Multiple magnetic bilayers and unconventional criticality without frustration in BaCuSiO

Allenspach, S.*; Biffin, A.*; Stuhr, U.*; Tucker, G. S.*; Kawamura, Seiko; Kofu, Maiko; Voneshen, D. J.*; Boehm, M.*; Normand, B.*; Laflorencie, N.*; et al.

Physical Review Letters, 124(17), p.177205_1 - 177205_7, 2020/05

https://doi.org/10.1103/PhysRevLett.124.177205

Chemical repair activity of free radical scavenger edaravone; Reduction reactions with dGMP hydroxyl radical adducts and suppression of base lesions and AP sites on irradiated plasmid DNA

Hata, Kuniki; Urushibara, Ayumi*; Yamashita, Shinichi*; Lin, M.*; Muroya, Yusa*; Shikazono, Naoya; Yokoya, Akinari; Fu, H.*; Katsumura, Yosuke*

Journal of Radiation Research, 56(1), p.59 - 66, 2015/01

AA2014-0383.pdf:0.93MB

https://doi.org/10.1093/jrr/rru079

Fast repair activities towards dGMP hydroxyl radical adducts by silybin and its analogues

Fu, H.*; Katsumura, Yosuke; Lin, M.; Hata, Kuniki; Muroya, Yusa*; Hatano, Yoshihiko

Journal of Radiation Research, 49(6), p.609 - 614, 2008/11

https://doi.org/10.1269/jrr.08056

The repair activities of silybin (SLB) and its analogues towards the oxidizing deoxyguanosine monophosphate (dGMP) hydroxyl radical adducts are investigated by pulse radiolytic techniques. On pulse irradiation of nitrous oxide saturated 2.0 mM dGMP aqueous solution containing 0.1 mM silybin at neutral pH, the transient absorption spectrum of the dGMP hydroxyl radical adducts decreases with the formation of the phenoxyl radical of silybin within tens of microseconds, indicating that there is a repair reaction between the dGMP hydroxyl radical adduct and silybin. The rate constant of the repair reaction is calculated to be 1.010 Ms for silybin. The repair activity of hesperetin (HESP), naringin (NAN) and naringenin (NAR) towards hydroxyl radical adducts of dGMP are also studied.

Bioflavonoids as antiradicals, antioxidants and DNA cleavage protectors

Fu, H.*; Lin, M.; Katsumura, Yosuke; Muroya, Yusa*; Hata, Kuniki

no journal, , 

Flavonoids, which are categorized as natural poly-phenolic compounds, have been reported to have antiviral, antiallergic, anti-infammatory and antitumoral activities, and their pharmacological properties have been ascribed both to the concomitant inhibition of enzymes involved in the production of free radicals and to their free-radical scavenging and iron chelating capacity. However their antioxidant capacities are still controversial. In this study, free-radical scavenging capacities of bioflavonoids were investigated using nano-second pulse radiolysis technique. Transient spectra and kinetics of transient species induced by hydroxyl radicals and other specific oxidants like dibromine radicals and azide radicals were observed. In addition, their abilities to protect DNA from radiation-induced damages was also investigated by conducting gel-electrophoresis analysis of X-ray-irradiated sample solutions consisting of pUC18 DNA as well as the flavonoids.

"" DNA protective properties of Silybin and analogues against X-ray radiation

Fu, H.*; Lin, M.; Hata, Kuniki; Muroya, Yusa*; Fujii, Kentaro; Katsumura, Yosuke; Yokoya, Akinari; Shikazono, Naoya; Hatano, Yoshihiko

no journal, , 

Natural flavonoids such as silybin (SLB) are believed to be active constituents of plants accounting for the reported chemoprevention of certain cancers. However, molecular mechanisms by which the low-concentration SLB and analogues in human can reduce the incidence are not clear. Using an plasmid DNA system with radiolytically generated reactive oxygen species (ROS) under constant scavenging conditions, it was shown that the tested flavonoids can ameliorate free radical damage sustained by DNA. The dose modifying factor for 0.1 mM SLB for 50% protection of plasmid DNA was found to be 8.9. SLB was the most active among the tested flavonoids, with effects seen at M. Combined fast-reaction chemistry studies support a mechanism of electron transfer (or H-atom transfer) from SLB to ROS-induced radical sites on DNA. These results support an antioxidant role for SLB and analogues in the direct interaction with DNA radicals.

High temperature-ultrafast pulse radiolysis

Muroya, Yusa*; Lin, M.; Han, Z.*; Fu, H.*; Yamashita, Shinichi; Sakumi, Akira*; Ueda, Toru*; Katsumura, Yosuke

no journal, , 

In order to investigate radiation-induced fast phenomena in solutions such as water and alcohols at extreme conditions (high temperature and pressure), a new high temperature-ultrafast pulse radiolysis system was developed, which was previously applicable only to the experiment at ambient condition. After the setup of the pulse radiolysis system a preliminary experiment, transient absorption spectroscopy of hydrated electron within a few nanosecond at elevated temperature from room temperature up to 300 C, was performed.

A Study on antioxidative property of edaravone derivatives by pulse radiolysis

Hata, Kuniki; Katsumura, Yosuke; Lin, M.; Muroya, Yusa*; Fu, H.*; Kudo, Hisaaki*; Nakagawa, Keiichi*; Nakagawa, Hidehiko*

no journal, , 

The reactivity of edaravone with some oxidative radicals (OH, N, Br, SO, CClOO) has been measured by pulse radiolysis. The reaction product of edaravone with OH was different from those with other radicals. The rate constants of edaravone derivatives with OH have also been determined by both direct measurement and a competition method using CO and DMPO as competitors.

A Study on the reactivity of edaravone derivatives by pulse radiolysis

Hata, Kuniki; Katsumura, Yosuke; Lin, M.; Muroya, Yusa*; Fu, H.*; Kudo, Hisaaki*; Nakagawa, Keiichi*; Nakagawa, Hidehiko*

no journal, , 

no abstracts in English

A Comparative study on the free radical scavenging reactivity of edaravone and its derivatives

Hata, Kuniki; Katsumura, Yosuke; Lin, M.; Muroya, Yusa*; Fu, H.*; Yamashita, Shinichi; Kudo, Hisaaki*; Nakagawa, Keiichi*; Nakagawa, Hidehiko*

no journal, , 

Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), which is clinically used for brain infarct in Japan from 2001, is a potent antioxidative medicine. Edaravone is also expected as a radioprotector for its high reactivity towards oxidizing radicals. Recently, some edaravone derivatives have been being investigated in order to study the Structure Activity Relationship (SAR) and to seek for more efficient radioprotector(s) other than edaravone. It was reported that a derivative with a pyridine ring as a substitute had much higher reactivity with hydroxyl radical than edaravone. However, the early processes of the reactions of edaravone derivatives are not fully understood and the quantitative data about their reaction rate have not been determined. In this study we investigated the reactions between some edaravone derivatives and hydroxyl radical and determined the rate constants of these reactions by pulse radiolysis technique. The rate constants were measured by three different methods. The first was direct measurement from the buildup kinetics of transient radicals. The second was competition method using carbonate ion as a competitor. The third was competitive measurement using DMPO, which is widely used spin-trapping agent for hydroxyl radical or hydrogen atom. The experimental results showed high reactivity of all derivatives investigated in this study. These reactions are near diffusion controlled. Moreover, the rate constants of derivatives with a pyridine ring by competition with DMPO were estimated twice as high as that by direct measurement. A possible interaction between the pyridine ring and DMPO is proposed.

A Study on the free radical scavenging mechanism of edaravone

Hata, Kuniki; Katsumura, Yosuke; Lin, M.; Muroya, Yusa*; Fu, H.*; Yamashita, Shinichi; Kudo, Hisaaki*; Nakagawa, Keiichi*; Nakagawa, Hidehiko*

no journal, , 

Edaravone or RadiCut, 3-methyl-1-phenyl-2-pyrazolin-5-one, is a developed free radical scavenger that has been approved in Japan as a neuroprotective drug since 2001. For its antioxidative property and high reactivity with free radicals, edaravone has been expected as a radioprotector. In the last decade, the reactivity of edaravone with peroxyl radicals or some enzymes which induce oxidizing reactions, as well as the antioxidative properties of edaravone, have been extensively investigated. However, there are only a few reports on the measurements of the reactivity of edaravone towrads OH radical, although OH radical is thought to be a main factor of indirect radiation induced damages. In this work, we measured the reactivity of edaravone with OH radical, and elucidated its reaction mechanism. The reactions of edaravone and its model compound (1,3-dimethyl-2-pyrazolin-5-one) with OH radical or other oxidizing radicals were measured by pulse radiolysis techniques. The result shows that the intermediate radical produced by the reaction of edaravone with OH radical was spectroscopically different from that by the reactions with other radicals. On the other hand, for 1,3-dimethyl-2-pyrazolin-5-one, the intermediate radical by the reaction with OH radical is similar to that by the reaction with other oxidizing radical. All these strongly suggest that the phenyl group of edaravone plays an important role on the reaction with OH radical. Thus, in contrast to the previous reports in which the oxidation by OH radical was assumed to be through electron transfer or hydrogen abstraction from pyrazolin-5-one, the formation of OH adducts is crucial for the reaction of edaravone towards OH radical.