Science is about making connections. Plenty are on show in Watson and Crick’s famous 1953 article on the structure of DNA[cite]10.1038/171737a0[/cite] but often with the tersest of explanations. Take for example their statement “ Both chains follow right-handed helices “. Where did that come from?
AbstractThe topological analysis of chiral molecular models has provided the framework of a general system for the specification of their chirality. The application, made in and before 1956, of this system to organic‐chemical configurations is generally retained, but is redefined with respect to certain types of structure, largely in the light of experience gained since 1956 in the Beilstein Institute and elsewhere. The system is now extended to deal, on the one hand, with organic‐chemical conformations, and, on the other, with inorganic‐chemical configurations to ligancy six. Matters arising in connexion with the transference of chiral specifications from model to name are considered, notably that of the symbiosis in nomenclature of expressions of the general system and of systems of confined scope.For corrigendum see DOI:10.1002/anie.196605111
AbstractThe usefulness of modern density functional theory (DFT) methods is considered for establishing the absolute configurations of DNA lesions by comparisons of computed and experimentally measured optical rotatory dispersion (ORD) and electronic circular dichroism (ECD) spectra. Two rigid, structurally different DNA lesions (two spiroiminodihydantoin stereoisomers and four equine estrogen 4‐hydoxyequilenin—DNA stereoisomeric adducts) have been investigated. In all cases, the signs and shapes of the computed ORD spectra reproduced the experimentally measured ORD spectra, although the magnitudes of the computed and experimental ORD values do not coincide exactly. The computed ECD spectra also reproduced the shapes of the experimental ECD spectra rather well, but are blue‐shifted by 10–20 nm. Since the assignments of the absolute configurations of the DNA lesions studied based on computed and experimental ORD and ECD spectra are fully consistent with one another, the computational DFT method shows significant promise for determining the absolute configurations of DNA lesions. Establishing the stereochemistry of DNA lesions is highly useful for understanding their biological impact, especially when sufficient amounts of material are not available for other methods of structural characterization. Chirality 21:E231–E241, 2009. © 2009 Wiley‐Liss, Inc.
This paper describes a possible structure for the paracrystalline form of the sodium salt of deoxyribonucleic acid. The structure consists of two DNA chains wound helically round a common axis, and held together by hydrogen bonds between specific pairs of bases. The assumptions made in deriving the structure are described, and co-ordinates are given for the principal atoms. The structure of the crystalline form is discussed briefly.