One well documented result of UV-B is the appearance of double-strand breaks (DSBs) in DNA [28,18] and pyrimidine dimers
. The cyclobutane pyrimidine dimer
(CPD) (and possibly DSBs) burden resulting from sublethal doses of UV-B may inhibit plant growth and development by slowing transcription and mitosis through imposing energetic costs associated with DNA repair.
Simultaneous establishment of monoclonal antibodies specific for either cyclobutane pyrimidine dimer
or (6-4) photoproduct from the same mouse immunized with ultraviolet-irradiated DNA.
DNA was obtained from plants that were not exposed to UV, with the following exceptions: pea seedlings from the greenhouse, soybean leaves from field-grown plants, and rice seedlings exposed to UV in the laboratory for measurement of pyrimidine dimer
Ultraviolet radiation disrupts the structure of DNA by causing a chemical reaction that hooks together two distinct bases, forming a so-called pyrimidine dimer
. "Pyrimidine dimers
kill cells by blocking DNA replication and transcription," says Hearst, and by causing mutations.
Ultraviolet portion in sunlight is deleterious to the virus activity as it causes DNA and protein matrix degradations (Bandyopadhyay et al., 1999) by producing two types of pyrimidine dimers
; cyclobutane pyrimidine dimers
and pyrimidine-pyrimidine 6-4 photoproducts (Friedberg et al., 1995).
Formation of cyclobutane pyrimidine dimers
at dipyrimidines containing 5-hydroxymethylcytosine.
In fact, it is the first cosmetic ingredient proven to reduce the UV-induced formation of both immediate (iCPDs) and delayed cyclobutane pyrimidine dimers
(dCPDs).Thus, it virtually stops aging before it happens, effectively providing 24/7 skin defense..
Specifically, niacinamide is known to enhance DNA excision repair and repair of UVB-induced cyclobutane pyrimidine dimers
and UVA-induced 8-oxo-7,8-dihydro-2'-deoxyguanosine.
UVB light passing through keratinocytes can cause DNA damage by inducing adjacent pyrimidine bases to form pyrimidine dimers
UV radiation induces DNA damage, such as single-strand breaks, pyrimidine dimers
, and 6-4 PPs, which induce mutations that are characteristic of the promotion, establishment, and development of tumors .
Ultraviolet radiation absorption by DNA molecules results in pyrimidine dimers
as the main direct DNA lesion, while absorption by other molecules causes free radical generation.
Electronic excitation of DNA nucleobases induced by solar ultraviolet light has been extensively studied since the 1960s because it can lead to the formation of harmful photoproducts such as cyclobutane pyrimidine dimers
(CPDs) between adjacent pyrimidine bases within the same DNA strand .