Sugar phosphates structure

Ultrasonic relaxation techniques have been used to estimate the energy barrier to syn-anti conformational interconversion in cytidine 2, 3 -mono-phosphate, in the presence and absence of ethidium bromide. Raman spectroscopic measurements on a number of dinucleoside monophosphate crystals of precisely known sugar-phosphate structure have been compared with those of B- and A-form DNA, to give information on the comparative rigidity of the backbone in the nucleic acids. The same technique, applied to poly(dA-dT) and poly[d(A-T)] at different temperatures, suggests that some of the furanose... 

Protons bound to heteroatoms in heterocyclic compounds are likely to be very mobile in solution and, where two or more heteroatoms are present in a structure, different isomers (tautomers) may be in equilibrium. As a case in point, consider the nucleotide bases (indicates the point of attachment to the sugar-phosphate backbone). 

DNA is made up ot two intertwined strands. A sugar-phosphate chain makes up the backbone of each, and the two strands are joined by way of hydrogen bonds betwen parrs of nucleotide bases, adenine, thymine, guanine and cytosine. Adenine may only pair with thymine and guanine with cytosine. The molecule adopts a helical structure (actually, a double helical stnrcture or double helix ). 

The structure of DNA. (a) A ball-and-stick model, with the sugar-phosphate backbone colored blue and the bases colored red. b) A space-filling model, showing C atoms in blue, N atoms in dark blue, H atoms in white, O atoms in red, and P atoms in yellow. 

The structures of DNA and RNA are similar in that each has a sugar-phosphate backbone with one organic base bound to each sugar. However, there are four distinct differences between RNA and DNA ... 

Fig. 1 The w-stack of double helical DNA. In this idealized model of B-DNA the stack of heterocyclic aromatic base pairs is distinctly visible within the sugar-phosphate backbone (schematized by ribbons) a view perpendicular to the helical axis b view down the helical axis. It is the stacking of aromatic DNA bases, approximately 3.4 A apart, that imparts the DNA with its unique ability to mediate charge transport. Base stacking interactions, and DNA charge transport, are exquisitely sensitive to the sequence-depen-dent structure and flexibility of DNA...

In forming the double-helix polymeric DNA structure, the two sugar-phosphate backbones twist around the central stack of base pairs, generating a major and minor groove. Several conformations, known as DNA polymorphs, are possible. 

Figure 4.16 The structure of yeast tRNAplle (a) the cloverleaf form of the base sequence tertiary base-pairing interactions are represented by thin red lines connecting the participating bases. Bases that are conserved in all tRNAs are circled by solid and dashed lines, respectively. The different parts of the structure are colour-coded, (b) The X-ray structure showing how the different base-paired stems are arranged to form an L-shaped molecule. The sugar-phosphate backbone is represented as a ribbon with the same colour scheme as in (a). (From Voet and Voet, 2004. Reproduced with permission from John Wiley Sons., Inc.)...

Figure 13.4 Oligonucleotide structure. The nucleotides are joined via the phospho-diester bridges between sugar residues. The bases stick out away from the sugar-phosphate backbone.

Watson and Crick showed that the normal structure of DNA consists of a double helix made from two single oligonucleotide strands. The two sugar-phosphate strands of the helix run in opposite (anti-parallel) directions and the bases point... 

The torsion angles around the bonds of the sugar-phosphate DNA backbone are of decisive importance for the secondary structure of DNA as well as for base-base recognition. [44] For antisense agents to be effective inhibitors of protein expression in vivo, they have to resist the action of DNA-degrading enzymes and bind to their... 

Figure 12.3 The double hehx of DNA. The sugar-phosphate backbones wind about the periphery of the molecule in opposite directions. The hydrogen-bonded base pairs occupy the core of the structure and are basically flat and lie perpendicular to the long axis of the helix. (Illustration, Irving Geis/Geis Archives Trust. Howard Hughes Medical Institute. Reproduced with permission.)...

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