RESUMO
A combined experimental and theoretical approach has been used to disentangle the fundamental mechanisms of the fragmentation of the three isomers of nitroimidazole induced by vacuum ultra-violet (VUV) radiation, namely, 4-, 5-, and 2-nitroimidazole. The results of mass spectrometry as well as photoelectron-photoion coincidence spectroscopy display striking differences in the radiation-induced decomposition of the different nitroimidazole radical cations. Based on density functional theory (DFT) calculations, a model is proposed which fully explains such differences, and reveals the subtle fragmentation mechanisms leading to the release of neutral species like NO, CO, and HCN. Such species have a profound impact in biological media and may play a fundamental role in radiosensitising mechanisms during radiotherapy.
Assuntos
Nitroimidazóis/química , Processos Fotoquímicos , Isomerismo , Modelos Moleculares , Conformação Molecular , Teoria QuânticaRESUMO
Correction for 'Impact of metallurgical activities on the content of trace elements in the spatial soil and plant parts of Rubus fruticosus L.' by M. M. Nujkicet al., Environ. Sci.: Processes Impacts, 2016, 18, 350-360.
RESUMO
The concentrations of the trace elements (TEs), Cu, Zn, Pb, As, Cd, Ni, were determined in parts of Rubus fruticosus L. and in topsoil, collected from eight different locations around the copper smelter in Bor, Serbia. Extremely high concentrations of Cu were determined in the soil and in R. fruticosus L., and for arsenic at some locations. The enrichment factors for TEs in soil showed enrichment with Cu, Zn, Pb, and As among which extremely high values were determined for Cu (EFsoil = 8.5-126.1) and As (EFsoil = 6.6-44.4). The enrichment factors for the parts of R. fruticosus L. showed enrichment with all TEs, except for nickel. The most extreme enrichment was found to occur in roots and stems for Cu (EFplant = 56.2 and 51.1) and leaves for Pb (EFplant = 45.68). The mean values of the three ratios of concentrations between plant parts for all TEs indicated pollution via the atmosphere while leaves appeared to be the best indicators for this kind of pollution. Numerous and very strong Pearson's correlations between TEs in the R. fruticosus L. parts confirmed these results. Principal Component Analysis showed that the major pollution source is the copper smelter that contaminates vegetation through soil and air.
Assuntos
Arsênio/análise , Metais Pesados/análise , Rubus , Poluentes do Solo/análise , Monitoramento Ambiental , Metalurgia , Folhas de Planta/química , Raízes de Plantas/química , Caules de Planta/química , SérviaRESUMO
The fragmentation of the 2Br-pyrimidine molecule following direct valence photoionization or inner shell excitation has been studied by electron-ion coincidence experiments. 2Br-pyrimidine has been chosen as a model for the class of pyrimidinic building blocks of three nucleic acids and several radiosensitizers. It is known that the site- and state-localization of energy deposition, typical of inner shell excitation, results in the enhancement of the total ion yield as well as in changes in the relative intensity of the different fragmentation channels. Here we address the question of the origin of this selective fragmentation by using electron-ion coincidence techniques. The results show that the fragmentation is strongly selective in the final singly charged ion state, independently of the process that leads to the population of that state, and the dominant fragmentation patterns correlate with the nearest appearance potential.
