Year: 2022

HYBRID. “Part of the stimulus came from the development of the idea that DNA might not exist as a continuously coiled double helix but that it might adopt a side-by-side conformation.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

TECHNICAL LIMITATION. “In the face of suggestions of this type, it was clear that the fiber diffraction studies with their limited information content could no longer be responsive to the question of what detailed conformations DNA is capable of accommodating.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

PURE CRYSTALS. “The recent development of chemical methods for synthesizing DNA made it possible to produce oligonucleotides in amounts great enough for crystallization experiments.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

TECHNICAL RESOLUTION. “Unlike fiber diffraction patterns, single crystals can diffract to a very high resolution and they produce very large numbers of reflections or experimental measurements. This in turn makes it possible to solve the structures and observe fine details of DNA conformation in which very little or no interpretation is required.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

FIRST MILESTONE. “The first visualization of the double helix at atomic resolution occurred almost ten years ago with the solution of the structures of rApU and rGpC which were found to form right-handed double helical fragments of the type which had been anticipated for RNA molecules.” (1982). https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

STABILIZED CRYSTALS. “It was discovered that crystals could be formed readily using magnesium and spermine as cations. Furthermore, these crystals diffracted to 0.91 resolution.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

THE SURPRISE. “The resultant structure was quite unusual. It was a left-handed helix. However, it was not a simple left-handed helix, but one in which the alternating purine-pyrimidine sequence of the oligonucleotide was used in a unique way.” https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn

SO ENDS this first of two weekends on an historic paper on DNA chirality. There are some items that we take for granted, but on closer scrutiny, it was based on assumptions required because the methodology did not have sufficient precision. And so was the case with the assumed handedness of DNA. Other-handed DNA proved not only to exist but have relevance in disease. https://link.springer.com/content/pdf/10.1007/978-94-009-7052-6.pdf View in LinkedIn