Ultrafast Processes Occurring in Radiolysis of Highly Concentrated Solutions of Nucleosides/Tides

Abstract

Among the radicals (hydroxyl radical (•OH), hydrogen atom (H•), and solvated electron (esol−)) that are generated via water radiolysis, •OH has been shown to be the main transient species responsible for radiation damage to DNA via the indirect effect. Reactions of these radicals with DNA-model systems (bases, nucleosides, nucleotides, polynucleotides of defined sequences, single stranded (ss) and double stranded (ds) highly polymeric DNA, nucleohistones) were extensively investigated. The timescale of the reactions of these radicals with DNA-models range from nanoseconds (ns) to microseconds (µs) at ambient temperature and are controlled by diffusion or activation. However, those studies carried out in dilute solutions that model radiation damage to DNA via indirect action do not turn out to be valid in dense biological medium, where solute and water molecules are in close contact (e.g., in cellular environment). In that case, the initial species formed from water radiolysis are two radicals that are ultrashort-lived and charged: the water cation radical (H2O•+) and prethermalized electron. These species are captured by target biomolecules (e.g., DNA, proteins, etc.) in competition with their inherent pathways of proton transfer and relaxation occurring in less than 1 picosecond. In addition, the direct-type effects of radiation, i.e., ionization of macromolecule plus excitations proximate to ionizations, become important. The holes (i.e., unpaired spin or cation radical sites) created by ionization undergo fast spin transfer across DNA subunits. The exploration of the above-mentioned ultrafast processes is crucial to elucidate our understanding of the mechanisms that are involved in causing DNA damage via direct-type effects of radiation. Only recently, investigations of these ultrafast processes have been attempted by studying concentrated solutions of nucleosides/tides under ambient conditions. Recent advancements of laser-driven picosecond electron accelerators have provided an opportunity to address some long-term puzzling questions in the context of direct-type and indirect effects of DNA damage. In this review, we have presented key findings that are important to elucidate mechanisms of complex processes including excess electron-mediated bond breakage and hole transfer, occurring at the single nucleoside/tide level.

Structure of the Bacterial Ribosome at 2 Å Resolution

“…Radiation damage to nucleic acids has been extensively studied because of its clinical relevance. Experiments using high-energy X-ray or electron pulses showed damage to be caused principally by low-energy secondary electrons rather than as a direct result of irradiation (Ma et al, 2019). In our structure evidence for such damage appears as a clear break in the ring density for numerous riboses and is generally surrounded by otherwise strong density for bases, phosphates, and amino acids.…”

Ne-22 Ion-Beam Radiation Damage to DNA: From Initial Free Radical Formation to Resulting DNA-Base Damage

“… 2 , 3 , 13 − 17 C1′ • , C3′ • , and C5′ • are produced by (a) ionization of 2′-deoxyribose, followed by deprotonation, 2 , 3 , 13 − 17 , 42 (b) charge and spin transfer from the excited base cation radicals to 2′-deoxyribose-producing cation radicals of 2′-deoxyribose, followed by deprotonation, 2 , 3 , 13 , 14 , 42 and (c) phosphate-to-2′-deoxyribose hole transfer, followed by deprotonation. 42 , 43 On the other hand, the formation of C3′ • dephos is associated with a radiation-produced low-energy electron-mediated dissociative electron attachment process. 2 , 3 , 13 − 17 , 41 …”

“…The fact that the yields of these products in Ne-22 beam-irradiated hydrated DNA are much lower than those of Gua-derived lesions ( Table S3 ) may point to the fast hole transfer from T •+ and C •+ to Gua. 2 − 4 , 13 , 38 − 40 , 42 …”

Extracellular vesicle‐enclosed miR‐486‐5p mediates wound healing with adipose‐derived stem cells by promoting angiogenesis

“…21 Besides, human ASCs are found in subcutaneous adipose tissues. 22 Thus, amongst the established-cutaneous wound healing strategies, adipose tissues are widely used for treatment options associated with the skin tissue regenerative medicine. 23 In addition to its extensive application in wound healing, the positive impact of ASC-derived EVs has also been discovered on angiogenesis or vascularization.…”