Key Structural Features of Nucleic Acids

The critical featine of DNA is its linear order of the four nucleotides. The structure of DNA physically protects the all-important atoms of the bases from chemical modification by enviromnent. In cells, DNA occins predominantly in antiparallel double stranded forms plus-strand in 5 — 3 and minus strand in 3 5 directions. The two strands are heli- 

The sugars and phosphate are located toward one side of the A—T and G—C base pairs. In a typical DNA duplex, the phosphodiester backbones are on the outside of the structme, while the bps are internal. The spaces between the two backbones are called 

There are two preferred orientation anti and syn) of the base with respect to the sugar, as determined by steric restrictions during the torsion (%) about the CT—N glyco-syl bond. The sugar is nonplanar, and two of its common puckering modes are C2 -endo (S-type) and C3 -endo (A-type). The secondary stracture of DNA can be described by a number of parameters that define the helix (Dickerson et al 1989)  

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RESTRAINED REFINEMENT OF THE MONOCLINIC FORM OF YEAST PHENYLALANINE TRANSFER RNA. TEMPERATURE FACTORS AND DYNAMICS, COORDINATED WATERS, AND BASE-PAIR PRORELLER TWIST ANGLES 

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