Structures and Electron Attachment Properties of Halomethanes (CX n Y m,X = H,F; Y = Cl,Br, I; n = 0,4; m = 4n)

Abstract

Theoretical studies of structures of neutral molecules and their anions as well as dissociative electron attachment properties are presented for the halomethanes of general formula CX _n Y _m ; X = H, F; Y = Cl, Br, I; n = 0,4; m = 4 – n. The dissociative electron attachment seems to be the primary process resulting in toxicity of these species. The halomethane anions containing hydrogens are formed as radical-anion adducts. When H is replaced by F, these species become true σ? radicals. The electron affinities are computed using a variety of computational techniques including the four-order M?ller-Plesset (MP4) technique that included 250 basis functions. It is challenging to compare the computed results with experiment due to dearth of experimental data and uncertainties in the existing experimental data. Thus in certain cases larger differences are found between the computed and experimental values.     

手印纳米显现效果的评价研究进展

近些年来,将量子点、金属及金属氧化物纳米材料、稀土上转换及下转换发光纳米材料、荧光碳点、金属-有机框架材料、聚集诱导发光材料等新型材料应用于手印显现领域的研究日益增多,由此衍生出一类新兴的手印显现技术--手印纳米显现技术。手印纳米显现技术具有操作简单、方法灵活、效果显著、适用广泛等突出优势,已经成为传统手印显现技术的重要补充。国内外研究人员对手印纳米显现技术的探索主要集中在显现材料的推陈出新和显现方法的交叉融合两方面,而对手印显现效果的影响因素及综合评价等研究却较为分散且缺乏系统性。准确客观地评价手印纳米显现效果对于显现方法的合理选择和物证价值的客观评估都具有非常重要的意义。该综述从对比度、灵敏度、选择性、毒害性等四方面对手印显现特别是手印纳米显现的效果评价方法进行梳理总结,并对影响手印纳米显现效果的诸多因素分别进行讨论。纳米材料的发光性质主要决定了手印显现的对比度,纳米材料的微观形貌和颗粒尺寸主要决定了手印显现的灵敏度,纳米材料的吸附性能和表面性质主要决定了手印显现的选择性,因此可通过调整显现材料的诸多性质来提升改善手印纳米显现的效果。最后,对手印纳米显现未来的发展方向提出全新展望。纳米显现材料必然由单一发光性能向多元发光性能过渡,由现有材料的借鉴使用向形貌尺寸的精细操控过渡,由表面简单处理向靶向分子修饰过渡,由潜在毒害材料向绿色环保材料过渡;纳米显现方法必然由强背景干扰向弱背景干扰发展,由细节特征的清晰显现向汗孔特征的清晰显现发展,由物理吸附向靶向识别发展,由痕迹物证的高效显现向生物物证的微观无损发展。同时建议科研人员在注重提升手印显现效果的同时,更加重视对手印显现效果的定量评价研究,进而促进手印纳米显现技术体系的完善,也可使手印纳米显现技术在刑事科学技术领域中发挥出重要的作用。     

Study on the toxic interactions of Ni with DNA using neutral red dye as a fluorescence probe

The interaction between Ni²⁺ and calf thymus DNA (ctDNA) was investigated in simulated physiological buffer (pH 7.4) using the Neutral Red (NR) dye as a spectral probe by UV-vis absorption and fluorescence spectroscopy, as well as CD spectra. The experimental results showed that the conformational changes in DNA helix induced by Ni²⁺ are the reason for the fluorescence quenching of the DNA-NR system. From the experimental results, conclusion can be drawn that Ni²⁺ can cause structural changes of ctDNA and bind with DNA by electrostatic interaction. At the same time, the paper proved that conformation changes of DNA can also lead to the fluorescence decrease of DNA-probe systems.     

雕白粉与食品亚硫酸盐漂白剂

本文分析了目前社会上反应强烈的在食品中所添加的雕白粉的毒性 ,对食品工业中使用的亚硫酸及其盐类漂白剂的漂白、抗氧化、防腐及可能的毒副作用进行了综述。     

The distribution and potential toxic effects of TBT in UK estuaries during 1986

The concentrations of butyltin compounds in seawater were measured at nine sites in the UK during 1986. In popular yachting centres concentrations of tributyltin (TBT) ranged from less than detectable ( < 1 ng dm^?3) in the winter, up to 1500 ng dm^?3 in marinas in the summer. Measurements of wastewater generated by high-pressure hosing of yachts demonstrated that even higher environmental concentrations of TBT resulted from the procedure. The results of the monitoring programme are discssed in relation to the toxicity of TBT and recent government legislative actions.     

Environmental aspects of tributyltin

The tributyltin species, the active ingredient in some antifouling paint formulations, is perhaps the most acutely toxic chemical to aquatic organisms ever deliberately introduced to water. It has been demonstrated to have an adverse effect on shellfish in France and England, and as a consequence the use of tributyltin-containing antifouling paints has been restricted in these countries. Other countries have banned the use of tributyltin-containing antifouling paints or are contemplating restrictions. This article reviews such environmental aspects of tributyltin as methods of analysis, toxicity, environmental occurrence, persistence and fate. Tributyltin concentrations in many locations may be high enough to cause chronic toxicity or harmful effects in some aquatic organisms, and in some locations the tributyltin concentrations may be high enough to be acutely toxic to some organisms. Biological degradation of tributyltin in water and sediment appears to be the most important factor limiting the persistence of tributyltin in aquatic environments. To some degree, then, the persistence of tributyltin in aquatic environments depends upon the nature of the ecosystem. Tributyltin exhibits low-to-medium persistence in water and moderate persistence in sediment. A summary is given of the regulatory status of tributyltin in some countries, and recommendations are made for further research.     

Isolation of toxic compounds from wild Phaeocystis globosa

Two new compounds, namely taenialactam C and globorin A (1 and 2), as well as six known compounds, cornoside (3), 2-phenylethyl-b-D-glucoside (4), 3-isopropyl-5-acetoxycyclohexene-2-one-1 (5), 4-methyl-phenol (6), 5-[(2S)-2-aminobutyl]-2-methyl-phenol (7), and 1-(4-methylphenyl)-1-propanone (8) were isolated from wild Phaeocystis globosa. The structures of the new compounds were established by detailed spectroscopic analysis and by comparison with spectral data of related known compounds. The structures of the known compounds were identified by comparing their spectroscopic data with those reported in the literature. This paper also reports toxicity properties of the eight compounds against the brine shrimp Artemia salina and juvenile Epinephelus akaara fish. Some of these compounds showed significant lethality on the brine shrimp A. salina and the juvenile E. akaara fish.     

Assessment of the acute toxicity of triclosan and methyl triclosan in wastewater based on the bioluminescence inhibition of Vibrio fischeri

In this work, the contributions of triclosan and its metabolite methyl triclosan to the overall acute toxicity of wastewater were studied using Vibrio fischeri. The protocol used in this paper involved various steps. First, the aquatic toxicities of triclosan and methyl triclosan were determined for standard substances, and the 50% effective concentrations (EC₅₀) were determined for these compounds. Second, the toxic responses to different mixtures of triclosan, methyl triclosan, and surfactants were studied in different water matrices, i.e., Milli-Q water, groundwater and wastewater, in order to evaluate (i) the antagonistic or synergistic effects, and (ii) the influence of the water matrices. Finally, chemical analysis was used in conjunction with the toxicity results in order to assess the aquatic toxicities of triclosan and its derivative in wastewaters. In this study, the toxicities of 45 real samples corresponding to the influents and effluents from eight wastewater treatment works (WWTW) were analyzed. Thirty-one samples were from a wastewater treatment plant (WWTP) equipped with two pilot-scale membrane bioreactors (MBR), and the influent and the effluent samples after various treatments were characterized via different chromatographic approaches, including solid-phase extraction (SPE), liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS), and SPE coupled to gas chromatography–mass spectrometry (GC–MS). The toxicity was determined by measuring the bioluminescence inhibition of Vibrio fischeri. In order to complete the study and to extrapolate the results to different WWTPs, the toxicity to V. fischeri of samples from seven more plants was analyzed, as were their triclosan and methyl triclosan concentrations. Good agreement was established between the overall toxicity values and concentrations of the biocides, indicating that triclosan is one of the major toxic organic pollutants currently found in domestic wastewaters.     

Characterization of an epoxide‐derived metabolite of dictamnine using high‐performance liquid chromatography with hybrid linear trap quadrupole orbitrap mass spectrometry

Dictamnine (4‐methoxyfuro[2,3‐b]quinolone), a furoquinoline alkaloid of the Rutaceae plant family, has been reported to be a phototoxic and photomutagenic compound, whose exposure can cause carcinogenicity, cytotoxicity, and genotoxicity. Metabolic activation is suggested to play an important role in dictamnine‐induced toxicities, and the epoxide metabolite of dictamnine has been reported to be the main intermediate in vitro. The objective of this study was to identify N‐acetylcysteine conjugate(s) derived from this reactive dictamnine metabolite in vitro and in vivo. An N‐acetylcysteine conjugate of dictamnine was detected in microsomal incubations of dictamnine, as well as bile and urine samples of rats treated with dictamnine. The data obtained from the present work will facilitate the understanding of the mechanism behind dictamnine‐induced toxicities.