The effect of some phenyltin compounds on the thermotropic phase behaviour and the structure of model membranes

The effects of diphenyltin dichloride (DPhT), triphenyltin chloride (TPhT) and tetraphenyltin (TTPhT) on the thermotropic phase behaviour of phosphatidylcholine bilayers were studied. All the phenyltin compounds investigated affected phase transitions differently. TTPhT broadened the main phase transition but it left the transition temperatures and enthalpy unchanged. TPhT reduced the transition temperatures and the enthalpies while DPhT showed a dual effect on the pretransition and the main transition. At low concentrations DPhT reduced the temperatures of the transitions slightly and at higher concentrations it increased them. Based on differential scanning calorimetry (DSC) and also ¹H NMR and ³¹P NMR measurements, it is suggested that DPhT induces interdigitated gel phase formation and TPhT induces hexagonal phase formation. TTPhT seems to affect the structure only a little. The toxic activity of DPhT and TPhT seems to be connected with their ability to induce changes in the membrane structure. Copyright © 2000 John Wiley & Sons, Ltd.     

The effect of phenyltin chlorides on osmotically induced erythrocyte haemolysis

The toxicity of many amphiphilic compounds may result from their effect on the lipid phase of biological membranes. Upon incorporation such compounds may change the properties of membranes in general and in particular alter the organization of membrane lipids. These changes should affect, among other things, the mechanical properties of membranes. We selected two amphiphilic compounds, diphenyltin dichloride (Ph₂SnCl₂) and triphenyltin chloride (Ph₃SnCl), which are known to be located at different regions of the lipid bilayer and to be toxic. As a model biological membrane the erythrocyte plasma membrane was used. Analysis of the haemolysis kinetics showed differences between the effect of the compound studied on mechanical properties at so‐called non‐lytic concentrations. Diphenyltin dichloride showed a limited effect on erythrocyte haemolysis, whereas triphenyltin chloride affected all the parameters measured (extent of initial haemolysis, extent of final haemolysis and membrane mechanical strength). We correlated these effects with the location of the investigated compounds in liposomes. The presented data show that triphenyltin chloride reduces the erythrocyte plasma membrane mechanical strength and increases the extent of haemolysis under osmotic stress conditions. Copyright © 2005 John Wiley & Sons, Ltd.     

Di‐ and tri‐phenyltin chlorides transfer across a model lipid bilayer

A compound's ability to penetrate the plasma membrane of a cell is the critical parameter that determines its potential to become a biologically potent factor. A well‐known group of organotin compounds that exhibit toxic properties in relation to biological systems are phenyltins. There are as yet no studies that in a direct manner have established whether organotin compounds such as diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT) diffuse, or not, through the lipid bilayer, although we know that at least some organotins absorb in both liposome and biological membranes. In this paper we present a series of experiments that show transfer of these compounds across the lipid membrane using the stopped‐flow technique. The results obtained demonstrate that DPhT and TPhT first adsorb onto the lipid bilayer surface, in a diffusion‐controlled manner and within a very short time (0.05 s), whereas the membrane crossing was observed to be on the order of a minute. The adsorption process was easily fitted with a single exponential for both the compounds studied, indicating a single process phenomenon. The longer time kinetics (characteristic of membrane crossing) showed a complex dependence on compound concentration and the presence of cholesterol in the membrane. On passing from the outer to the inner surface of the bilayer, organotins undergo desorption and enter the liposome interior, which has been shown in lipid monolayer desorption studies. In conclusion, it can be stated that amphiphilic DPhT and TPhT permeate the liposome membrane. Copyright © 2005 John Wiley & Sons, Ltd.     

Thermolysis of the phenyltin chlorides,PhxSnCl4–x, (x=1−3): Products and pathways

The thermal degradation of triphenyltin chloride, diphenyltin dichloride and phenyltin trichloride has been studied by pyrolysis at 375°C in sealed tubes for various time periods. In all cases, biphenyl and tin(II) chloride are produced. For both phenyltin trichloride and diphenyltin dichloride, ter- and poly-phenyls are also obtained. In some cases tin(IV) chloride or elemental tin are obtained. Pathways that account for all observed products are presented.     

Acid extraction treatment of sediment samples for organotin speciation; occurrence of butyltin and phenyltin compounds on the cadiz coast,south-west spain

A method is described for leaching of nanogram amounts of mono-, di and tri-butyltin compounds and mono-, di- and tri-phenyltin compounds from sediments. The procedure is based on soaking the sediments in a water–hydrogen bromide mixture (2:3) with magnetic stirring for 1 h followed by extraction with 0.02% (w/v) tropolone solution in pentane for 2 h. Organotins are determined by GF FPD after clean-up through a Florisil column and derivatization by Grignard pentylation. The method has been applied to the study of water and sediments in different areas of south-west Spain. Predominant species are butyltins, especially tributyltin (TBT), which has high values in waters and sediments of Puerto de Santa Maria and Cadiz Bay, as well as in sediments of the Sancti Petri Channel, which suggests a harmful action on biota. A direct relation has been found beween organotin levels and distance of potential focus determined by boating activities. In addition, the relative occurrence of dibutyltin (DBT) and monobutyltin (MBT) together with TBT has been noted, possibly as a result of a degractation process, and the influence of grain size of sediment and presence of organic matter on organotin accumulation has been studied.     

P NMR investigation of a ringing gel phase and adjacent phases

The temperature-surfactant concentration phase diagram was examined for the dodecyltrimethylammonium dimethylphosphate/3-methyl-3-methoxybutanol/water ternary system. The phase diagram contained a highly elastic gel phase which is known as a “ringing gel phase”. The ringing gel phase and adjacent phases in the ternary system were investigated by polarized optical microscopy, freeze-fracture transmission electron microscopy, and ³¹P NMR. Globular textures were observed in an optically isotropic gel phase. Since the globules were larger than those found in an isotropic solution, the texture consists of domains of aggregated units in the cubic (I₁) phase. Structure units of domains are equivalent to microemulsions which are constructed by surfactant molecules and swollen by alcohol in the isotropic (L₁) phase. Characteristic polarized microscopic textures were visualized in two phases with higher surfactant concentrations. These phases were identified as being hexagonal (H₁) and lamellar (L) liquid crystals which was confirmed by transmission electron microscopy. The ³¹P NMR signal of the ringing gel showed a sharp singlet the same as that of the L₁ phase, indicating the fully averaged anisotropic interaction of the aggregates. The characteristic NMR signals of the anisotropic hexagonal and lamellar liquid crystal phases displayed chemical shielding with an asymmetric lineshape.     

Speciation of phenyltin(IV) compounds using high‐performance liquid chromatography. Part 2: The direct analysis of mixed standard solutions of triphenyltin halides/pseudohalide and of triphenyltin carboxylates containing functional group variations in the esteryl moiety

Simultaneous speciation of mixed standard solutions of triphenyltin halides (triphenyltin chloride, bromide, iodide) and pseudohalide (triphenyltin isothiocyanate) has been achieved with reversed‐phase high‐performance liquid chromatography on a Waters Spherisorb S5W ODS‐2 (octadecyl‐silica) column. An isocratic mixture of 95:5 (v/v) acetonitrile:water was used as the mobile phase at a flow rate of 1 ml min^?1. A series of selected triphenyltin carboxylates, Ph₃SnOCOZ, where Z = Me, Ph, CH:CHPh, CH:NOMe, CH₂SC₅H₄N and CH₂SC(S)NMe₂, was also similarly analysed using this system with two separate isocratic elutions using 100% acetonitrile and 96:4 (v/v) acetonitrile:water as the mobile phase. UV detection was done at 254 nm and the total run time for each analysis was less than 3 min. The detection limits for all the phenyltin(IV) compounds were in the range 0.01–0.03 ppm. Spiked water samples containing the triphenyltin carboxylates could also be simultaneously analysed by the above method without the need for any prior derivatization, following extraction with hexane. Pretreatment of the aqueous sample with NaCl/HCl and of the organic phase with hexamethylphosphoramide enabled recoveries of about 80% of the triphenyltins. Copyright © 2002 John Wiley & Sons, Ltd.     

Toxic effect of triphenyltin chloride on the alga Spirulina subsalsa

A previous study on the deleterious effect of triphenyltin chloride (TPTCl) on the alga Spirulina subsalsa reported on four physiological and biochemical indices (or parameters): growth rate, chlorophyll content, phycocyanin content and nitrate reductase activity. In the present study, further research was performed to confirm the findings reported in the previous paper, using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM images show significant changes in the screw‐pitch of S. subsalsa, suggesting that TPTCl may damage the inheritance characteristics of S. subsalsa. The TEM images illustrate that the external pectin theca, limiting membrane and inter photosynthetically active lamella in the S. subsalsa cell are those targets that can be easily damaged. Reversible and irreversible cell damage (cell necrosis) are also observed. Copyright © 2002 John Wiley & Sons, Ltd.     

On the heavy atom on light atom relativistic effect in the NMR shielding constants of phosphine tellurides

The relativistic HALA effect has been shown to depend on the spatial deformation of the lone electron pairs of a heavy atom, as demonstrated for alkyl and alkene phosphine tellurides. It was found that HALA effect on phosphorous nuclear magnetic resonance shielding constant is strongly dependent on the spatial arrangements of light substituents on phosphorus, resulting in the deformation of the lone electron pairs of tellurium.     

The influence of sodium chloride and urea on chromonic liquid crystals formed by CI Acid Red 266

Chromonic liquid crystals are currently receiving renewed interest with particular attention on the Edicol Sunset Yellow (ESY)/water system, which forms columnar nematic and hexagonal phases. CI Acid red 266 is structurally fairly similar to ESY and also forms columnar nematic and hexagonal phases but at much lower concentrations (>1%). In this study, we have examined the influence of sodium chloride and urea on chromonic liquid crystals formed by CI acid red 266. The techniques employed were polarising microscopy, X-ray diffraction and ²H NMR. Sodium chloride moves the concentration at which mesophases form to higher values. Once formed, the mesophases are stable to slightly higher temperatures. Screening of the interstack electrostatic repulsions by added electrolyte appears to be responsible for the changes. Urea can be added in fairly large concentrations (up to 25 wt%) without significant changes in mesophase stability. X-ray diffraction measurements show that there is little change in the aggregate structure with added urea. NMR measurements on urea and water ordering show that urea has much larger order parameters than water. Both order parameters are much smaller than values reported for ESY, but this is simply because of the lower dye concentrations. The larger order parameters for urea appear to arise from some intercalation of urea into the acid red 266 stacks. There is no evidence for changes in ‘water structure’ by the addition of urea.     

^31P NMR Studies on the Ligand Dissociation of Trinuclear Molybde-num Cluster Compounds

A series of carboxylate-substituted trinudear molybdenum dus-ter compounds formulated as Mo3S4(DTP)3(RCO2)(L), where RffiH, CH3, C2H5, CH2Cl, CCl3, R^1C6H4(R^1 is the group on the benzene ring of aromatic carboxylate ), L=pyridine,CH3CN, DMF, have been synthesized by the ligand substitu-tion reaction. The dissociation of the loosely-coordinated ligand L from the cluster core was studied by ^31p NMR. The dissocia-tion process of L is related to the solvent, temperature, and acidity of carboxylate groups, so as to affect the solution struc-ture and reactive properties of the duster. The long-distance in-teraction between ligands RCO2 and L is transported by Mo3S4 core.     

The Synthesis and 31P NMR Spectral Studies of Cyclophosphazenes

A modified method for preparing large-scale quantities of pure hexachlorocyclophosphazene (N₃P₃Cl₆) and octachlorocyclotetraphosphazene (N₄P₄Cl₈), phosphorus pentachloride with ammonium chloride, in the presence of zinc chloride, has been developed. The time of the reaction and the quantities of the catalyst are also studied. It is found that the optimum reaction time is 1.5 h and by-products are remarkably reduced by addition of 10% zinc chloride. As indicated by the ³¹ P NMR spectra, the synthesis and separation of cyclophosphazenes can be accomplished in moderate yield of tetramer (39%) and good yield of trimer (83%).     

NMR studies of the conformational effect of single and double 3'-S-phosphorothiolate substitutions within deoxythymidine trinucleotides

NMR spectroscopy has been used to investigate the conformational effects of single and two consecutive 3'-S-phosphorothiolate modifications within a deoxythymidine trinucleotide. The presence of a single 3'-phosphorothioate modification shifts the conformation of the sugar ring it is attached to, from a mainly south to north pucker; this effect is also transmitted to the 3'-neighbour deoxyribose. This transmission is thought to be caused by favourable stacking of the heterocyclic bases. Similar observations have been made previously by this group. When two adjacent modifications are present, the conformations of the attached deoxyribose rings are again shifted almost completely to the north, however, there is no transmission to the 3' deoxyribose ring. Base proton chemical shift analysis and molecular modelling have been used to aid elucidation of the origin of this feature. The observation for the dimodified sequence is consistent with our previously reported results for a related system in which spaced modifications are more thermodynamically stable than consecutive ones.     

A Nd-carboxylate catalyst for the polymerization of 1,3-butadiene: The effect of alkylaluminums and alkylaluminum chlorides

The ternary neodymium-based catalyst for the polymerization of 1,3-butadiene, Nd(versatate)₃/Ali-Bu₂H/tert-butyl chloride, has been examined with respect to the effects of a range of alkylaluminums and alkylaluminum chlorides. Using either pre-formed or in situ catalysts, observations pertaining to catalyst activity and physical state and the characteristics of the final polymer are discussed. The catalyst activity series with the type of alkylaluminum was found to be: Aln-Pr₃ ? Aln-Dodec₃ = Aln-Oct₃ = Aln-Hex₃ > Ali-Bu₂H > Ali-Bu₃ > AlEt₃ ? AIMe₃. Polybutadiene cis content was found to vary with the type of alkylaluminum used. Pre-formed catalysts using methylaluminum chlorides as chloride source were found to be the most active; AlMe₂Cl chloride gave the highest activity. The activity of in situ catalysts prepared using alkylaluminum chlorides was found to be independent of alkylaluminum chloride structure. Polybutadiene prepared using catalysts based on different alkylaluminums and alkylaluminum chlorides was found to decrease in cis content with conversion. © 1995 John Wiley & Sons, Inc.     

Tungsten‐183 NMR study of cis‐[W(CO)4(PPh3)(4‐RC5H4N)]; effect of varying the σ donor strength of the pyridine

Tungsten‐183 NMR data are reported for the complexes cis‐[W(CO)₄(PPh₃)(4‐RC₅H₄N)] (R = H, Me, Ph, COMe, COPh, OMe, NMe₂, Cl, NO₂). The ¹⁸³W chemical shift (obtained by indirect detection using ³¹P) is found to correlate with the Hammett σ function for the group R, with ¹⁸³W shielding increasing approximately linearly with the donor strength of the pyridine over a range of 93 ppm. The X‐ray structures of cis‐[W(CO)₄(PPh₃)(4‐MeOC₅H₄N)] and cis‐[W(CO)₄(PPh₃)(4‐PhCOC₅H₄N)] are also reported. Copyright © 2013 John Wiley & Sons, Ltd.     

The effect of the detergent cetyltrimethylammoniumchloride on the phase behaviour of dipalmitoylphosphatidylcholine: A high precision calorimetric study.

The influence of the linear, positively charged detergent cetyltrimethylammoniumchloride (CTAC1) on the well known phase behaviour of fully hydrated dipalmitoylphosphatidylcholine (DPPC) has been studied along fourteen isopleths of the phase diagram using high sensitivity scanning microcalorimetry. Particular interest was focused towards the effects of very small amounts of detergent down to the region of 1 CTAC1 per 10⁴ DPPC-molecules.Even starting with such low concentrations distinct changes of the thermograms are detectable by high sensitivity DSC. Essentially, the phase diagram is cut into four domains between the two limiting cases of pure phospholipid multilamellar dispersion and isotropic solution of detergent micelles, respectively. At the present stage these four regions in the phase diagram are identified as follows : 1. 0–1 Mol % CTAC1: a modified lamellar phase 2. 1–50 Mol % CTAC1: a two-phase region with this modified lamellar phase coexisting with a newly formed detergent-rich phase. 3. 50–90 Mol % CTAC1: large mixed micelles. 4. > 90 Mol % CTAC1: an isotropic solution of small mixed phospholipid/detergent micelles.     

Solid‐state 31P NMR investigation on the status of guanine nucleotides in paclitaxel‐stabilized microtubules

Microtubule dynamics is a target for many chemotherapeutic drugs. In order to understand the biochemical effects of paclitaxel on the GTPase activity of tubulin, the status of guanine nucleotides in microtubules was investigated by ³¹P cross‐polarization magic angle spinning (CPMAS) NMR. Microtubules were freshly prepared in vitro in the presence of paclitaxel and then lyophilized in sucrose buffer for solid‐state NMR experiments. A ³¹P CPMAS NMR spectrum with the SNR of 25 was successfully acquired from the lyophilized microtubule sample. The broadness of the ³¹P spectral lines in the spectrum indicates that the molecular environments around the guanine nucleotides inside tubulin may not be as crystalline as reported by many diffraction studies. Deconvolution of the spectrum into four spectral components was carried out in comparison with the ³¹P NMR spectra obtained from five control samples. The spectral analysis suggested that about 13% of the nucleotides were present as GTP and 37% as GDP in the β‐tubulin (E‐site) of the microtubules. It was found that most of the GDPs were present as GDP‐P_i complex in the microtubules, which seems to be one of the effects of paclitaxel binding. Copyright © 2015 John Wiley & Sons, Ltd.     

水杨酸与二烷基亚磷酸酯反应历程31P NMR与电喷雾质谱跟踪研究

The reaction between salicylic acid and dialkyl phosphite was traced by electrospray ionization mass spectrometry and ^31P NMR. All reactants, unstable intermediates and products were detected. The mechanism was proposed based on ESI-MS results and ^31P NMR profiles.     

2-乙酰基-5-甲基-1,2,3-二氮磷杂环戊二烯同丙炔醇反应研究

用付里叶变换红外光谱及³¹PNMR,探索了2-乙酰基-5-甲基-1,2,3-二氮磷杂环戊二烯同丙炔醇的动态反应过程,推测了可能的反应机理,并通过对二配位磷化物对应的三配位磷化物(2-乙酰基-3-氯-5-甲基-1,2,3-二氮磷杂环戊烯)同丙炔醇反应的研究,验证了二配位磷化物反应机理的可能性。