ionizing radiation (IR)


OTHER NAMES:
ionizing radiation


ABBREVIATIONS:
IR


DESCRIPTION: Ionizing radiation is energy that is carried by any of several types of particles and rays (electromagnetic radiation) given off by radioactive material, X-ray machines, and nuclear reactions. This energy can knock electrons out of molecules with which they interact, thus creating ions.
Ionizing radiation is ubiquitous in the environment, and also comes from radioactive materials.

Injury to living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionizing radiation causes atoms and molecules to become ionized or excited. These excitations and ionizations can:
(i) Produce free radicals.
(ii) Break chemical bonds.
(iii) Produce new chemical bonds and cross-linkage between macromolecules.
(iv) Damage molecules that regulate vital cell processes (e.g. DNA, RNA, proteins).

IR has many practical uses in medicine, research, construction, and other areas, but presents a health hazard if used improperly. Exposure to radiation causes damage to living tissue, and can result in mutation, radiation sickness, cancer, and death.


Types of radiation:
Alpha (α) radiation consists of a fast moving helium-4 (4He) nucleus and is stopped by a sheet of paper.
Beta (β) radiation, consisting of electrons, is halted by an aluminium plate.
Gamma (γ) radiation, consisting of energetic photons, is eventually absorbed as it penetrates a dense material.
Neutron (n) radiation consists of free neutrons which are blocked using light elements, like hydrogen, which slow and/or capture them.

DNA DAMAGES:
Tg from Tg:A
T:5-OH-U pair
5,6-dihydroxy U (5,6-diOH-U)
5-hydroxy-6-hydro-T (5-OH-6-H-T)
5-hydroxy-U (5-OH-U)
5-hydroxymethyl U (5-OH-me-U)
8-oxoG
5-OH-meU from 5-OH-meU:A
thymine glycol (Tg)
C:5-OH-U pair
5-OH-meU from 5-OH-meU:G
5-hydroxy-6-hydro-C (5-OH-6-H-C)
5,6-dihydroxy C (5,6-diOH-C)
Tg from Tg:G
5,6-dihydro U (5,6-diH-U)
5-hydroxy C (5-OH-C)
A:5-OH-U pair
G:5-OH-U pair
5-hydroxy-6-hydro-U (5-OH-6-H-U)
5,6-dihydro T (5,6-diH-T)
uracil glycol (Ug)
5-OH-meU in ssDNA
cytosine glycol (Cg)


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NAME STRUCTURE PROTEINS DNA DAMAGE EFFECT(S) PATHWAY(S) RELATED
Tg from Tg:A NTHL1 stalled replication fork base excision repair (BER)
T:5-OH-U pair mutagenesis
point mutation
T→A transversion
transversion
5,6-dihydroxy U (5,6-diOH-U) Nth (endo III)
Ung
Nth (endo III)
Nei (endo VIII)
NEIL1
NEIL2
NTHL1
Nth (endo III)
mutagenesis
point mutation
base excision repair (BER)
5-hydroxy-6-hydro-T (5-OH-6-H-T) Nth (endo III)
Nei (endo VIII)
NTHL1
mutagenesis
point mutation
base excision repair (BER)
5-hydroxy-U (5-OH-U) Nth (endo III)
Fpg (MutM)
Ung
Mug
Nei (endo VIII)
SMUG1
NEIL1
NEIL2
NTHL1
no mutagenesis base excision repair (BER)
5-hydroxymethyl U (5-OH-me-U) AlkA
Mug
Nth (endo III)
Nei (endo VIII)
TDG
Fpg (MutM)
MBD4 (MED1)
SMUG1
mutagenesis base excision repair (BER)
heterochromatin formation
8-oxoG Fpg (MutM)
Nei (endo VIII)
hOGG1
NEIL1
UvrC
UvrB
C→A transversion
G→T transversion
mutagenesis
point mutation
substitution
transversion
base excision repair (BER)
nucleotide excision repair (NER)
prokaryotic (SOS) response
5-OH-meU from 5-OH-meU:A SMUG1 mutagenesis base excision repair (BER)
thymine glycol (Tg) Fpg (MutM)
Nei (endo VIII)
NEIL2
NTHL1
Nth (endo III)
C→T transition
mutagenesis
point mutation
stalled replication fork
substitution
T→C transition
transition
base excision repair (BER)
C:5-OH-U pair mutagenesis
point mutation
5-OH-meU from 5-OH-meU:G SMUG1
MBD4 (MED1)
mutagenesis base excision repair (BER)
heterochromatin formation
5-hydroxy-6-hydro-C (5-OH-6-H-C) Nth (endo III) C→T transition
mutagenesis
point mutation
transition
base excision repair (BER)
5,6-dihydroxy C (5,6-diOH-C) Nth (endo III) C→T transition
mutagenesis
base excision repair (BER)
Tg from Tg:G NEIL1
NTHL1
stalled replication fork base excision repair (BER)
5,6-dihydro U (5,6-diH-U) Nei (endo VIII)
NEIL2
Nth (endo III)
mutagenesis base excision repair (BER)
5-hydroxy C (5-OH-C) Nth (endo III)
Fpg (MutM)
Mug
Nei (endo VIII)
NEIL1
NEIL2
NTHL1
C→T transition
transition
base excision repair (BER)
A:5-OH-U pair no mutagenesis
G:5-OH-U pair G→A transition
mutagenesis
point mutation
transition
5-hydroxy-6-hydro-U (5-OH-6-H-U) Nth (endo III)
Nei (endo VIII)
mutagenesis base excision repair (BER)
5,6-dihydro T (5,6-diH-T) NEIL2
Nei (endo VIII)
Nth (endo III)
Fpg (MutM)
NTHL1
NEIL1
mutagenesis base excision repair (BER)
uracil glycol (Ug) Nth (endo III)
Fpg (MutM)
Nth (endo III)
Nei (endo VIII)
mutagenesis
stalled replication fork
base excision repair (BER)
5-OH-meU in ssDNA SMUG1
MBD4 (MED1)
mutagenesis base excision repair (BER)
heterochromatin formation
cytosine glycol (Cg) NTHL1 C→T transition
transition
base excision repair (BER)

Last modification date: Aug. 28, 2011