Low Molecular Weight Intermediates Research Articles

Advancing Anticancer Drug Discovery: Leveraging Metabolomics and Machine Learning for Mode of Action Prediction by Pattern Recognition.

A bottleneck in the development of new anti-cancer drugs is the recognition of their mode of action (MoA). Metabolomics combined with machine learning allowed to predict MoAs of novel anti-proliferative drug candidates, focusing on human prostate cancer cells (PC-3). As proof of concept, 38 drugs are studied with known effects on 16 key processes of cancer metabolism, profiling low molecular weight intermediates of the central carbon and cellular energy metabolism (CCEM) by LC-MS/MS. These metabolic patterns unveiled distinct MoAs, enabling accurate MoA predictions for novel agents by machine learning. The transferability of MoA predictions based on PC-3 cell treatments is validated with two other cancer cell models, i.e., breast cancer and Ewing's sarcoma, and show that correct MoA predictions for alternative cancer cells are possible, but still at some expense of prediction quality. Furthermore, metabolic profiles of treated cells yield insights into intracellular processes, exemplified for drugs inducing different types of mitochondrial dysfunction. Specifically, it is predicted that pentacyclic triterpenes inhibit oxidative phosphorylation and affect phospholipid biosynthesis, as confirmed by respiration parameters, lipidomics, and molecular docking. Using biochemical insights from individual drug treatments, this approach offers new opportunities, including the optimization of combinatorial drug applications.

Cationic and anionic cross-assisted synergistic photocatalytic removal of binary organic dye mixture using Ni-doped perovskite oxide

Organic dyes present in industrial wastewater are the major contributor to water pollution, which harm human health and the environment. Photocatalytic dye degradation is an effective strategy for water remediation by converting these organic dyes waste into non-harmful by-products. Therefore, in this study, Ni-doped LaFeO3 (NLFO) perovskite nanoparticles were extensively explored for photocatalytic degradation of cationic and anionic dyes and their mixture. The NLFO nanoparticles were successfully synthesized by surfactant assisted hydrothermal method under controlled Ni doping. The X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) revealed the variation in size (40–70 nm) of orthorhombic crystalline LFO nanoparticles with Ni doping and hence the size of microspheres (0.78. to 1.78 μm). The kinetic studies revealed that the LaFe0·6Ni0·4O3 performed well by providing degradation efficiency of 99.2% in 210 min, 99.1% in 100 min, and 98.4% in 70 min for Crystal Violet (CV), Congo Red (CR), and their mixture with rate constant of 0.019, 0.039, and 0.055 min−1 respectively. The radical scavenger tests indicated the synergetic contributions of O2− and •OH− active radicals in faster degradation of CV and CR dye mixture. The stepwise fragmentation of dye molecule during the photocatalytic degradation identified from the LCMS indicates the degradation of CV dye through de-alkylation and benzene ring breaking, whereas azo bond cleavage and oxidation lead to low molecular weight intermediates for CR dye, which all together helped to degrade their dye mixture (50 mg L−1 and 100 mg L−1) in significantly lesser time (70 min). Overall, the Ni-doped LFO microsphere consisting of nanoparticles acts as a superior catalyst for the more efficient and faster degradation of binary dye mixture.

Iron nanoparticles supported on N-doped carbon foam with honeycomb microstructure: An efficient potassium peroxymonosulfate activator for the degradation of fluoranthene in water and soil

A promising technology was developed for the remediation of fluoranthene (FLT) contaminated water and soil. Specifically, iron nanoparticles supported on N-doped carbon foam (Fe@CF-N) was synthesized by in-situ impregnation and a unique calcination process using pine cone as the precursor. The obtained Fe@CF-N was used as an activator of potassium peroxymonosulfate (PMS) to degrade FLT in water and soil. According to experimental results, Fe@CF-N had a three-dimensional network structure with a large specific surface area of 249.0 m2 g−1, displaying excellent catalytic performance. The maximum removal efficiency of FLT in water and soil reached 81.83% and 78.12% within 180 min, respectively. After four consecutive degradation cycles, the removal efficiency of FLT in water was still 55%. Electron spin resonance (ESR) measurements showed that hydroxyl radicals (·OH), sulfate radical (SO4−·) and 1O2 were the major reactive oxygen species (ROS). A series of low molecular weight intermediates were generated during the FLT degradation progress, such as C6H6O3 and C3H8O2. The effect of Fe@CF-N/PMS system on the phytotoxicity was evaluated via bioassay based on peas. The results indicated that seed germination rate and root shoot elongation of remediated soil by Fe@CF-N/PMS system were not significantly different from those of noncontaminated soil. This study provided a cost-effective remediation option for PAHs contaminated water and soil.

Improving the degradation of benzo[a]pyrene and soil biodegradability by enhanced ozonation with mechanical agitation

Gas-phase ozone (O3) can easily diffuse into soil aggregates and effectively degrade hydrocarbon compounds. However, gas channels in soil impede remediation efficiency. This study developed an enhanced ozonation by applying mechanical agitation (100 and 150 rpm) compared with conventional ozonation (0 rpm), to improve degradation of benzo[a]pyrene (BaP) and soil biodegradability. During ozonation process, O3 consumption, BaP removal, soil carbon balance, and intermediates of BaP were investigated. Results showed that the enhanced ozonation disturbed gas channels and improved utilization of O3. At 90 min, more than 90% of the initial BaP (67.86 mg/kg) was degraded at 100 rpm, while it was 83.61% at conventional ozonation. Enhanced ozonation rapidly oxidized soil organic carbon (SOC), Acetone-n-hexane-extractable organic carbon (AeOC), residual organic carbon (ROC) and BaP into dissolved organic carbon (DOC), which increase of DOC was 31.97% higher than conventional ozonation. Enhanced ozonation accelerated decomposition of BaP to more biodegradable and lower molecular weight intermediates at short time mainly by increasing direct ozonation, which was conducive to the subsequent biodegradation. This work provides an enhanced ozonation to improve the degradation efficiency of BaP in soil by destroying gas channels and enhancing the utilization efficiency of O3 and direct ozonation.

Sugar sources as Co-substrates promoting the degradation of refractory dye: A comparative study

Four sugar sources were used as co-substrates to promote the degradation of a selected refractory dye reactive black 5 (RB5) by the natural bacterial flora DDMZ1. The boosting performance of the four sugar sources on RB5 decolorization ranked as: fructose > sucrose > glucose > glucose + fructose. Kinetic results of these four co-metabolism systems agreed well with a first-order kinetic model. Four sugar sources stimulated the extracellular azoreductase secretion causing enhanced enzyme activity. An increased formation of low molecular weight intermediates was caused by the addition of sugar sources. The toxicity of RB5 degradation products was significantly reduced in the presence of sugar sources. The bacterial community structure differed remarkably as a result of sugar sources addition. For a fructose addition, a considerably enriched population of the functional species Burkholderia-Paraburkholderia and Klebsiella was noted. The results enlarge our knowledge of the microkinetic and microbiological mechanisms of co-metabolic degradation of refractory pollutants.

Effective degradation of primary color direct azo dyes using Fe0 aggregates-activated persulfate process

The present study examined the oxidation power of a Fe0 aggregates/persulfate (PS/Fe0) system for the degradation of the wastewater containing mixed primary direct dyes (i.e., Sirius® Gelb S-2G, Sirius® Red F3B, and Sirius® Turkis GL01). Results indicated that decolorization efficiency was determined by operating parameters of the PS/Fe0 system and the structural complexity of dye molecules. System efficiency increased with increasing persulfate and Fe0 dosages. Faster decolorization was observed in experiments conducted at pH < 10. The process obeyed a first-order kinetics. Slow heterogeneous reactions were observed at high initial pH (>10.5) and low PS concentration (<2 × 10−3 M). Inhibitory effect occurred in systems containing salts Na2SO4, NaCl, Na2CO3, and Na2HPO4 at 1 × 10−2 M. The effect was suppressed when reaction temperature was raised to 55 °C. Heat enhanced not only decolorization efficiency, but also COD removal. Complete decolorization of a mixed dye containing ADMI (the American Dye Manufacture Institute) 15105 was achieved within10 min in the PS/Fe0/55 °C system with an initial pH of 6.0 and dosages of 5 × 10−3 M Na2S2O8 and 0.5 g/L Fe0. Low molecular weight intermediates including organic acids were identified. Due to a relatively low activation energy (4.68 kcaL/mol), the PS/Fe0 system exhibited higher efficiency at higher temperature. This study demonstrated that Fe0-activated PS is a promising process for the treatment of textile wastewaters containing mixed azo direct dyes.

Differential Degradation and Detoxification of an Aromatic Pollutant by Two Different Peroxidases.

Enzymatic degradation of organic pollutants is a new and promising remediation approach. Peroxidases are one of the most commonly used classes of enzymes to degrade organic pollutants. However, it is generally assumed that all peroxidases behave similarly and produce similar degradation products. In this study, we conducted detailed studies of the degradation of a model aromatic pollutant, Sulforhodamine B dye (SRB dye), using two peroxidases—soybean peroxidase (SBP) and chloroperoxidase (CPO). Our results show that these two related enzymes had different optimum conditions (pH, temperature, H2O2 concentration, etc.) for efficiently degrading SRB dye. High-performance liquid chromatography and liquid chromatography –mass spectrometry analyses confirmed that both SBP and CPO transformed the SRB dye into low molecular weight intermediates. While most of the intermediates produced by the two enzymes were the same, the CPO treatment produced at least one different intermediate. Furthermore, toxicological evaluation using lettuce (Lactuca sativa) seeds demonstrated that the SBP-based treatment was able to eliminate the phytotoxicity of SRB dye, but the CPO-based treatment did not. Our results show, for the first time, that while both of these related enzymes can be used to efficiently degrade organic pollutants, they have different optimum reaction conditions and may not be equally efficient in detoxification of organic pollutants.

Exploring the diverse potentials of Planococcus sp. TRC1 for the deconstruction of recalcitrant kraft lignin

Kraft lignin (KL) is the chief contaminant which is responsible for dark coloration, toxicity and high chemical oxygen demand (COD) of paper pulp mill effluent. The present study investigated the diverse potentials of Planococcus sp. TRC1 in the biodegradation of KL. Preliminary evaluation indicated that the strain was able to grow on broad spectrum of lignin-derived compounds, decolorize lignin-mimicking dyes and catabolize substrates of ligninolytic enzymes. Response surface methodology (RSM) was executed to perform the optimization of different process parameters. The results displayed that Planococcus sp. TRC1 could completely utilize 100 mg L−1 of KL and 78% of 200 mg L−1 of KL as sole source of carbon with concurrent reduction in COD and color. The biokinetic details of KL biodegradation showed that the values of $$\mu^{*}$$ , µ max, $$q^{*}$$ and q max were 0.018 h−1, 0.01 h−1, 0.023 g g−1 h−1 and 0.05 g g−1 h−1, respectively. UV–visible spectrophotometry, SEM and FTIR indicated the significant alterations in the surface morphology, functional groups and chromophores during the course of biodegradation. XRD revealed the emergence of peak signifying the formation of low molecular weight intermediates after bacterial treatment. Considering the environmental impact, bacterial-treated KL illustrated less phytotoxicity using Vigna radiata seed bioassay. These results suggested that Planococcus sp. TRC1 could be a promising strain for the degradation of KL in an ecofriendly way.

Degradation Mechanism of Methylene Blue in a Heterogeneous Fenton-like Reaction Catalyzed by Ferrocene

Ferrocene (Fc) was used to catalyze a heterogeneous Fenton reaction for the degradation of methylene blue (MB). The high catalytic activity and stability of Fc in the Fc/Fenton-like system are confirmed. MB removal percentage could still maintain at 99.50% after Fc was successively used for three cycles and only 1.12% of Fc dissolved with 100% discoloration of MB, indicating the good reusability and stability of Fc. The reaction rate can be accelerated by improving the dosage of the catalyst and the temperature, and the degradation of MB was found to follow the pseudo-first-order kinetic model and the activated reaction energy was calculated to be 82.71 kJ/mol. MB was determined to be degraded through three different pathways simultaneously during the Fc/Fenton-like process, forming Cl–, NO3–, SO42–, and lower molecular weight intermediates: C–N and C–S broke to form the previous rarely reported benzothiazole (determined by liquid chromatography–mass spectrometry), C–N broke to form phenol, and -OH and -HSO3 connected to MB.

Degradation and kinetics of H2O2 assisted photochemical oxidation of Remazol Turquoise Blue

Advanced Oxidation Processes based degradation of organic pollutants along with enzymatic approaches have gained prominence lately for efficient means of remediation of polluted wastewater. In the present study the photolytic oxidation of a model organic pollutant namely Remazol Turquoise Blue (RTB) dye, using H2O2 and UV light is reported. The photolytic degradation of RTB obeyed first order kinetics for which apparent rate constants could be calculated. Various parameters that could affect RTB degradation such as RTB concentration, pH, H2O2 dose and irradiation time were also studied to come up with optimized degradation conditions. Under optimum operating conditions, 50% decoloration of the dye could be achieved in 10min. In addition, the effect of various ions on RTB degradation was also studied and showed that PO43-,Cl-, and CO32- ions increased the % degradation of this dye, which were most likely due to increased generation of OH radicals by subsequent reactions of these anions in solution. Interestingly, addition of redox active metals like Fe3+, Cd2+, Ni2+ and Zn2+ all led to decrease in the % dye decoloration and this effect was explained on the basis of their reactions with hydroxyl radicals. To confirm the actual breakdown of RTB, LC–MS analyses were carried out and the intermediate detected was compared with the previously published data for the enzymatic degradation of RTB. The results showed that one of the low molecular weight intermediates formed in the process was identical to those reported for peroxidase-degraded RTB, thus indicating that both enzymatic and photolytic mediated degradation of RTB may involve a common intermediate.

Enzymatic Degradation of Polyester-Nanoparticles by Lipases and Adsorption of Lipases on the Polyester-Nanoparticles

Enzymatic degradation tests of polymer in form of nanoparticle (NP) were used to study the biodegradation of two different types of polymers polytetramethylene adipitate (SP4/6) and polybutylene isophthalate (PBI) by two commercially available lipases. The two lipases, which are from the yeast Candida cylindracea (CcL) and Pseudomonas species (PsL) respectively, exhibited sufficient degradation activities both for the aliphatic model polyester SP4/6 and the aromatic model polyester PBI and the use of polyester NPs has dramatically shortened the duration of enzymatic degradation tests. It has also been noticed that the degradation percentage of the polyesters was in the range of 35-50%, probably due to the formation of low molecular weight intermediates that are not accessible to the enzymes. Since biodegradation of polymers is a surface process, the adsorption of lipases on the surface of polyester NPs may play an important role. In order to gain some insights into the adsorption process of enzymes on polymer NPs, the adsorption of CcL and PsL lipases on two hardly degradable polyesters polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) was investigated in this work. The adsorption of lipases on these polyester NPs showed a fast kinetic. Langmuir isotherms were found to be generally suitable to describe the adsorption of lipases on polyester NPs, especially at low lipase concentration under the experimental conditions. However, significant derivations from Langmuir isotherms were observed at high lipase concentrations.

19F NMR Studies of α-Synuclein Conformation and Fibrillation

Fibrils of the intrinsically disordered protein alpha-synuclein are hallmarks of Parkinson's disease. The fluorescent dye thioflavin T is often used to characterize fibrillation, but this assay may not provide quantitative information about structure and mechanism. To gain such information, we incorporated the 19F-labeled amino acid, 3-fluorotyrosine, into recombinant human alpha-synuclein at its endogenous tyrosine residues. Tyrosine 39 is in the positively charged N-terminal region of this 140-residue protein. The other three tyrosines, 125, 133, and 136, are near the C-terminus. 19F nuclear magnetic resonance spectroscopy was used to study several properties of labeled alpha-synuclein, including its conformation, conformational changes induced by urea, spermine, and sodium dodecyl sulfate (SDS), its interaction with SDS micelles, and the kinetics of fibril formation. The results show that the tyrosines are in disordered regions but that there is some structure near position 39 that is disrupted by urea. SDS binding alters the conformation near position 39, but the C-terminal tyrosines are disordered under all conditions. The NMR data also indicate that SDS-micelle-bound alpha-synuclein and the free protein exchange on the 10 ms time scale. Studies of fibrillation show the utility of 19F-labeled NMR. The data indicate that fibrillation is not accompanied by the formation of large quantities of low molecular weight intermediates. Although dye binding and 19F NMR data show that 1 mM SDS and 1 mM spermine accelerate aggregation compared to buffer alone, only the NMR data indicate that the species formed in SDS are smaller than those formed in buffer or buffer plus spermine. We conclude that 19F NMR spectroscopy is useful for obtaining residue-level, quantitative information about the structure, binding, and aggregation of alpha-synuclein.

Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability

Activated sludges are becoming more difficult to degrade in anaerobic digesters, due to the implementation of stricter nitrogen limits, longer sludge ages, and removal of primary sedimentation units. Thermal hydrolysis is a popular method to enhance degradability of long-age activated sludge, and involves pressure and heat treatment of the process fluid (150–160 °C saturated steam). However, as documented in this study, in a full-scale system, the use of thermal hydrolysis produces coloured, recalcitrant compounds that can have downstream impacts (e.g., failure of UV disinfection, and increased effluent nitrogen). The coloured compound formed during thermal hydrolysis was found to be melanoidins. These are coloured recalcitrant compounds produced by polymerisation of low molecular weight intermediates, such as carbohydrates and amino compounds at elevated temperature (Maillard reaction). By decreasing the THP operating temperature from 165 °C to 140 °C, THP effluent colour decreased from 12,677 mg-PtCo L −1 to 3837 mg-PtCo L −1. The change in THP operating temperature from 165 °C to 140 °C was shown to have no significant impact on anaerobic biodegradability of the sludge. The rate and extent of COD biodegradation remained largely unaffected by the temperature change with an average first order hydrolysis rate of 0.19 d −1 and conversion extent of 0.43 g-COD CH4 g-COD −1.

A continuous enzyme assay and characterisation of fructosyl amine oxidase enzymes (EC 1.5.3)

Enzymatic reversal of the Maillard reaction is a growing area of research. Fructosyl amine oxidase enzymes (EC 1.5.3) have attracted recent attention through demonstration of their ability to deglycate Amadori products, low molecular weight intermediates formed during the early stage of the Maillard reaction. Although stopped assays have been described, a bottleneck in current studies is the lack of continuous kinetic assays. Here, we describe the development of a continuous, coupled enzyme assay and its successful application to determining optimal storage conditions and the steady-state kinetic parameters of an enzyme from this group, amadoriase I. A K m app of 11 μM and a K cat app of 3.5 s −1 were determined using this assay using fructosyl propylamine as a substrate, which differ from previous reports. This method was also used to test the activity of two site-directed mutants of amadoriase I, H357N and S370A, which were found to be catalytically inactive.

Toxicity of fluoranthene and its biodegradation metabolites to aquatic organisms

The toxicity of nine stable products of the biodegradation of fluoranthene with the pure bacterial strain Pasteurella sp. IFA was studied. For their quantification, an improved analytical procedure with two-step liquid–liquid extraction, derivatisation and gas chromatographic-mass spectrometric detection was used. Growth inhibition and immobility tests for fluoranthene and its metabolites were carried out using algae ( Scenedesmus subspicatus), bacteria ( Pseudomonas putida) and crustaceans ( Daphnia magna and Thamnocephalus platyurus). Tests using the alga S. subspicatus revealed that with the exception of 9-hydroxyfluorene, which was only four times less toxic than fluoranthene, all the other metabolites were 37 to ∼3000 times less toxic than the parent material. P. putida cells were resistant to fluoranthene and its primary metabolites, but were inhibited by low molecular weight intermediates, especially benzoic acid. Fluoranthene was not toxic to T. Platyurus, but was toxic to D. magna. Its primary metabolites (including 9-fluorenone and 9-hydroxyfluorene) were toxic to D. magna, and a low molecular weight metabolite (2-carboxybenzaldehyde) was highly toxic to T. platyurus.

Biosynthesis of riboflavin. Single turnover kinetic analysis of GTP cyclohydrolase II.

GTP cyclohydrolase II catalyzes the conversion of GTP into a mixture of 2,5-diamino-6-ribosylamino-4(3H)-pyrimidinone 5'-phosphate (Compound 2), formate, and pyrophosphate. Moreover, GMP was recently shown to be formed as a minor product. The major product (Compound 2) serves as the first committed intermediate in the biosynthesis of the vitamin, riboflavin. Numerous pathogenic microorganisms are absolutely dependent on endogenous synthesis of riboflavin. The enzymes of this pathway are therefore potential drug targets, and mechanistic studies appear relevant for development of bactericidal inhibitors. Pre-steady state quenched flow analysis of GTP cyclohydrolase II shows the rate-determining step to be located at the beginning of the reaction sequence catalyzed by the enzyme. Thus, GTP is consumed at a rate constant of 0.064 s(-1), and the reaction product, Compound 2, is formed at an apparent rate constant of 0.062 s(-1). Stopped flow experiments monitored by multiwavelength photometry are well in line with these data. 2-Amino-5-formylamino-6-ribosylamino-4(3H)-pyrimidinone triphosphate can serve as substrate for GTP cyclohydrolase II but does not fulfill the criteria for a kinetically competent intermediate. A hypothetical reaction mechanism involves the slow formation of a phosphoguanosyl derivative of the enzyme under release of pyrophosphate. The covalently bound phosphoguanosyl moiety is proposed to undergo rapid hydrolytic release of formate from the imidazole ring and/or hydrolytic cleavage of the phosphodiester bond.

Degradation of polyvinyl alcohol (PVA) by homogeneous and heterogeneous photocatalysis applied to the photochemically enhanced Fenton reaction

The reaction mechanism of the oxidative degradation of polyvinyl alcohol (PVA) by the photochemically enhanced Fenton reaction was studied using a homogeneous (Fe2+(aq) + H2O2) and a heterogeneous reaction system (iron(III)-exchanged zeolite Y+ H2O2). In the homogeneous Fenton system, efficient degradation was observed in a batch reactor, equipped with a medium pressure mercury arc in a Pyrex envelope and employing 80% of the stoichiometric amount of H2O2 required for the total oxidation of PVA and a concentration ratio as low as I mole of iron(II) sulfate per 20 moles of PVA sub-units (C2H40). Model PVA polymers of three different molecular weights (15,000, 49,000 and 100,000 g mol(-1)) were found to follow identical degradation patterns. Strong experimental evidence supports the formation of supermacromolecules (MW: 1-5 x 10(6) g/mol) consisting of oxidized PVA and trapped iron(III) at an early reaction stage. Low molecular weight intermediates, such as oxalic acid, formic acid or formaldehyde were not found during PVA degradation in the homogeneous Fenton system, and we may deduce that the manifold of degradation reactions is mainly taking place within the super-macromolecules from which CO2 is directly released. However, in the heterogeneous Fenton system, the reaction behavior was found to be distinctly different: a decrease of the molecular weights of all three tested monodisperse PVA samples was observed by the broadening of the GPC-traces during irradiation, and oxalic acid was formed. The results lead to the mechanistic hypothesis that during the heterogeneous Fenton process, the cleavage of the PVA-chains may occur at random positions, the reactive centres being located inside the iron(III)-doped zeolite Y photocatalysts.

Oxidative Degradation of Polyvinyl Alcohol by the Photochemically Enhanced Fenton Reaction. Evidence for the Formation of Super-Macromolecules

The reaction mechanism of the oxidative degradation of polyvinyl alcohol (PVA) by the photochemically enhanced Fenton reaction has been studied. Fast and efficient degradation was observed in a batch reactor, using a medium pressure mercury arc in a Pyrex envelope and employing 80% of the stoichiometric amount of H2O2 required for the total oxidation of PVA and a concentration ratio as low as 1 mole of iron(II) sulfate per 20 moles of PVA sub-units (C2H4O) Model PVA polymers of three different molecular weights (15,000, 49,000 and 100,000 g mol−1) were found to follow identical degradation patterns. Strong experimental evidence supports the formation of super-macromolecules (MW: 1–5 × 106 g mol−1) consisting of oxidized PVA and trapped iron(III) at an early reaction stage. Low molecular weight intermediates, such as oxalic acid, formic acid or formaldehyde were not found during the PVA degradation, and we may deduce that the manifold of degradation reactions is mainly taking place within the super-macromolecules from which CO2 is directly released.

Formation of SnO2 Thin Film by Pyrolysis of a Photo-Cross-Linked Organotin Polymer

Micropatterns of a SnO2 thin film were obtained by lithographic photoirradiation followed by pyrolysis of thin films of an organotin polymer poly(4-((trimethylstannyl)methyl)styrene) (1). Irradiation of the polymer thin film by a KrF laser through a photomask followed by development gave a negative pattern of the insolubilized polymer. The following pyrolysis afforded a pattern of SnO2 without significant deformation of the pattern except for a reduction of the film thickness. The pyrolysis of the irradiated film without the development also gave a negative pattern of SnO2. The cross-linking of the organotin polymer caused by the irradiation was necessary both for lithographic processing and for SnO2 formation. In the conversion of the polymer to SnO2 during the pyrolysis, the cross-linked network seems to encapsulate low molecular weight intermediates, preventing their escape from the polymer film.

Formation of SnO2 by pyrolysis of a polymer network containing organotin groups

Pyrolytic conversion of poly(4-((trimethylstannyl)methyl)styrene) (1) film to SnO2 was studied. The pyrolysis at 500°C of the polymer film which was crosslinked by 248 nm light or electron beam irradiation afforded a SnO2 film. The crosslinking network formation is necessary for the conversion of 1 into SnO2 through the encapsulation of the low molecular weight intermediates to prevent their escape from the polymer film.