Lub Mechanism ntawm DNA puas Los ntawm UV Radiation Uvc Dej

Kev ruaj ntseg ntawm DNA yog qhov tseem ceeb heev rau kev ua haujlwm zoo ntawm tag nrho cov txheej txheem ntawm tes. Kev raug UV hluav taws xob hloov pauv cov qauv ntawm DNA, cuam tshuam rau cov txheej txheem physiological ntawm tag nrho cov kab mob nyob xws li kab mob mus rau tib neeg.

Ultraviolet hluav taws xob

Lub hnub ci ntuj txhawb kev tsim cov vitamin D, uas yog ib qho tseem ceeb rau kev tsim cov pob txha noj qab haus huv. Txawm li cas los xij, hnub ci kuj yog qhov tseem ceeb ntawm UV hluav taws xob. Cov tib neeg uas tau txais UV ntau dhau yog qhov txaus ntshai ntawm kev tsim cov qog nqaij hlav ntawm daim tawv nqaij. Muaj peb hom UV rays: UVA, UVB thiab UVC.

• UVC rays (100-280 nm) yog lub zog tshaj plaws thiab kev puas tsuaj ntawm peb lub rays. Hmoov zoo, UVC yog absorbed los ntawm ozone txheej ua ntej mus txog lub ntiaj teb nto.

• UVA rays (315-400 nm) muaj lub zog qis tshaj plaws thiab muaj peev xwm nkag mus tob rau hauv daim tawv nqaij. Kev raug mob ntev tau txuas rau kev laus thiab wrinkling ntawm daim tawv nqaij. UVA kuj tseem yog qhov ua rau melanomas.

• UVB rays (280-315 nm) muaj lub zog ntau dua li UVA rays thiab cuam tshuam rau txheej txheej ntawm daim tawv nqaij ua rau sunburns thiab tans. Basal cell carcinoma thiab squamous cell carcinoma yog tshwm sim los ntawm UVB hluav taws xob.

DNA yog tsim los ntawm ob txoj hlua txuas ntxiv uas raug mob rau hauv ob lub helix. Cov kab lus keeb kwm yog tshuaj lom neeg thiab tsim los ntawm plaub nucleotides adenine (A), thymine (T), guanine (G) thiab cytosine (C).

UVB teeb cuam tshuam ncaj qha rau kev sib txuas ntawm nucleotides hauv DNA. Ob qhov chaw DNA tseem ceeb tsim los ntawm kev raug UVB yog cyclobutane pyrimidine dimers (CPD) thiab 6-4 pyrimidine pyrimidone photoproducts (6-4PPs), thiab nws cov Dewar isomers.

CPDs tau tsim thaum ob lub hauv paus pyrimidine uas nyob ib sab (thymine -TT lossis cytosine - CC) ua cov sib txuas ua ke uas tsim cov qauv voj voog. 6-4PPs tshwm sim los ntawm ib qho kev sib cog lus tsim los ntawm 5' kawg ntawm C6 thiab 3' kawg ntawm C4 ntawm pyrimidines uas nyob ib sab. Qhov no ua rau muaj qhov tsis ruaj khov oxetane lossis azetidine nruab nrab nyob ntawm seb lub hauv paus 3' kawg yog thymine lossis cytosine.

Tom qab kev hloov pauv ntawm cov khoom nruab nrab no ua rau nce mus rau 6-4PP. Cov pyrimidine dimers ua rau kink nyob rau hauv DNA caj qaum, halting transcription thiab protein synthesis. 6-4 pyrimidine pyrimidone adducts undergo isomerization rau lawv daim ntawv Dewar thaum raug lwm photon ntawm lub teeb los ntawm UVB los yog UVA hluav taws xob. Qhov kev hloov pauv ntau tshaj plaws los ntawm UVB yog C rau T transversion. Ob chav hloov pauv (CC rau TT) kuj tshwm sim, txawm tias tsawg zaus.

UVA (thiab kuj UVB) hluav taws xob ua rau kev puas tsuaj rau DNA ntawm kev nqus ntawm photons los ntawm non-DNA chromophores. Qhov no tsim cov pa oxygen reactive xws li singlet oxygen lossis hydrogen peroxide uas oxidize DNA bases ua rau kev hloov. Kev hloov pauv ntau tshaj plaws yog GT kev hloov pauv uas guanine tau oxidized rau hauv 8-oxo- 7,8-dihydroguanine (8-oxoG) cuam tshuam nws txoj kev ua ke nrog cytosine. Thaum lub sij hawm replication txheej txheem, 8-oxoG khub nrog adenine. Thaum lub thib ob strand yog synthesized, 8-oxoG yog hloov nrog ib tug thymine ua rau ib tug GT transversion.

DNA Kho

Cov kab mob caj ces tsim los ntawm UV hluav taws xob feem ntau kho sai tom qab lawv tsim, los ntawm cov txheej txheem hu ua nucleotide excision kho. Lub nuclease enzyme paub thiab tshem tawm ib ntu ntawm DNA uas muaj qhov txhab. Tom qab ntawd, cov polymerase ntxig cov hauv paus kom raug thiab ligase kaw qhov sib txawv. Txawm li cas los xij, yog tias tsis kho qhov txhab sib sau los yog cov txheej txheem kho tsis raug, nws tuaj yeem ua rau cell tuag, mutagenesis thiab txawm tias mob qog noj ntshav.