Nucleic Acids in Chemistry and Biology

monoesters on the same sugar are called nucleoside bisphosphateswhereas nucleoside monoesters of
pyrophosphoric acid are nucleoside diphosphates. By extension, nucleoside esters of tripolyphosphoric
acid are nucleoside triphosphatesof which the classic example is adenosine 5
-triphosphate (ATP)
(Section 3.3.2). Finally, cyclic nucleotides are nucleosides which have two neighbouring hydroxyl groups
on the same pentose esterified by a single phosphate as a diester. The most important of these is adenosine
3
,5
-cyclic phosphate (cAMP).

DNA and RNA Structure 15

O

HO OH

N

N

N

N

O NH 2

P

O

O

O

2Na

O

OH

N

NH

N

N

O O

P

O

O

O

NH 2

OP O

O O

4Na

2Na

O

N

N

NH 2

HO

O

O O

P

O O

Na

O

N

NH

O

HO

O

O

O

P

O

O

Adenosine 5'-monophosphate 3'-monophosphateDeoxycytidine

Guanosine

3',5'-bisphosphate

Uridine

2',3'-cyclicphosphate

Figure 2.4 Structures of some common nucleotides. All are presented as their sodium salts in the state of

ionization observed at neutral pH

Figure 2.3 Structures of the four major deoxyribonucleosides. By convention, only hydrogens bonded to oxygen or
nitrogen are depicted

Figure 2.2 Structures of the four ribonucleosides. The bases retain the same numbering system and the pentose car-
bons are numbered 1
through 5
. By convention, the furanose ring is drawn with its ring oxygen at the
back and C-2
and C-3
at the front. Hydrogen atoms are usually omitted for clarity