Changes in the circular dichroic spectrum of calf thymus solubilized chromatin caused by ultraviolet irradiation

Abstract

UV irradiation of the chromatin caused an increase of the positive circular dichroic band in the vicinity of 275 nm (corresponding to DNA) and a deepening of the negative band of proteins at about 225 nm. These changes in the circular dichroic spectrum are monotonous in the range of doses studied (less than 6 X 10(4) J.m-2). The increase of the positive circular dichroic band probably reflects the occurrence of local conformational changes in DNA, which include changes in base position (tilting, distance from helix axis) in the close neighborhood of photoproducts. The presence of photoproducts in chromatin reduces changes in its circular dichroic spectra with temperature.

UV-induced pyrimidine dimers and trimethylpsoralen cross-links do not alter chromatin folding in vitro

“…In the case of PD, there is good agreement on the degree of DNA helix unwinding and distortion caused by these adducts (see the introduction). Alterations in DNA structure by PD are also observed on the basis of changes in sedimentation (Marmur et al, 1961), thermal denaturation (Marmur et al, 1961), and CD spectra (Vorlickova et al, 1979;Lang & Luck, 1973). Indeed, the CD data presented in Figure 7 support these findings.…”

“…Since it was apparent from these experiments that damage by UV light at 254 nm had little or no effect on salt-induced chromatin folding, even at the extremely large dose of 20000 J/m2, it was of interest to determine if changes in DNA secondary structure could be detected in UV-irradiated chromatin (Vorlickova et al, 1979). To this end, we performed circular dichroism (CD) measurements on chromatin fibers irradiated with different UV doses.…”

Electrochemical Sensors for DNA Interactions and Damage

“…Intact native DNA produced only a very small cathodic peak (peak II) in differential pulse polarography [21 ± 23]. Intensity of this signal was, however, very sensitive to small changes in DNA structure, such as DNA premelting [21], introduction of single-strand breaks (ssb) [22, 89 ± 91] or damage to DNA induced by UV-radiation [90] and by chemical agents reacting with DNA base residues, including cisplatin [92] or osmium tetroxide complexes [93]. Adsorption/desorption behavior of DNA at the mercury electrodes ( Fig.…”

“…Photoexcitation of DNA bases may lead to a number of reaction products, including photohydrates, pyrimidine dimers [1,30,90] or purine degradation products such as 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua) [123]. Electrochemical properties of monomeric pyrimidine and purine photoadducts at mercury electrodes were studied by Czochralska et al [124,125].…”

“…Electrochemical properties of monomeric pyrimidine and purine photoadducts at mercury electrodes were studied by Czochralska et al [124,125]. Changes in electrochemical behavior of calf thymus dsDNA upon irradiation with UV light were detected by means of DPP [90]. Wang et al constructed a microfabricated screenprinted electrode-based DNA sensor responding to UV radiation-induced damage to guanine residues [123].…”