Biomedical Engineering Reference
In-Depth Information
Fig. 1.15
X-ray exposure
curves for the loss of the
supercoiled DNA,
a
)in
vacuum on glass and gold
substrates and
b
) under
atmospheric conditions on
glass and gold substrates [
55
].
The points represent the
means of three independent
experiments and the error
bars represent standard
deviation of the means.
(Reprinted with permission
from reference 55. Copyright
2009 American Chemical
Society)
a
VACUUM
on glass
on gold
80
75
70
65
60
55
0 0 0 0 0 0 0 0
Fluence (x10
11
photons/cm
2
)
b
ATMOSPHERE
on glass
on gold
80
75
70
65
60
0
5
10
15
20
25
Fluence (x10
11
photons/cm
2
)
Tabl e 1. 1
cm
2
for the loss of supercoiled DNA in
5 ML films deposited on glass and gold substrates and held under vacuum or atmospheric
conditions. EF is the enhancement factor of the yield in going from glass to gold. G
L
and
G
X
are the G values (number of damages/100 eV) for LEE and X-rays, respectively
Substrate
Percentage yield per
10
12
photons
Environment
Glass
Gold
EF
G
L
G
X
vacuum (V)
2:4 ˙ 0:2
3:4 ˙ 0:3
1.4
4 ˙ 2
0:42 ˙ 0:04
4:7 ˙ 0:5
8:7 ˙ 0:9
6 ˙ 2
0:40 ˙ 0:04
atmosphere (A)
1.9
A/V
2.0
2.6
Fig.
1.15
a, Brun et al. [
55
] estimated the amount of damage produced per units of
energy deposited, usually referred to as the G values.
G
values of
44 ˙ 6
nmol
=
J
(0.42 D/100 eV) were found for 1.5 keV X-rays in vacuum and
J
(4 D/100 eV) for LEE, where D represents one damaged DNA molecule. In the case
400 ˙ 200
nmol
=
