted by a right-handed double helix.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

LEVOROTATORY VARIANT. “Although there was discussion of the possibility of left-handed helices, especially shortly after the double helix formulation, there were very few systematic studies of left-handed helices published during the next decade or so.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

HYPOTHETICAL FUNCTION. “Left-handed double helical DNA regions might be anticipated to facilitate replication fork movement and chain separation during DNA replication.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

ELEPHANT IN THE ROOM. “Helical flexibility as a mechanism to either generate structural recognition signals along the DNA molecule or regulate superhelical topology was not discussed extensively.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

ALTERNATIVE FORMS. “It is only relatively recently that there has been increased emphasis on alternative conformational models for DNA.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn