The promoting effect of organotin compounds upon peroxidation of oleic acid

The effect of the organotin compounds R _nSnCl_4?n (n = 1–3; where R = Me, Et, n‐Bu and Ph) upon oleic ((Z)‐9‐octadecenoic) acid oxidation by dioxygen has been studied at 25, 37, 65, and 95 °C. The promoting effect of organotins upon the formation of oleic acid hydroperoxides is temperature dependent and is at a maximum at a temperature close to the physiological one, but the impact of organotins upon oleic acid peroxidation decreases in the presence of 2,6‐di‐tert‐butylphenol. The role of organic free radicals derived from the Sn? C bond cleavage in the oxidation of oleic acid is discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Fatty acid binding sites of human and bovine albumins: Differences observed by spin probe ESR

Bovine and human serum albumins and recombinant human albumin, all non-covalently complexed with 5- and 16-doxyl stearic acids, were investigated by ESR spectroscopy in solution over a range of pH values (5.5–8.0) and temperatures (25–50 °C), with respect to the allocation and mobility of fatty acid (FA) molecules bound to the proteins and conformation of the binding sites. In all proteins bound FA undergo a permanent intra-albumin migration between the binding sites and inter-domain residence. Nature identity of the recombinant human albumin to its serum-derived analog was observed. However, the binding sites of bovine albumin appeared shorter in length and wider in diameter than those of human albumin. Presumably, less tightly folded domains in bovine albumin allow better penetration of water molecules in the interior of the globule that resulted in higher activation energy of FA dissociation from the binding site. Thus, the sensitive technique based on ESR non-covalent spin labeling allowed quantitative analysis and reliable comparison of the fine features of binding proteins.     

Influence of organotin compounds on phosphatidylserine membranes

Organotin compounds are widely distributed toxicants. They are membrane‐active molecules with broad biological toxicity. We have studied the interaction of tributyltin and triphenyltin with phosphatidylserine model membranes using differential scanning calorimetry, infrared spectroscopy and X‐ray diffraction techniques. Organotin compounds produced a broadening of the gel to the liquid‐crystalline phase transition of the phospholipid and a shifting of the phase transition temperature to lower values. Infrared spectroscopy experiments showed that tributyltin exerted a fluidizing effect on the apolar part of the bilayer, and that both tributyl‐ and triphenyltin interact with the interfacial region of the bilayer, making the carbonyl groups less accessible to water. As seen by X‐ray diffraction experiments, organotin compounds were unable to change the bilayer macroscopic organization of the phospholipid, but they were able to reduce the long‐range order of the multibilayer system and to disorder the packing of the phospholipid molecules. The observed interaction between organotin compounds and phosphatidylserine membranes promotes physical perturbations that could affect membrane function and may mediate some of their toxic effects. Copyright © 2004 John Wiley & Sons, Ltd.     

Nitroxide spin probe study of probe size,hydrogen bonding and polymer matrix rigidity effects on poly(acrylic acid)/poly(ethylene oxide) complexes

An electron spin resonance (ESR) spin probe study was performed on 1 : 1 by weight poly(acrylic acid) (PAA)/poly(ethylene oxide) (PEO) complex over the 100–450 K temperature range with a series of tetramethylpiperidyloxy‐based spin probes. Measurements of the parameters T_5mT, Ta and Td demonstrated the effects of probe size and the strength of hydrogen bonding. The probes in the series Tempone, Tempo, Tempol and Tamine (respectively 4‐oxo‐, unsubstituted, 4‐hydroxy‐ and 4‐amino‐2,2,6,6,‐tetramethylpiperidine ‐1‐oxyl) displayed noticeable increases in the hydrogen‐bonding effect, as indicated by Ta and Td. These increases correlated with increasing hydrogen bond acceptor strength. On the other hand, as the probe size became larger, T_5mT gradually increased due to the free volume decrease. These effects were analyzed using the established theoretical relationship of T_5mT to probe volume expressed by f. Meanwhile, in order to investigate the effect of polymer matrix rigidity, a similar study was performed with a nitroxide spin probe, 2,2,6,6‐tetramethyl‐1‐piperidine‐1‐oxyl (Tempo), on PAA/PEO complexes of different weight compositions. The quantitative fast motion fraction in the composite ESR spectrum was calculated. The influence of changes in the composition of PAA on the molecular mobility was characterized by changes of the spectral parameters and τ_c. The molecular mobility was shown to diminish with increasing content of PAA in PAA/PEO blends duo to the restriction of the polymer matrix rigidity increase. Copyright © 2003 John Wiley & Sons, Ltd.     

Stability of model membranes in the presence of organotin compounds

The influence of tri‐ and di‐alkyltins (TATs and DATs) as well as di‐ and triphenyltin compounds (DPhTs and TPhTs) on haemolysis of red blood cells (RBCs) and stability of planar lipid membranes (PLMs) has been studied. The results obtained show that the efficiency of TATs (trimethyl‐, triethyl‐, tri‐n‐propyl‐ and tributyl‐tin chlorides) in destroying PLMs did not differ greatly when the compounds were studied in solutions of physiological pH (phosphate buffer, pH 7.4). A decrease in pH to 5.0 caused small changes in the efficiency of the three largest TAT molecules and a significant decrease in the efficiency of trimethyltin chloride. Both haemolytic and PLM experiments showed that the most active TAT was tri‐n‐propyltin chloride. The destructive action of DAT (dimethyl‐ and dibutyltin) and DPhT dichlorides was somewhat more differentiated. Dimethyltin dichloride (DMT) interaction with model membranes was a little weaker than that of DPhT and dibutyltin dichlorides and all these compounds influenced the model membranes to a lesser extent than TATs or TPhT. To bring about comparable haemolysis effects the dichlorides had to be used at much greater concentrations than the chlorides. The haemolytic properties of the dichlorides, especially of that of DMT, significantly increased in solution at pH 5.0. TPhT chloride interacted with model membranes similarly to TAT chlorides. Also, no great difference in efficiency of this compound was found for the two buffer solutions used. Copyright © 2000 John Wiley & Sons, Ltd.     

Analytical methods and problems related to the determination of organotin compounds in marine sediments

The determination of organotin compounds in bottom sediments is a complex process that requires a number of analytical steps, i.e. sample collection, transport and storage; extraction of analytes from sediment; derivatization; extract purification; enrichment; and the final chromatographic measurement. The whole process is time and labour consuming, and subject to securing sample representativeness. In this review the most frequently encountered problems and the examples of possible analytical solutions are presented, which encompass the specific steps of speciation analysis of these toxic compounds.     

ESR study of the photolysis of C60Cl6

The photolysis of C₆₀Cl₆ in the presence of α-phenyl-N-tert-butylnitron (PBN) as a spin trap was studied by ESR spectroscopy. It was shown that a C−Cl bond undergoes homolytic cleavage to give a stable fullerenyl radical of the cyclopentadienyl type, whose formation was confirmed by quantum-chemical computations. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 752–754, April, 2000.     

Tandem mass spectral studies of the fragmentation pathways of organotin compounds of general formula R3SnR′

Positive ion‐electron impact (EI) mass spectra of organotin compounds of the type R₃SnR′, where R = Ph, n−Bu, n−Pe and R′ = allyl, vinyl, H and Ph, have been recorded. The spectra were also examined by tandem mass spectrometry (MS‐MS) in order to establish fragmentation reaction mechanisms for compounds bearing mixed substituents. Fragmentation patterns of six organotin compounds, based on precursor‐product ion relationships are proposed. Significant differences were found in the reaction pathways of organotin compounds with different substituents. This technique has potential to predict the effect of substitution on the mass spectra of organotin compounds. Copyright © 2000 John Wiley & Sons, Ltd.     

Toxicity and the cardiovascular activity of organotin compounds: a review

A comprehensive review on toxicity of organotin compounds including sources of their intake and mode of action, and cardiovascular activity of organotin compounds is presented. Further research to develop novel useful organotin compounds having hypertensive activity needs to be carried out. Copyright © 2008 John Wiley & Sons, Ltd.     

Spectroscopic study of ternary copper(II) complexes on a silica surface

The formation of ternary surface complexes of copper(II) with one or two molecules of 2,2′-bipyridine (bpy) or α-picolinic acid (Hpic), which were obtained after adsorption on the silica surface in different ways, was studied by electronic and ESR spectroscopy. Coordination of the ligands, which were preliminarily adsorbed by copper ions, afforded only 1∶1 ternary surface complexes. In both cases, coordinatively more saturated ternary surface complexes were formed only when Cu(bpy)₂ ²⁺ and Cu(pic)₂ were adsorbed on the SiO₂ surface from solutions. The compositions and structures of the ternary surface complexes containing bipyridine ligands are temperature independent, whereas in the picolinate-containing ternary surface complexes, the coordination spheres of the adsorbed complexes are rearranged as the temperature changes. Presented at the First Moscow Workshop on Highly Organized Catalytic Systems (June 19, 1997). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1765–1771, October, 1997.     

Radical steps in the reactions of organometallic compounds with 2-methyl-2-nitrosopropane: experimental evaluation of the validity of the nitroxyl method for investigations of homolytic reactions of organometallic compounds

Radical adducts formed in the reactions of organometallic compounds of group II-V elements and of some organochromium and organoiron compounds with 2-methyl-2-nitrosopropane and phenyl(tert-butyl)nitrone were studied by ESR. Nitroso compounds and nitrones can be used as selective spin traps for investigations of homolytic reactions involving organometallic compounds.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 916–920, May, 1994.     

Biological chemistry of organotin compounds: Interactions and dealkylation by dithiols

In this paper, we review our past and current efforts toward the elucidation of the biological chemistry of organotin compounds. In particular, we cover two prominent aspects of organotin compounds: their reactivity toward biological dithiols, and their degradation (or metabolization) mechanism using a combination of experimental and computational techniques.     

ESR study of products of transformation of 3,6-tert-butylpyrocatechol on alumina, zinca, silica, and titania

The formation of semiquinone and phenoxazyl radicals and metallocomplexes with semiquinone ligands was observed by ESR during the interaction of di-tert-butylpyrocatechol with Al₂O₃, ZnO, SiO₂, and TiO₂. In the case of different modifications of SiO₂, admixtures of TiO₂ exhibit a higher reactivity in complex formation with the organic substrate. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1975–1978, October, 1998.     

Melt polymerization of hexachlorocyclotriphosphazene in the presence of organotin (IV) compounds

The melt polymerization of hexachlorocyclotriphosphazene to poly(dichlorophosphazene) has been studied in the presence of organotin (IV) compounds. Unlike other typical Lewis acids, diethyltin (IV) chloride, Et₂SnCl₂, has shown to be an inhibitor for the thermal polymerization of the trimer, raising the activation energy to 70 kcal/mol. Diethyltin(IV) chloride remarkably delayed the rate of polymerization and efficiently inhibited the crosslinking reaction, thus leading to an improvement in the yield of the linear polymer without sacrifice to its molecular weight. © 1993 John Wiley & Sons, Inc.     

Structural aspects in self-assembled systems of polyoxyethylene surfactants, as studied by the spin probe technique

Typical examples of structural characterization of self-assembled systems by the spin probes technique, selected from our representative results accumulated in the last years of systematic studies, are presented. The choice of the examples has aimed at emphasizing the potentiality of this technique in the study of self-assembled systems, in general, and of those of PEO surfactants, in particular. By using specific ESR parameters (the nitrogen hyperfine splitting (hfs), a_N, the rotational correlation time, τ_c, the order parameter, S) of a variety of properly chosen nitroxides, problems such hydration degree and profile of the PEO chains, ordering and order profile along these chains, their penetrability by the oil solvent, role of the terminal OH in the micellization, as well as differences in these quantities vs. the nature of the aggregate (micelle, reverse micelle, lamellar phase, etc.), nature of the surfactants (conventional or triblock copolymer), solubilizates (water in reverse micelles or various alcohols in micelles) and temperature have been discussed.     

顶空固相微萃取-气相色谱-质谱法测定玩具中可迁移有机锡化合物

建立了顶空固相微萃取结合气相色谱-质谱联用技术测定玩具中10种可迁移有机锡化合物的方法。玩具材料经0.07 mol/L HCl浸泡2 h后,使用醋酸-醋酸钠缓冲溶液将浸泡液的pH值调至4.7,然后加入四乙基硼化钠将浸泡液中的有机锡化合物乙基化,在振荡条件下用100 μ m聚二甲基硅氧烷(PDMS)纤维进行顶空固相微萃取,萃取完成后将纤维插入气相色谱进样口进行热解吸,使用DB-5毛细管柱对10种有机锡化合物进行分离。10种有机锡化合物的检出限为0.5~5 μg/kg。两个加标水平(0.500 μg/L和5.00 μg/L)下的回收率分别为80.7%~118.7%和86.2%~120.5%,RSD均低于15%。应用该方法测定了玩具可触及材料(包括涂层、织物、塑料、木料)中的可迁移有机锡化合物。该方法简便、快速、灵敏度高,不需使用有毒有机溶剂,绿色环保。     

Kinetics of the dehydration of 2-propanol on modified activated charcoal containing acid sites

A study was carried out on the kinetics of the dehydration of 2-propanol on activated bone charcoal (ABC) with supported acid sites. The rate-limiting step is the loss of water from the alcohol molecule adsorbed on the acid site. The sites containing the minimum amount of water are the most active. The reaction on these sites presumably proceeds through a concerted mechanism, which is possible at sufficiently high temperatures (above 120 °C). Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 321–327, September–October, 2008.     

ESR spectroscopic investigation of steric and polar factors in the addition of radicals to unsaturated compounds

The rate constants of the addition of CCl₃CH₂ClCH₃(R⁶) radicals to -methyl-styrene, styrene, methyl methacrylate, methyl acrylate, and acrylonitrile and of CCl₃CH₂(CH₃)₂(R⁷) radicals to styrene, methyl acrylate, and acrylonitrile were determined by ESR spectroscopy. It was shown that the radicals R⁶ and R⁷ possess approximately equal reactivity in addition to unsaturated compounds, despite the difference in the donor-acceptor properties of the substituents at the vinyl group. In a comparison of the reactivity of radicals R⁶ and R⁷ with the reactivity of radicals CCl₃CH₂H₂(R¹), CCl₃CH₂HCH₃(R³), CCl₃CH₂HCl(R⁴), and ClCH₂CH₂Cl₂(R⁵) [1] in addition reactions, it was shown that polar and steric effects of the substituents situated in the -position to the radical site of the above-mentioned radicals, as well as the donor-acceptor properties of the substituents at the vinyl group in the unsaturated compounds, lead to appreciable changes in reactivity.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 136–141, January, 1992.     

Speciation of organotin compounds in water and sediments by gas chromatography/atomic absorption spectrometry (GC-AAS)

A commercially available atomic absorption detector coupled to a wide-bore column-containing gas Chromatograph (GC-AAS) was utilized to detect organotin compounds. Speciation was performed by pentane extraction of the organotin species as the corresponding sodium diethyldithiocarbamate complexes, enrichment by rotary evaporation, derivatization with Grignard reagent and finally the extracted water and sediment samples were separated and detected on the GC-AAS system.