Biomedical Engineering Reference
In-Depth Information
Fig. 1.3
Nomenclature of a
four-base single strand of
DNA (GCAT). Molecules
representing the phosphate
group, having Na
C
as the
counter ion, and sugar units
are shown in the windows on
the left (top and bottom,
respectively)
O
N
5'
HO
O
N
N
5
1
N
NH
2
O
guanine
6
OH
O
O
P
O =
P
O
Na
+
NH
2
7
OH
O
8
O
N
N
9
2
O
10
O
cytosine
O
O
P
11
O
N
NH
2
O
12
O
O
N
N
13
3
N
O
H
O
14
adenine
O
H
O
O
P
O
15
O
O
16
O
N
N
4
O
H
3'
thymine
The present review article focuses on DNA damage induced by LEE. DNA
damage is strongly linked to biological radiosensitivity, because of the essential
role played by this molecule in maintaining cellular function. The DNA molecule
consists [
18
] of two long polynucleotide anti-parallel strands composed of repeated
sugar-phosphate units. Four bases are covalently linked to the sugar moiety of the
backbone and hydrogen bonding between the bases holds the two strands together.
The sugar-phosphate backbone of a short DNA strand supporting the four bases
guanine (G), cytosine (C), adenine (A) and thymine (T) is shown in Fig.
1.3
.
According to the example given in Fig.
1.2
, secondary species, generated along
the radiation tracks close to or within DNA can react with this molecule and cause
mutagenic, genotoxic, and other potentially lethal lesions [
19
-
22
]. Because LEE are
the most abundant of the secondary species produced by the primary interaction,
they are expected to play a crucial role in DNA damage.
Review articles on LEE-biomolecule interactions have appeared in the literature
[
23
-
25
]. A complete account of the condensed-phase experimental results on LEE-
induced damage to DNA and its constituents has been published recently by
the author [
26
]. The article contains a description of the relevant experimental
techniques. Quantum mechanical models developed to describe LEE scattering from
DNA and its subunits have also been completely summarized recently [
27
]. The
insertion of theoretical and experimental data into Monte Carlo calculations and
their relationship to radiobiological effectiveness has been reviewed by Nikjoo and
