Evaluation of DNA-mediated electron transfer using a hole-trapping nucleobase under crowded conditions

The effects of a crowded environment on DNA-mediated electron transfer were evaluated using a pyrene-modified oligonucleotide containing a hole-trapping nucleobase in poly(ethylene glycol) mixed solutions. Rapid decompositions of hole-trapping bases in condensed and noncondensed DNA showed that more efficient electron transfer occurred under crowded conditions than in dilute solutions.

Ectoine interaction with DNA: influence on ultraviolet radiation damage

Ectoine is a small zwitterionic osmolyte and compatible solute, which does not interfere with cell metabolism even at molar concentrations. Plasmid DNA (pUC19) was irradiated with ultraviolet radiation (UV-C at 266 nm) under quasi physiological conditions (PBS) and in pure water in the presence and absence of ectoine (THP(B)) and hydroxyectoine (THP(A)). Different types of UV induced DNA damage were analysed: DNA single-strand breaks (SSBs), abasic sites and cyclobutane pyrimidine dimers (CPDs). A complex interplay between these factors was observed with respect to the nature and occurrence of DNA damage with 266 nm photons. In PBS, the cosolutes showed efficient protection against base damage, whilst in pure water, a dramatic shift from SSB damage to base damage was observed when cosolutes were added. To test whether these effects are caused by ectoine binding to DNA, further experiments were conducted: small-angle X-ray scattering (SAXS), surface-plasmon resonance (SPR) measurements and Raman spectroscopy. The results show, for the first time, a close interaction between ectoine and DNA. This is in stark contrast to the assumption made by preferential exclusion models, which are often used to interpret the behaviour of compatible solutes within cells and with biomolecules. It is tentatively proposed that the alterations of UV damage to DNA are attributed to ectoine influence on nucleobases through the direct interaction between ectoine and DNA.

The effect of spermidine on guanine decomposition via photoinduced electron transfer in DNA

The addition of spermidine caused the attenuation of guanine decomposition via photoinduced electron transfer in pyrene-modified DNA, and higher added concentrations of spermidine resulted in the promotion of decomposition in condensed DNA.

Drastic promotion of guanine oxidation via electron transfer in Ψ-type DNA

Drastic promotion of guanine oxidation was induced by not only intraduplex ET but also interduplex ET in Ψ-type DNA in a crowded environment using PEG.

Inhibiting guanine oxidation and enhancing the excess-electron-transfer efficiency of a pyrene-modified oligonucleotide by introducing an electron-donating group on pyrene

PipPyU and OMePyU enhance the reduction efficiency without oxidizing guanine in DNA-mediated electron transfer.