RESUMO
Hydrogen peroxide (H2O2) is a unique molecule that is applied in various fields, including energy chemistry, astrophysics, and medicine. H2O2 readily forms clusters with water molecules. In the present study, the reactions of ionized H2O2-water clusters, H2O2 +(H2O) n , after vertical ionization of the parent neutral cluster were investigated using the direct ab initio molecular dynamics (AIMD) method to elucidate the reaction mechanism. Clusters with one to five water molecules, H2O2-(H2O) n (n = 1-5), were examined, and the reaction of [H2O2 +(H2O) n ]ver was tracked from the vertical ionization point to the product state, where [H2O2 +(H2O) n ]ver is the vertical ionization state (hole is localized on H2O2). After ionization, fast proton transfer (PT) from H2O2 + to the water cluster (H2O) n was observed in all clusters. The HOO radical and H3O+(H2O) n-1 were formed as products. The PT reaction proceeds directly without an activation barrier. The PT times for n = 1-5 were calculated to be 36.0, 9.8, 8.3, 7.7, and 7.1 fs, respectively, at the MP2/6-311++G(d,p) level, indicating that PT in these clusters is a very fast process, and the PT time is not dependent on the cluster size (n), except in the case of n = 1, where the PT time was slightly longer because the bond distance and angle of the hydrogen bond in n = 1 were deformed from the standard structure. The reaction mechanism was discussed based on these results.
RESUMO
From 1990 to 2008, 9 food poisoning incidents due to ingestion of marine boxfish occurred in Nagasaki, Miyazaki, Mie and Kagoshima Prefectures, Japan, and a total of 13 persons were poisoned. Their main symptom was severe muscle pain arising from rhabdomyolysis, which was usually accompanied by the discharge of black urine and abnormal elevation of serum creatine phosphokinase. Twelve out of the 13 victims recovered in a few days to two months, while one died after approximately 2 weeks. Since the symptoms were very similar to those caused by parrotfish "aobudai" Scarus ovifrons poisoning, the causative substance was considered to be parrotfish toxin, i.e., a palytoxin-like substance. Epidemic surveys after the incidents in Miyazaki and Nagasaki identified the leftovers as "hakofugu" Ostracion immaculatus. During screening tests to clarify the toxicity of boxfish from Western Japan, 47 of 129 specimens (36.4%) of O. immaculatus, and 7 of 18 specimens (38.9%) of "umisuzume" Lactoria diaphana were found to show acute and/or delayed lethal activity to mice (0.5-2.0 mouse unit/g). Among the tissues tested, the frequency of toxicity was highest in the viscera excluding liver (28.6% in O. cubicus, 33.3% in L. diaphana), followed by muscle (10.9%, 5.6%) and liver (6.2%, 5.6%). From the above results, we conclude that O. cubicus and L. diaphana inhabiting the coast of Japan sometimes contain toxic substance(s), which can sporadically cause food poisonings very similar to parrotfish poisoning.
