Chapter 5: Photochemistry and Radiation Chemistry of DNA damage, Molecular Mechanisms of DNA damage Flashcards
Humans have ______ cells, typical cell size _______ and typical cell mass ______.
10^14
10 um
1 ng
DNA is ___________, RNA is ___________.
hereditary material of genes
information necessary to build proteins/enzymes.
________ is the principle target for the biological effects of radiation including __________, ___________, and __________.
DNA
cell killing
carcinogenesis
mutation
Minor grooves of DNA are _________, major grooves are _________ and width of DNA is __________.
1.2 nm
1.8 nm
2 nm
The purines are DNA bases ___________ and have ________.
The pyrimidines are DNA bases ____________ and have ________.
adenine and guanine
2 ring
cytosine, thymine and uracil
1 ring
A nucleotide is made up of __________ covalently linked to __________. Nucleotides are covalently linked together in ______________.
sugar-phosphate
base
polynucleotide chains
Because the _____________ is different, we can determine the purity of DNA samples.
absorption spectrum of proteins
A sample of DNA should have ratio A260nm : A280nm equal to ____________ if it is _______.
1.6 - 1.8
pure
????? should it be 0.16-0.18????
The absorption of DNA is due to _________. Because ________ has the lowest triplet state it is the ______________.
bases
thymine
primary candidate for photo-induced changes
UV exposure in wavelength range ________ affects ________, _________ are not directly altered.
bases
sugar-phosphate
The 7 main products found in DNA after absorption of UV at 254 nm are: ___________.
The most important/highest in quantity is __________.
- pyrimidine dimers
- hydrates
- DNA protein crosslinks
- spore photoproducts
- 6-4 pyrimdine adducts
- thymine glycole
- strand breaks
pyrimidine dimers
Absorption of thymine dimer is __________, absorption of irradiated thymine is ________ and absorption of unirradiated thymine is _________.
lowest, medium, high
The excitation energies of singlet states for bases is _________ than the excitation energies of triplet states for bases . ________ has the lowest energy.
higher
thymine
Pyrimidine dimes are chemically __________ and can survive ____________.
extremely stable
acid hydrolysis of DNA
Hydrates are formed by __________ at ________. They are _________ and ___________.
water addition
5-6 double bond of pyrimidine bases
unstable
revert easily with changes in pH or temperature
WRT yield of pyrimidine dimers in mammalian cells __________ has highest yield, then ________, then _________.
6-4 product
protein crosslinks
SSB
6-4 pyrimidine addect has _________ yield than dimers and __________ and may be more important for ___________.
smaller
contributes to lethality
mutations
The 3 classes of compounds that play a role in photosensitization of DNA are __________, __________, and ___________.
halogenated pyrimidines
ketones
furocoumarines
The main halogenated pyrimidine is ___________/____________. It changes the absorption spectrum by __________. Exposure to _________ excites the _________ ultimately leading to ___________.
bromouracil/nucleoside bromodeoxuridine
extending it to longer wavelengths
313 nm
bromouracil
single strand break
The ketones with sensitizing action are _________, __________, and _________ which ___________, leading to ____________. This ultimately leads to ____________.
acetone
acetophenone
benzophenone
absorb UV light beyond 300 nm
triplet excitation with great efficiency
formation of thymine dimers
_________ is a furocoumarin which are important in ___________ and _________. Excitation at _________ causes _____________.
Psoralen
phototherapy
PDT of skin disease
365nm
effects on denaturation behaviour or intracellular DNA replication
4 ways of damaging cellular DNA are __________, __________, __________, and __________.
direct ionization of DNA
reaction with e-pre or e-aq
reactions of OH radicals or H2O+
reactions with other radicals such as O2-. , H2O2, H.
At 10^-16 s, ____________ occurs. Experimental approaches are __________.
excitations and ionization, intratrack reactions
atto-physics, track simulation
At 10^-14 s, ____________ occurs. Can use _________ to measure.
radical formation from radiolysis of water: .OH, e-pre, e-aq, O2.- , H.
femtochemistry, pulse radiolysis
At 10^-12 s, ____________ occurs. Experimental approaches are __________.
ultrafast reactions of radicals
femtochemistry; femtobiology
At 10^-6 s, ____________ occurs. Experimental approaches are __________.
slow reaction of radicals
rapid mix techniques
At 10^0 s, ____________ occurs. Experimental approaches are __________.
enzymic removal of O2.-, H2O2, enzymic repair of damaged molecules
repair deficient cells
At 10^6 s, ____________ occurs. Experimental approaches are __________.
cell proliferation
puck plating techniques
Direct ionization of DNA damages DNA by _____________ which is most probable in ____________.
producing cation radicals
base G through initial ionization of G or from radical transfer to G
Double strand breaks can be caused by either _________ or __________.
a single energy deposition event
interaction of two SSB formed individually in close proximity
The most important lesions produced in chromosomes by radiation is ____________ and may result in ___________.
DSBs
cell killing, carcinogenesis, mutation
MDS are __________ and are produced by _____________. Consist of __________.
multiply damaged sites
cluster of ionizations impinging on DNA
mixtures of lesions
DNA-protein cross links affects ________________ but ____________.
DNA processing at levels of replication, transcription, repair
role of radiation induced DNA protein crosslinks in radiation response still undefined
