三苯基锡化合物与DNA作用的光谱研究

研究了船体防污漆中主要防污成分-三苯基一氯化锡(TPTC1)与DNA作用的光谱性质.结果表明,TPTCl对DNA的作用是双重的,也就是既可作用于DNA的碱基,对DNA双螺旋结构有一定影响;也可作用于DNA的磷酸基团,使DNA构象发生变化.主要表现在作用时间不同,则作用位点也不同.短时间内,作用位点是DNA的碱基,紫外光谱表现为增色效应;长时间时,作用位点转到了DNA的磷酸基团,紫外光谱表现为减色效应.另外,考察了不同缓冲溶液体系对TPTCl与DNA作用光谱的影响.紫外光谱表明,Tris-HCl和KH2PO4-NaOH体系减弱了TPTCl与DNA的作用,而HAc-NaAc体系则增强了TPTCl与DNA的作用.     

三丁基锡化合物与牛血清白蛋白相互作用的光谱研究

通过紫外光谱（UV）和圆二色光谱（CD），研究了三丁基锡（TBT）化合物与牛血清白蛋白（BSA）的相互作用以及浓度变化对TBT与BSA相互作用的影响。结果表明，TBT与BSA的相互作用是双重的。既有TBT中锡离子与BSA的配位作用，又有TBT中丁基的疏水作用，引起BSA构象变化和叶螺旋结构的改变。     

丁基锡系列化合物与脱氧核糖核酸的相互作用

通过紫外（ultraviolet,UV）光谱和圆二色（circular dichroism,CD）光谱,研究了丁基锡化合物（一丁基锡、二丁基锡和三丁基锡）与脱氧核糖核酸（deoxyribonucleic acid,DNA）的作用方式以及时间和浓度的影响。结果显示丁基锡化合物与DNA的作用是双重的,既作用于DNA的碱基,对双螺旋结构有一定影响,又作用于DNA的磷酸基团,使构象发生变化。但是,丁基锡化合物与脱氧核糖核酸作用的程度和方式与丁基锡种类、时间和浓度等因素有关。一丁基锡倾向于与磷酸基团作用,三丁基锡倾向于与碱基作用,而二丁基锡与两者作用程度相近。短时间内,丁基锡化合物的作用位点通常是DNA的碱基;长时间时,则作用位点往往是DNA的磷酸基团。低浓度的丁基锡化合物倾向与DNA的碱基结合,高浓度的丁基锡化合物倾向与DNA的磷酸基团结合。     

丁基锡化合物与人血清白蛋白相互作用的研究

通过紫外、荧光和CD光谱, 研究了船体防污漆中主要防污成分——三丁基锡(TBT)化合物及其降解产物——一丁基锡(MBT)和二丁基锡(DBT)与人血清白蛋白(HSA)相互作用的方式与程度, 考察了浓度、酸度、有机溶剂和离子强度等因素对相互作用的影响. 结果表明, 丁基锡与HSA的相互作用是双重的, 既有丁基锡中锡离子与HSA的配位作用, 又有丁基锡中丁基基团的疏水作用, 导致HSA二级结构破坏, α-螺旋结构减少和构象转变. 一般情况下, MBT以配位作用为主, TBT以疏水作用为主, DBT两者兼而有之.     

含席夫碱基团的光致变色螺吡喃化合物的光谱性能和与DNA作用研究

本文合成6种带有席夫碱基团的螺吡喃光致变色化合物,并利用电子吸收光谱、荧光光谱研究了它们的光谱性质以及与DNA的相互作用,考察了不同基团对其作用的影响,对同一化合物研究了在不同pH值、不同离子强度条件下的作用情况,初步探讨了它们与DNA的作用方式.     

直链烷烃近红外光谱的温度效应与应用研究

近红外光谱的温度效应已得到关注,在结构分析和定量分析方面得到了尝试.以直链烷烃为例,对烷烃有机体系近红外光谱的温度效应进行了研究.采集了20~60℃范围内五种直链烷烃(正己烷到正癸烷)及其混合物的近红外光谱并进行了对比分析,仅发现某些谱峰的强度随温度发生微小变化.采用交替三线性分解算法对光谱数据进行了解析,考察了光谱的特征以及随温度和结构的变化.结果表明,链端C₂H₅和链中CH₂基团的光谱受温度的影响不同,但其光谱信号的强度与温度之间都具有良好的线性关系,可根据光谱预测体系的温度;两种基团的光谱信号强度与烷烃分子的碳数或两种基团在分子中相对含量都具有良好的线性关系,可用于直链烷烃混合物组成的估算.     

自组装膜中原位光反应固定化脱氧核糖核酸及膜稳定性

通过静电沉积的方法构筑了含有脱氧核糖核酸(DNA)和重氮树脂(DAR)的交替多层膜.在紫外光照射下,这种静电沉积多层膜相邻层间DNA上的磷酸基团与DAR上的重氮基团发生反应,从而将DNA共价连接到多层膜中.利用紫外-可见吸收光谱和掠角反射吸收傅里叶变换红外光谱(GRAFTIR)研究了这种相邻层间的光化学变化.刻蚀实验结果发现,与光照前相比,光照后的膜在盐溶液中的稳定性大大增强.     

磷脂酰胆碱与牛血清白蛋白相互作用的FT-IR研究

利用傅立叶变换红外(FT-IR)和拉曼(FT-Raman)光谱研究了高浓度磷脂酰胆碱(PC)与牛血清白蛋白(BSA)的相互作用,及Eu3＋对该作用的影响.FT-IR结果显示,PC/BSA混合体系中二者的相互作用主要发生在PC头部极性基团,且这一作用随BSA含量的增加而增强,作用后蛋白质二级结构中α螺旋的比例有所增加. FT-Raman光谱说明PC与BSA的相互作用影响磷脂CH链的排列有序程度. PC/BSA/Eu3＋体系的红外光谱显示, Eu3＋与PC的磷氧键发生了强相互作用,并使蛋白α螺旋的比例进一步增加.     

中位-四(4-N-氰甲基吡啶)卟啉-铜(Ⅱ)络合物及其与脱氧核糖核酸的复合物的表面增强喇曼光谱研究

本文在银胶活性基质上获得了Cu(Ⅰ)的中位-四(4-N-氰甲基吡啶)卟啉络合物Cu(Ⅰ)NACN的表面增强喇曼光谱(SERS)光谱,并与其RRS光谱作了比较,讨论了pH值和Cu(Ⅰ)NACN的浓度对其SERS光谱的影响,研究了小牛胸腺双链DNA及其变性DNA与Cu(I)NACN的复合物的SERS光谱,指出Cu(Ⅰ)NACN是通过吡啶氮和卟啉核共同与银胶作用的,Cu(Ⅰ)NACN是斜向吸附在银表面上的,最佳pH范围在5～6,最佳浓度在大约10～5mol/L;双链DNA和变性DNA的加入不能改变Cu(Ⅰ)NACN在银胶表面上的斜向吸附,在银胶体系中双链DNA的磷酸根通过静电力与Cu(Ⅰ)NACN起弱相互作用,Cu(Ⅰ)NACN可能部分插入变性DNA单链并与之存在同双链DNA一样的静电作用.     

全反式维甲酸合钇(Ⅲ)配合物对DNA的切割和键合作用(英)

以紫外光谱、荧光光谱、粘度法和凝胶电泳方法研究了全反式维甲酸合钇(Ⅲ)配合物与DNA的作用。结果表明，该配合物能在生理条件下比配体和金属离子更有效地切割质粒DNA，体系离子强度和pH值的变化对配合物的切割活性有较大影响，自由基捕捉剂的加入不影响配合物的切割活性。该配合物对DNA的切割可能通过水解机理进行。该配合物可使DNA的粘度增加，使EB-DNA体系的荧光强度和DNA溶液的紫外吸收强度降低。据此推断，该配合物主要以嵌入方式与DNA作用。     

不同催化剂作用下聚乳酸/聚碳酸亚丙酯的酯交换反应

选用辛酸亚锡[Sn(Oct)₂]和钛酸四丁酯(TBT)作为聚乳酸(PLA)/聚碳酸亚丙酯(PPC)的酯交换反应催化剂, 研究了溶液条件下单一催化剂及复合催化剂对PLA/PPC酯交换反应的催化作用. 通过对反应产物的分子结构、 热力学及流变学行为进行分析, 结果发现, 无论在单一催化剂还是复合催化剂作用下, PLA与PPC分子间均发生了酯交换反应, 同时伴随着断链反应. 其中, 当Sn(Oct)₂作为单一催化剂或Sn(Oct)₂/TBT作为复合催化剂时, 样品更倾向发生断链反应而非显著的酯交换反应. 进一步分析纯样品在催化剂Sn(Oct)₂或TBT作用下的反应情况, 结果发现, PPC在反应最初阶段以高分子量的分子链断链为主, 且会发生明显的解拉链降解, 从而导致PLA/PPC在等质量比时酯交换反应程度不高, 这为今后更好地研究PLA/PPC酯交换反应提供了思路.     

A study of the partitioning and sorptive behaviour of butyltins in the aquatic environment

This study was designed to investigate the partitioning and sorptive behaviour of tributyltin(TBT), and its degradation products dibutylitin (DBT) and monobutyltin (MBT), in the aquatic environment. Factorial experiments were undertaken to determine the importance of pH and particulate matter concentration in the sorption of butyltin compounds to solid phases. Results indicate that in freshwaters MBT, and to a lesser extent TBT, will be partitioned towards the particulate phase, whereas DBT exhibits a 50:50 partitioning between particulate and solution phases. In estuarine waters, whilst MBT will almost exclusively sorb on to particulates, TBT will be predominantly in the solid-phase fractions but 10–30% may remain in solution. DBT, in contrast, is solubilized in estuarine waters. A more detailed investigation of TBT sorption and particulate matter concentration was undertaken using adsorption isotherms on different sediment types. The results from batch isotherm tests plotted according to the Freundlich adsorption model revealed that TBT adsorption varied with sediment type, increasing in the order sandy-silt < silty-sand < silty-clay. TBT sorption was found to be reversible, indicating that contaminated sediments may release TBT to overlying waters following sediment distrubance. Interstitial water partitioning studies indicate that TBT predominates in the particulate phase with partition coefficients for TBT higher than for DBT and MBT. The TBT partition coefficient in interstitial waters appears to be related to total organic carbon loadings.     

Organotin concentrations in the Rivers Bure and Yare,Norfolk Broads,England

Butyltin concentrations have been measured at eight freshwater sites (rivers and lakes) in the Norfolk Broads, UK, during 1986 and 1987. Tributyltin (TBT) was found in water samples from seven of the sites. Wherever TBT was present, dibutyltin and (usually) monobutyltin occurred. Levels of TBT exceeded 100 ng dm^?3 in open stretches of both the Rivers Bure and Yare in 1986 and 1987. The highest concentration of TBT recorded for Wroxham Broad (a shallow lake) was 898 ng dm^?3. Values of up to 3.26 μg dm^?3 were measured in water samples taken from a marina. A depth profile for Wroxham Broad showed TBT to be uniformly distributed throughout the shallow water column. The results are discussed in relation to toxicity of TBT to freshwater organisms. Laboratory measurements of the degradation of TBT in freshwater from a marina gave a half-life of six days at 20°C in the light.     

Tandem mass spectrometric sequence characterization of synthetic thymidine-rich oligonucleotides

Tandem mass spectrometry (MS/MS) can provide direct and accurate sequence characterization of synthetic oligonucleotide drugs, including modified oligonucleotides. Multiple factors can affect oligonucleotide MS/MS sequencing, including the intrinsic properties of oligonucleotides (i.e., nucleotide composition and structural modifications) and instrument parameters associated with the ion activation for fragmentation. In this study, MS/MS sequencing of a thymidine (T)-rich and phosphorothioate (PS)-modified DNA oligonucleotide was investigated using two fragmentation techniques: trap-type collision-induced dissociation (“CID”) and beam-type CID also termed as higher-energy collisional dissociation (“HCD”), preceded by a hydrophilic interaction liquid chromatography (HILIC) separation. A low to moderate charge state (−4), which predominated under the optimized HILIC-MS conditions, was selected as the precursor ion for MS/MS analysis. Comparison of the two distinctive ion activation mechanisms on the same precursor demonstrated that HCD was superior to CID in promoting higher sequence coverage and analytical sensitivity in sequence elucidation of T-rich DNA oligonucleotides. Specifically, HCD provided more sequence-defining fragments with higher fragment intensities than CID. Furthermore, the direct comparison between unmodified and PS-modified DNA oligonucleotides demonstrated a loss of MS/MS fragmentation efficiency by PS modification in both CID and HCD approaches, and a resultant reduction in sequence coverage. The deficiency in PS DNA sequence coverage observed with single collision energy HCD, however, was partially recovered by applying HCD with multiple collision energies. Collectively, this work demonstrated that HCD is advantageous to MS/MS sequencing of T-rich PS-modified DNA oligonucleotides.     

Storage stability studies for tributyltin determination in human urine samples using headspace solid‐phase microextraction and gas chromatography mass spectrometry

A headspace solid‐phase micro‐extraction (HS‐SPME) method was employed in order to study the effect of storage conditions of human urine samples spiked with tributyltin (TBT) using gas chromatography and mass spectrometry. To render the analyte more volatile, the derivatization (ethylation) was made in situ by sodium tetraethylborate (NaBEt₄), which was added directly to dilute unpreserved urine samples and in buffers of similar acidity. The stability of TBT in human urine matrix was compared with the stability of TBT in buffer solutions of similar pH value. Critical parameters of storage conditions such as temperature and time, which affect the stability of TBT in this kind of matrix, were examined extensively. The tests showed that the stability of TBT remains practically satisfactory for a maximum of 2 days of storage either at +4 or 20°C. Greater variations were observed in the concentration of TBT in human urine samples at +4°C and lower ones at ?20°C over a month's storage. The freeze–thaw cycles have negative effect on the stability and should be kept to a minimum. The results from spiked urine samples are also discussed in comparison to those acquired from buffer solutions of equal TBT concentration. Copyright © 2012 John Wiley & Sons, Ltd.     

Review: Biodegradation of tributyltins (organotins) by marine bacteria

Many marine bacterial strains have an inherent capability to degrade toxic organotin compounds, especially tributyltins (TBTs), that enter into the environment in the form of insecticides, fungicides and antifouling paints as a result of anthropogenic and industrial activities. Significant degradation of these compounds in the ambient environment may take several years, and it is necessary to consider methods or strategies that can accelerate the degradation process. There have been few demonstrations of biological degradation of these organotin biocides exclusively in laboratory‐scale experiments. Compared with the few bench‐scale degradation processes, there are no reports of field‐scale processes for TBT bioremediation, in spite of its serious environmental threat to non‐target organisms in the aquatic environment. Implementation of field‐scale biodegradation of TBT requires inputs from biology, hydrology, geology, chemistry and civil engineering. A framework is emerging that can be adapted to develop new processes for bioremediation of toxic environmental wastes. In the case of TBT bioremediation, this framework incorporates screening and identification of natural bacterial strains, determination of optimal conditions for growth of isolates and TBT degradation, establishment of new metabolic pathways involved in TBT degradation, identification, localization and cloning of genes involved in degradation and in TBT resistance, development of suitable microbial strains using genetic manipulation techniques for practical applications and optimization of practical engineering processes for bioremediation of organotin‐contaminated sites. The present review mainly addresses the aspect of TBT biodegradation with special reference to environmental sources of TBT, chemical structure and biological activity, resistant and degrading bacterial strains, possible mechanisms of resistance and degradation and the genetic and biochemical basis of TBT degradation and resistance. It also evaluates the feasibility and potential of natural and genetically modified TBT‐degrading bacterial strains in field‐scale experiments to bioremediate TBT‐contaminated marine sites, and makes recommendations for more intensive and focused research in the area of TBT bioremediation mediated by marine bacterial strains. Copyright © 2002 John Wiley & Sons, Ltd.     

Tri‐n‐butyltin binding to a low‐affinity site decreases the F1FO‐ATPase sensitivity to oligomycin in mussel mitochondria

In mussel digestive gland mitochondria the environmental pollutant tri‐n‐butyltin (TBT), other than strongly inhibiting ATPase activity at <1.0 μ m , at ≥1.0 μ m concentration was previously found to desensitize F₁F_O‐ATPase to the antibiotic oligomycin. While F₁F_O‐ATPase inhibition is widely known as one of the main mitochondrial damages caused by TBT, the enzyme's desensitization to oligomycin was quite unexpected. The possible mechanisms involved are here stepwise approached, aiming at enlightening the molecular mechanism(s) of TBT toxicity and the still poorly investigated oligomycin interaction with F_O. The findings strongly suggest that the oligomycin desensitization directly stems from the covalent binding of TBT to monothiols of the F₁F_O‐ATPase. This binding implies sulfur oxidation, irrespective of the possible formation of radical species in mitochondria, a mechanism which does not seem to be involved here. It is hypothesized that TBT interacts with the enzyme complex in at least two sites distinguished by different affinities: TBT binding to the high‐affinity site would lead to ATPase inhibition, while TBT binding to monothiols in the low‐affinity site could mirror the decrease in F₁F_O‐ATPase oligomycin sensitivity at ≥1.0 μ m TBT. Experiments carried out on inside‐out submitochondrial particles hint that TBT binding destabilizes the oligomycin‐blocked F_O conformation, allowing proton flux recovery within F_O, without uncoupling the catalytic function from proton channeling. Copyright © 2012 John Wiley & Sons, Ltd.     

Organometallic complexes with biological molecules. XV. Effects of tributyltin(IV)chloride on enzyme activity,Ca2+, and biomolecule and synthesis in Ciona intestinalis (Urochordata) ovary

Considerable attention has been given in recent years to the possibility that xenobiotics in the environment may affect reproduction in animals. In this study, the relative impact of tributyltin(IV) (TBT) chloride, one of the most toxic environmental pollutants, was investigated using Ciona intestinalis ovary as a model system. The pleiotropic effects of TBT exposure are concentration dependent and include a decrease of ATP levels, lipid content and nucleic acid content and synthesis. In contrast, a marked increase in calcium (Ca²⁺) and glucose content is observed. Furthermore, TBT alters enzymatic activity, inhibiting creatine kinase and stimulating alkaline phosphatase and cholinesterase (at concentrations higher than 10^?5M in sterile sea water solution). The implications of these effects on reproduction and embryonal development are discussed, along with the possibility that they reflect an extreme cellular defence mechanism triggered to avoid deleterious consequences for the survival of the species.Copyright © 2001 John Wiley & Sons, Ltd.     

Preliminary evidence for in vitro methylation of tributyltin in a marine sediment

Recent reports from our laboratory on the occurrence of methylbutyltins in marine sediments and seawater suggest that these compounds are formed in the environment by the methylation of both tributyltin (TBT) and that­of its degradation products, i.e. dibutyltin and monobutyltin, to give Me_nBu_(4?n)Sn for which n = 1, 2 and 3 respectively. We investigated the possibility of inducing methylation of TBT in seawater–sediment mixtures in experiments carried out in vitro using environmental materials collected from a yacht marina in Msida, Malta. Three water–sediment mixtures, which were shown to contain TBT, dibutyltin and monobutyltin but no other organotins, were spiked with tributyltin chloride (90 mg in 100 ml sea‐water/100 ml sediment); to one mixture was added sodium acetate and to another methanol, to act as possible additional carbon sources, and all mixtures were allowed to stand at 25 °C in stoppered clear‐glass bottles in diffused light for a maximum of 315 days. Speciation and quantification of organotins was performed using aqueous phase boroethylation with simultaneous solvent extraction followed by gas chromatography with flame photometric detection. The atmosphere inside the bottles quickly became reducing with abundant presence of H₂S, and after an induction period of about 112 days, and only in the reaction mixture containing methanol, methyltributyltin (MeBu₃Sn) was observed in both sediment (maximum concentration 0.87 µg_Sn g^?1) and overlying water (maximum concentration 6.0 µg_Sn l^?1). The minimum conversion yield of TBT into MeBu₃Sn was estimated to be 0.3%. MeBu₃Sn has a significantly lower affinity for sediment than TBT and, therefore, is more mobile in the marine environment, possibly also migrating into the atmosphere to generate a hitherto unsuspected flux of organotin into that phase. Copyright © 2001 John Wiley & Sons, Ltd.