Molecular Structure of Deoxyribonucleic Acid (Dna)

Abstract

Although DNA is associated with complex biological phenomena and has many physicochemical properties not easily explained, there is no doubt that the molecule consists to a large extent of the regular, and in some ways simple structure (1-3), derived from x-ray diffraction. We will describe here briefly new data on the structure-the x-ray diffraction measurements and molecular model building being much more exact than in our previous publications (4, 5).The DNA molecule has internal flexibility which enables the helical structure in the solid state to be twisted into either of two well defined configurations or changed reversibly from one to the other, e.g. (6). Proof of the correctness of the structure is doubly convincing because DNA can be studied in these two different forms. This proof resides in the fact that, with a base pairing of the Watson and Crick type (7), the helical structure may be arranged in these two ways, each of which is in agreement with the corresponding diffraction data.We have already published some data on the B configuration (4) and discussed the nature of the A configuration (5). Here we give a preliminary account of more accurate data for both the B and A configuration. The procedure in this work is to build molecular models making use of interatomic bond lengths and angles obtained from measurements on relatively simple compounds and to calculate the x-ray diffraction intensities expected from such a structure. The model is then adjusted until the calculated diffraction corresponds with the measured x-ray intensities. The B Configuration of the DNA Molecule:When bound to protein in cells, DNA molecules exist in the B configuration (4).

The Molecular Basis of Heredity

“…The sugar-phosphate chains were regarded as held together by pairs of hydrogen bonds, between a purine base attached to one chain and a pyrimidine base attached to the other, the flat rings of these bases lying approximately perpendicular to the main axis of the helices (VIII). The main features of this structure, at first somewhat hypothetical, have now been proved by careful and elegant X-ray studies of not only the sodium salt but also those of other alkali metals (Feughelman et al 1955;Langridge et al 1957Langridge et al , 1960aWilkins, 1956a, b).…”

IDDRRA: A novel platform, based on Geant4‐DNA to quantify DNA damage by ionizing radiation

“…Each DNA base pair weighs 650 Daltons (g/mol). [62][63][64] Moreover, it is known that the following mathematical functions apply:…”

Evidence for the implication of the histone code in building the genome structure

“…Histones were first identified as a fundamental component of the nucleus in the early days of molecular biology [26,27] and were described as circular structures responsible for compacting DNA [1,6,28]. They were soon associated with DNA periodicity and compaction [6,[29][30][31][32], where DNA coils around an octamer of four core histone proteins (H2A/H2B dimer and H3/H4 tetramer, Figure 2A) [1,33]. The histone core with DNA was termed nucleosome and is known to be the first level of chromatin compaction.…”